Proximal Nephron

PubMed Central

Zhuo, Jia L.; Li, Xiao C.

2013-01-01

The kidney plays a fundamental role in maintaining body salt and fluid balance and blood pressure homeostasis through the actions of its proximal and distal tubular segments of nephrons. However, proximal tubules are well recognized to exert a more prominent role than distal counterparts. Proximal tubules are responsible for reabsorbing approximately 65% of filtered load and most, if not all, of filtered amino acids, glucose, solutes, and low molecular weight proteins. Proximal tubules also play a key role in regulating acid-base balance by reabsorbing approximately 80% of filtered bicarbonate. The purpose of this review article is to provide a comprehensive overview of new insights and perspectives into current understanding of proximal tubules of nephrons, with an emphasis on the ultrastructure, molecular biology, cellular and integrative physiology, and the underlying signaling transduction mechanisms. The review is divided into three closely related sections. The first section focuses on the classification of nephrons and recent perspectives on the potential role of nephron numbers in human health and diseases. The second section reviews recent research on the structural and biochemical basis of proximal tubular function. The final section provides a comprehensive overview of new insights and perspectives in the physiological regulation of proximal tubular transport by vasoactive hormones. In the latter section, attention is particularly paid to new insights and perspectives learnt from recent cloning of transporters, development of transgenic animals with knockout or knockin of a particular gene of interest, and mapping of signaling pathways using microarrays and/or physiological proteomic approaches. PMID:23897681

Direct reprogramming of human bone marrow stromal cells into functional renal cells using cell-free extracts.

PubMed

Papadimou, Evangelia; Morigi, Marina; Iatropoulos, Paraskevas; Xinaris, Christodoulos; Tomasoni, Susanna; Benedetti, Valentina; Longaretti, Lorena; Rota, Cinzia; Todeschini, Marta; Rizzo, Paola; Introna, Martino; Grazia de Simoni, Maria; Remuzzi, Giuseppe; Goligorsky, Michael S; Benigni, Ariela

2015-04-14

The application of cell-based therapies in regenerative medicine is gaining recognition. Here, we show that human bone marrow stromal cells (BMSCs), also known as bone-marrow-derived mesenchymal cells, can be reprogrammed into renal proximal tubular-like epithelial cells using cell-free extracts. Streptolysin-O-permeabilized BMSCs exposed to HK2-cell extracts underwent morphological changes-formation of "domes" and tubule-like structures-and acquired epithelial functional properties such as transepithelial-resistance, albumin-binding, and uptake and specific markers E-cadherin and aquaporin-1. Transmission electron microscopy revealed the presence of brush border microvilli and tight intercellular contacts. RNA sequencing showed tubular epithelial transcript abundance and revealed the upregulation of components of the EGFR pathway. Reprogrammed BMSCs integrated into self-forming kidney tissue and formed tubular structures. Reprogrammed BMSCs infused in immunodeficient mice with cisplatin-induced acute kidney injury engrafted into proximal tubuli, reduced renal injury and improved function. Thus, reprogrammed BMSCs are a promising cell resource for future cell therapy. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

A novel angiotensin II type 1 receptor-associated protein induces cellular hypertrophy in rat vascular smooth muscle and renal proximal tubular cells.

PubMed

Guo, Deng-Fu; Tardif, Valerie; Ghelima, Karin; Chan, John S D; Ingelfinger, Julie R; Chen, XiangMei; Chenier, Isabelle

2004-05-14

Angiotensin II stimulates cellular hypertrophy in cultured vascular smooth muscle and renal proximal tubular cells. This effect is believed to be one of earliest morphological changes of heart and renal failure. However, the precise molecular mechanism involved in angiotensin II-induced hypertrophy is poorly understood. In the present study we report the isolation of a novel angiotensin II type 1 receptor-associated protein. It encodes a 531-amino acid protein. Its mRNA is detected in all human tissues examined but highly expressed in the human kidney, pancreas, heart, and human embryonic kidney cells as well as rat vascular smooth muscle and renal proximal tubular cells. Protein synthesis and relative cell size analyzed by flow cytometry studies indicate that overexpression of the novel angiotensin II type 1 receptor-associated protein induces cellular hypertrophy in cultured rat vascular smooth muscle and renal proximal tubular cells. In contrast, the hypertrophic effects was reversed in renal proximal tubular cell lines expressing the novel gene in the antisense orientation and its dominant negative mutant, which lacks the last 101 amino acids in its carboxyl-terminal tail. The hypertrophic effects are at least in part mediated via protein kinase B activation or cyclin-dependent kinase inhibitor, p27(kip1) protein expression level in vascular smooth muscle, and renal proximal tubular cells. Moreover, angiotensin II could not stimulate cellular hypertrophy in renal proximal tubular cells expressing the novel gene in the antisense orientation and its mutant. These findings may provide new molecular mechanisms to understand hypertrophic agents such as angiotensin II-induced cellular hypertrophy.

Tubular Obstruction Leads to Progressive Proximal Tubular Injury and Atubular Glomeruli in Polycystic Kidney Disease

PubMed Central

Galarreta, Carolina I.; Grantham, Jared J.; Forbes, Michael S.; Maser, Robin L.; Wallace, Darren P.; Chevalier, Robert L.

2015-01-01

In polycystic kidney disease (PKD), renal parenchyma is destroyed by cysts, hypothesized to obstruct nephrons. A signature of unilateral ureteral obstruction, proximal tubular atrophy leads to formation of atubular glomeruli. To determine whether this process occurs in PKD, kidneys from pcy mice (moderately progressive PKD), kidneys from cpk mice (rapidly progressive PKD), and human autosomal dominant PKD were examined in early and late stages. Integrity of the glomerulotubular junction and proximal tubular mass were determined in sections stained with Lotus tetragonolobus lectin. Development of proximal tubular atrophy and atubular glomeruli was determined in serial sections of individual glomeruli. In pcy mice, most glomerulotubular junctions were normal at 20 weeks, but by 30 weeks, 56% were atrophic and 25% of glomeruli were atubular; glomerulotubular junction integrity decreased with increasing cyst area (r = 0.83, P < 0.05). In cpk mice, all glomerulotubular junctions were normal at 10 days, but by 19 days, 26% had become abnormal. In early-stage autosomal dominant PKD kidneys, 50% of glomeruli were atubular or attached to atrophic tubules; in advanced disease, 100% were abnormal. Thus, proximal tubular injury in cystic kidneys closely parallels that observed with ureteral obstruction. These findings support the hypothesis that, in renal cystic disorders, cyst-dependent obstruction of medullary and cortical tubules initiates a process culminating in widespread destruction of proximal convoluted tubules at the glomerulotubular junction. PMID:24815352

Indoxyl Sulfate Induces Apoptosis and Hypertrophy in Human Kidney Proximal Tubular Cells.

PubMed

Ellis, Robert J; Small, David M; Ng, Keng Lim; Vesey, David A; Vitetta, Luis; Francis, Ross S; Gobe, Glenda C; Morais, Christudas

2018-06-01

Indoxyl sulfate (IS) is a protein-bound uremic toxin that accumulates in patients with declining kidney function. Although generally thought of as a consequence of declining kidney function, emerging evidence demonstrates direct cytotoxic role of IS on endothelial cells and cardiomyocytes, largely through the expression of pro-inflammatory and pro-fibrotic factors. The direct toxicity of IS on human kidney proximal tubular epithelial cells (PTECs) remains a matter of debate. The current study explored the effect of IS on primary cultures of human PTECs and HK-2, an immortalized human PTEC line. Pathologically relevant concentrations of IS induced apoptosis and increased the expression of the proapoptotic molecule Bax in both cell types. IS impaired mitochondrial metabolic activity and induced cellular hypertrophy. Furthermore, statistically significant upregulation of pro-fibrotic (transforming growth factor-β, fibronectin) and pro-inflammatory molecules (interleukin-6, interleukin-8, and tumor necrosis factor-α) in response to IS was observed. Albumin had no influence on the toxicity of IS. The results of this study suggest that IS directly induced a pro-inflammatory and pro-fibrotic phenotype in proximal tubular cells. In light of the associated apoptosis, hypertrophy, and metabolic dysfunction, this study demonstrates that IS may play a role in the progression of chronic kidney disease.

Human mesenchymal stromal cells transplanted into mice stimulate renal tubular cells and enhance mitochondrial function.

PubMed

Perico, Luca; Morigi, Marina; Rota, Cinzia; Breno, Matteo; Mele, Caterina; Noris, Marina; Introna, Martino; Capelli, Chiara; Longaretti, Lorena; Rottoli, Daniela; Conti, Sara; Corna, Daniela; Remuzzi, Giuseppe; Benigni, Ariela

2017-10-17

Mesenchymal stromal cells (MSCs) are renoprotective and drive regeneration following injury, although cellular targets of such an effect are still ill-defined. Here, we show that human umbilical cord (UC)-MSCs transplanted into mice stimulate tubular cells to regain mitochondrial mass and function, associated with enhanced microtubule-rich projections that appear to mediate mitochondrial trafficking to create a reparative dialogue among adjacent tubular cells. Treatment with UC-MSCs in mice with cisplatin-induced acute kidney injury (AKI) regulates mitochondrial biogenesis in proximal tubuli by enhancing PGC1α expression, NAD + biosynthesis and Sirtuin 3 (SIRT3) activity, thus fostering antioxidant defenses and ATP production. The functional role of SIRT3 in tubular recovery is highlighted by data that in SIRT3-deficient mice with AKI, UC-MSC treatment fails to induce renoprotection. These data document a previously unrecognized mechanism through which UC-MSCs facilitate renal repair, so as to induce global metabolic reprogramming of damaged tubular cells to sustain energy supply.Mesenchymal stromal cells drive renal regeneration following injury. Here, the authors show that human mesenchymal stromal cells, when transplanted into mice with acute kidney injury, stimulate renal tubular cell growth and enhance mitochondrial function via SIRT3.

MDM2 prevents spontaneous tubular epithelial cell death and acute kidney injury

PubMed Central

Thomasova, Dana; Ebrahim, Martrez; Fleckinger, Kristina; Li, Moying; Molnar, Jakob; Popper, Bastian; Liapis, Helen; Kotb, Ahmed M; Siegerist, Florian; Endlich, Nicole; Anders, Hans-Joachim

2016-01-01

Murine double minute-2 (MDM2) is an E3-ubiquitin ligase and the main negative regulator of tumor suppressor gene p53. MDM2 has also a non-redundant function as a modulator of NF-kB signaling. As such it promotes proliferation and inflammation. MDM2 is highly expressed in the unchallenged tubular epithelial cells and we hypothesized that MDM2 is necessary for their survival and homeostasis. MDM2 knockdown by siRNA or by genetic depletion resulted in demise of tubular cells in vitro. This phenotype was completely rescued by concomitant knockdown of p53, thus suggesting p53 dependency. In vivo experiments in the zebrafish model demonstrated that the tubulus cells of the larvae undergo cell death after the knockdown of mdm2. Doxycycline-induced deletion of MDM2 in tubular cell-specific MDM2-knockout mice Pax8rtTa-cre; MDM2f/f caused acute kidney injury with increased plasma creatinine and blood urea nitrogen and sharp decline of glomerular filtration rate. Histological analysis showed massive swelling of renal tubular cells and later their loss and extensive tubular dilation, markedly in proximal tubules. Ultrastructural changes of tubular epithelial cells included swelling of the cytoplasm and mitochondria with the loss of cristae and their transformation in the vacuoles. The pathological phenotype of the tubular cell-specific MDM2-knockout mouse model was completely rescued by co-deletion of p53. Tubular epithelium compensates only partially for the cell loss caused by MDM2 depletion by proliferation of surviving tubular cells, with incomplete MDM2 deletion, but rather mesenchymal healing occurs. We conclude that MDM2 is a non-redundant survival factor for proximal tubular cells by protecting them from spontaneous p53 overexpression-related cell death. PMID:27882940

Elevated oxidized glutathione in cystinotic proximal tubular epithelial cells.

PubMed

Wilmer, Martijn J G; de Graaf-Hess, Adriana; Blom, Henk J; Dijkman, Henry B P M; Monnens, Leo A; van den Heuvel, Lambertus P; Levtchenko, Elena N

2005-11-18

Cystinosis, the most frequent cause of inborn Fanconi syndrome, is characterized by the lysosomal cystine accumulation, caused by mutations in the CTNS gene. To elucidate the pathogenesis of cystinosis, we cultured proximal tubular cells from urine of cystinotic patients (n = 9) and healthy controls (n = 9), followed by immortalization with human papilloma virus (HPV E6/E7). Obtained cell lines displayed basolateral polarization, alkaline phosphatase activity, and presence of aminopeptidase N (CD-13) and megalin, confirming their proximal tubular origin. Cystinotic cell lines exhibited elevated cystine levels (0.86 +/- 0.95 nmol/mg versus 0.09 +/- 0.01 nmol/mg protein in controls, p = 0.03). Oxidized glutathione was elevated in cystinotic cells (1.16 +/- 0.83 nmol/mg versus 0.29 +/- 0.18 nmol/mg protein, p = 0.04), while total glutathione, free cysteine, and ATP contents were normal in these cells. In conclusion, elevated oxidized glutathione in cystinotic proximal tubular epithelial cell lines suggests increased oxidative stress, which may contribute to tubular dysfunction in cystinosis.

[Acute renal failure and proximal renal tubular dysfuntion in a patient with acquired immunodeficiency syndrome treated with tenofovir].

PubMed

de la Prada, F J; Prados, A M; Tugores, A; Uriol, M; Saus, C; Morey, A

2006-01-01

Tenofovir, a new nucleotide reverse transcriptase inhibitor that has good antiviral activity against drug-resistant strains of HIV, is structurally similar to cidofovir and adefovir and seems to be less nephrotoxic. Nephrotoxicity of cidofovir and adefovir is well established and they have been associated with increase for acute renal insufficiency due to tubular toxicity, possibly induced via mitochondrial deplection. Tenofovir has little mithocondrial toxicity in in vitro assays and early clinical studies. However some cases of renal tubular dysfuntion and renal failure related to tenofovir treatment have been published recently. Increased plasma concentrations of didanosine were observed after the adition of tenofovir and protease inhibitors can interact with the renal transport of organic anions leading to proximal tubular intracellular accumulation of tenofovir, yield Fanconi syndrome-type tubulopathy. We present a case in wich acute renal failure and proximal tubular dysfunction developed after therapy with tenofovir in a patiente with HIV who had suffered from complications of didanosine treatment. Although nephrotoxicity certainly occurs much less frequently with tenofovir that it does with other nuclotide analogues, use of tenofovir by patients with underlying renal disfuntion, for longer durations and/or associated with didanosine or lopinavir-ritonavir, might be associated with renal toxicity. Patients receiving tenofovir must be monitored for sings of tubulopathy with simple tests such us glycosuria, phosphaturia, proteinuria, phosphoremia and renal function, as well as assessment for signs of mithocondrial toxicity when a nucleoside analogue is being administered, and therapy should be stopped to avoid the risk of definitive renal failure.

Zea mays L. extracts modify glomerular function and potassium urinary excretion in conscious rats.

PubMed

Velazquez, D V O; Xavier, H S; Batista, J E M; de Castro-Chaves, C

2005-05-01

Diuretic and uricosuric properties have traditionally been attributed to corn silk, stigma/style of Zea mays L. Although the diuretic effect was confirmed, studies of the plant's effects on renal function or solute excretion were lacking. Thus, we studied the effects of corn silk aqueous extract on the urinary excretion of water, Na+, K+, and uric acid. Glomerular and proximal tubular function and Na+ tubular handling were also studied. Conscious, unrestrained adult male rats were housed in individual metabolic cages (IMC) with continuous urine collection for 5 and 3 h, following two protocols. The effects of 25, 50, 200, 350, and 500 mg/kg body wt. corn silk extract on urine volume plus Na+ and K+ excretions were studied in water-loaded conscious rats (2.5 ml/100 g body wt.) in the IMC for 5 h (Protocol 1). Kaliuresis was observed with doses of 350 (100.42 +/- 22.32-120.28 +/- 19.70 microEq/5 h/100 g body wt.; n = 13) and 500 mg/kg body wt. (94.97+/- 29.30-134.32 +/- 39.98 microEq/5h/100 g body wt.; n = 12; p<0.01), and the latter dose resulted in diuresis as well (1.98 +/- 0.44-2.41 +/- 0.41 ml/5 h/100 g body wt.; n = 12; p<0.05). The effects of a 500 mg/kg body wt. dose of corn silk extract on urine volume, Na+, K+ and uric acid excretions, and glomerular and proximal tubular function, were measured respectively by creatinine (Cler) and Li+ (ClLi) clearances and Na+ tubular handling, in water-loaded rats (5 ml/100 g body wt.) in the IMC for 3 h (Protocol 2). Clcr (294.6 +/- 73.2, n = 12, to 241.7 +/- 48.0 microl/ min/100 g body wt.; n = 13; p<0.05) and the Na+ filtered load (41.9 +/- 10.3, n = 12, to 34.3 +/- .8, n = 13, p<0.05) decreased and ClLi and Na+ excretion were unchanged, while K+ excretion (0.1044 +/- 0.0458, n=12, to 0.2289 +/- 0.0583 microEq/min/100 body wt.; n = 13; p<0.001) increased. For Na+ tubular handling, the fractional proximal tubular reabsorption (91.5 +/- 3.5, n = 12, to 87.5 +/- 3.4%; n = 13; p<0.01) decreased, and both fractional distal reabsorptions--I and II--increased (96.5 +/- 1.5, n = 12, to 97.8 +/- 0.9%; n = 13; p<0.01; and 8.2 +/- 3.5, n = 12, to 12.2 +/- 3.4%, n = 13, p<0.01, respectively). To summarize, in water-loaded conscious rats (2.5 ml/100 body wt.), corn silk aqueous extract is diuretic at a dose of 500 mg/kg body wt. and kaliuretic at doses of 350 and 500 mg/kg body wt. In water-loaded conscious rats (5.0 ml/100 g body wt.), corn silk aqueous extract is kaliuretic at a dose of 500 mg/kg body wt., but glomerular filtration and filtered load decrease without affecting proximal tubular function, Na+, or uric acid excretion.

mTOR Regulates Endocytosis and Nutrient Transport in Proximal Tubular Cells.

PubMed

Grahammer, Florian; Ramakrishnan, Suresh K; Rinschen, Markus M; Larionov, Alexey A; Syed, Maryam; Khatib, Hazim; Roerden, Malte; Sass, Jörn Oliver; Helmstaedter, Martin; Osenberg, Dorothea; Kühne, Lucas; Kretz, Oliver; Wanner, Nicola; Jouret, Francois; Benzing, Thomas; Artunc, Ferruh; Huber, Tobias B; Theilig, Franziska

2017-01-01

Renal proximal tubular cells constantly recycle nutrients to ensure minimal loss of vital substrates into the urine. Although most of the transport mechanisms have been discovered at the molecular level, little is known about the factors regulating these processes. Here, we show that mTORC1 and mTORC2 specifically and synergistically regulate PTC endocytosis and transport processes. Using a conditional mouse genetic approach to disable nonredundant subunits of mTORC1, mTORC2, or both, we showed that mice lacking mTORC1 or mTORC1/mTORC2 but not mTORC2 alone develop a Fanconi-like syndrome of glucosuria, phosphaturia, aminoaciduria, low molecular weight proteinuria, and albuminuria. Interestingly, proteomics and phosphoproteomics of freshly isolated kidney cortex identified either reduced expression or loss of phosphorylation at critical residues of different classes of specific transport proteins. Functionally, this resulted in reduced nutrient transport and a profound perturbation of the endocytic machinery, despite preserved absolute expression of the main scavenger receptors, MEGALIN and CUBILIN. Our findings highlight a novel mTOR-dependent regulatory network for nutrient transport in renal proximal tubular cells. Copyright © 2016 by the American Society of Nephrology.

The Role of “Leakage” of Tubular Fluid in Anuria Due to Mercury Poisoning*

PubMed Central

Bank, Norman; Mutz, Bertrand F.; Aynedjian, Hagop S.

1967-01-01

The role of “leakage” of tubular fluid in anuria produced by mercury poisoning was studied in rats by micropuncture techniques. After an initial brisk diuresis, almost all animals were completely anuric 24 hours after HgCl2 injection. Lissamine green injected intravenously in the early stage of anuria appeared in the beginning of the proximal tubule, but the color became progressively lighter as the dye traversed the proximal convolutions. The dye was barely visible in the terminal segments of the proximal tubule; it did not appear at all in the distal tubules. These observations suggest that the proximal epithelium had become abnormally permeable to Lissamine green. Tubular fluid to plasma inulin (TF/PIn) ratios and inulin clearance were measured in individual nephrons at three sites: early proximal tubule, late proximal tubule, and distal tubule. It was found that TF/PIn ratios were abnormally low in the late proximal and distal tubules. Inulin clearance was normal at the beginning of the proximal tubule but fell by more than 60% by the late proximal convolutions. Thus, the proximal tubule had also become permeable to inulin. We conclude from these observations that anuria in mercury poisoning can occur in the presence of a normal glomerular filtration rate. The absence of urine flow appears to be due to complete absorption of the filtrate through an excessively permeable tubular epithelium. The driving force affecting this fluid absorption is probably the colloid oncotic pressure of the peritubular capillary blood. Images PMID:6025476

Renal Tubular Cell Mitochondrial Dysfunction Occurs Despite Preserved Renal Oxygen Delivery in Experimental Septic Acute Kidney Injury

PubMed Central

Pollen, Sean; Greco, Elisabetta; Courtneidge, Holly; Hall, Andrew M.; Duchen, Michael R.; Tam, Frederick W. K.; Unwin, Robert J.; Singer, Mervyn

2018-01-01

Objective: To explain the paradigm of significant renal functional impairment despite preserved hemodynamics and histology in sepsis-induced acute kidney injury. Design: Prospective observational animal study. Setting: University research laboratory. Subjects: Male Wistar rats. Intervention: Using a fluid-resuscitated sublethal rat model of fecal peritonitis, changes in renal function were characterized in relation to global and renal hemodynamics, and histology at 6 and 24 hours (n = 6–10). Sham-operated animals were used as comparison (n = 8). Tubular cell mitochondrial function was assessed using multiphoton confocal imaging of live kidney slices incubated in septic serum. Measurements and Main Results: By 24 hours, serum creatinine was significantly elevated with a concurrent decrease in renal lactate clearance in septic animals compared with sham-operated and 6-hour septic animals. Renal uncoupling protein-2 was elevated in septic animals at 24 hours although tubular cell injury was minimal and mitochondrial ultrastructure in renal proximal tubular cells preserved. There was no significant change in global or renal hemodynamics and oxygen delivery/consumption between sham-operated and septic animals at both 6- and 24-hour timepoints. In the live kidney slice model, mitochondrial dysfunction was seen in proximal tubular epithelial cells incubated with septic serum with increased production of reactive oxygen species, and decreases in nicotinamide adenine dinucleotide and mitochondrial membrane potential. These effects were prevented by coincubation with the reactive oxygen species scavenger, 4-hydroxy-2,2,6,6-tetramethyl-piperidin-1-oxyl. Conclusions: Renal dysfunction in sepsis occurs independently of hemodynamic instability or structural damage. Mitochondrial dysfunction mediated by circulating mediators that induce local oxidative stress may represent an important pathophysiologic mechanism. PMID:29293148

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Zhenzhou, E-mail: jiangcpu@yahoo.com.cn; Bao, Qingli, E-mail: bao_ql@126.com; Sun, Lixin, E-mail: slxcpu@126.com

This report describes an investigation of the pathological mechanism of acute renal failure caused by toxic tubular necrosis after treatment with aristolochic acid I (AAI) in Sprague–Dawley (SD) rats. The rats were gavaged with AAI at 0, 5, 20, or 80 mg/kg/day for 7 days. The pathologic examination of the kidneys showed severe acute tubular degenerative changes primarily affecting the proximal tubules. Supporting these results, we detected significantly increased concentrations of blood urea nitrogen (BUN) and creatinine (Cr) in the rats treated with AAI, indicating damage to the kidneys. Ultrastructural examination showed that proximal tubular mitochondria were extremely enlarged andmore » dysmorphic with loss and disorientation of their cristae. Mitochondrial function analysis revealed that the two indicators for mitochondrial energy metabolism, the respiratory control ratio (RCR) and ATP content, were reduced in a dose-dependent manner after AAI treatment. The RCR in the presence of substrates for complex I was reduced more significantly than in the presence of substrates for complex II. In additional experiments, the activity of respiratory complex I, which is partly encoded by mitochondrial DNA (mtDNA), was more significantly impaired than that of respiratory complex II, which is completely encoded by nuclear DNA (nDNA). A real-time PCR assay revealed a marked reduction of mtDNA in the kidneys treated with AAI. Taken together, these results suggested that mtDNA depletion and respiratory chain defects play critical roles in the pathogenesis of kidney injury induced by AAI, and that the same processes might contribute to aristolochic acid-induced nephrotoxicity in humans. -- Highlights: ► AAI-induced acute renal failure in rats and the proximal tubule was the target. ► Tubular mitochondria were morphologically aberrant in ultrastructural examination. ► AAI impair mitochondrial bioenergetic function and mtDNA replication.« less

Impaired Urine Dilution Capability in HIV Stable Patients

PubMed Central

Belloso, Waldo H.; de Paz Sierra, Mariana; Navarro, Matilde; Sanchez, Marisa L.; Perelsztein, Ariel G.; Musso, Carlos G.

2014-01-01

Renal disease is a well-recognized complication among patients with HIV infection. Viral infection itself and the use of some antiretroviral drugs contribute to this condition. The thick ascending limb of Henle's loop (TALH) is the tubule segment where free water clearance is generated, determining along with glomerular filtration rate the kidney's ability to dilute urine. Objective. We analyzed the function of the proximal tubule and TALH in patients with HIV infection receiving or not tenofovir-containing antiretroviral treatment in comparison with healthy seronegative controls, by applying a tubular physiological test, hyposaline infusion test (Chaimowitz' test). Material & Methods. Chaimowitz' test was performed on 20 HIV positive volunteers who had normal renal functional parameters. The control group included 10 healthy volunteers. Results. After the test, both HIV groups had a significant reduction of serum sodium and osmolarity compared with the control group. Free water clearance was lower and urine osmolarity was higher in both HIV+ groups. Proximal tubular function was normal in both studied groups. Conclusion. The present study documented that proximal tubule sodium reabsorption was preserved while free water clearance and maximal urine dilution capability were reduced in stable HIV patients treated or not with tenofovir. PMID:24800076

Insulin's acute effects on glomerular filtration rate correlate with insulin sensitivity whereas insulin's acute effects on proximal tubular sodium reabsorption correlation with salt sensitivity in normal subjects.

PubMed

ter Maaten, J C; Bakker, S J; Serné, E H; ter Wee, P M; Donker, A J; Gans, R O

1999-10-01

Insulin induces sodium retention by increasing distal tubular sodium reabsorption. Opposite effects of insulin to offset insulin-induced sodium retention are supposedly increases in glomerular filtration rate (GFR) and decreases in proximal tubular sodium reabsorption. Defects in these opposing effects could link insulin resistance to blood-pressure elevation and salt sensitivity. We assessed the relationship between the effects of sequential physiological and supraphysiological insulin dosages (50 and 150 mU/kg/h) on renal sodium handling, and insulin sensitivity and salt sensitivity using the euglycaemic clamp technique and clearances of [131I]hippuran, [125I]iothalamate, sodium, and lithium in 20 normal subjects displaying a wide range of insulin sensitivity. Time-control experiments were performed in the same subjects. Salt sensitivity was determined using a diet method. During the successive insulin infusions, GFR increased by 5.9% (P = 0.003) and 10.9% (P<0.001), while fractional sodium excretion decreased by 34 and 50% (both P<0.001). Distal tubular sodium reabsorption increased and proximal tubular sodium reabsorption decreased. Insulin sensitivity correlated with changes in GFR during physiological (r = 0.60, P = 0.005) and supraphysiological (r = 0.58, P = 0.007) hyperinsulinaemia, but not with changes in proximal tubular sodium reabsorption. Salt sensitivity correlated with changes in proximal tubular sodium reabsorption (r = 0.49, P = 0.028), but not in GFR, during physiological hyperinsulinaemia. Neither insulin sensitivity or salt sensitivity correlated with changes in overall fractional sodium excretion. Insulin sensitivity and salt sensitivity correlate with changes in different elements of renal sodium handling, but not with overall sodium excretion, during insulin infusion. The relevance for blood pressure regulation remains to be proved.

Evolving concepts on regulation and function of renin in distal nephron

PubMed Central

Prieto, Minolfa C.; Gonzalez, Alexis A.

2012-01-01

Sustained stimulation of the intrarenal/intratubular renin–angiotensin system in a setting of elevated arterial pressure elicits renal vasoconstriction, increased sodium reabsorption, proliferation, fibrosis, and eventual renal injury. Activation of luminal AT1 receptors in proximal and distal nephron segments by local Ang II formation stimulates various transport systems. Augmented angiotensinogen (AGT) production by proximal tubule cells increases AGT secretion contributing to increased proximal Ang II levels and leading to spillover of AGT into the distal nephron segments, as reflected by increased urinary AGT excretion. The increased distal delivery of AGT provides substrate for renin, which is expressed in principal cells of the collecting tubule and collecting ducts, and is also stimulated by AT1 receptor activation. Renin and prorenin are secreted into the tubular lumen and act on the AGT delivered from the proximal tubule to form more Ang I. The catalytic actions of renin and or prorenin may be enhanced by binding to prorenin receptors on the intercalated cells or soluble prorenin receptor secreted into the tubular fluid. There is also increased luminal angiotensin converting enzyme in collecting ducts facilitating Ang II formation leading to stimulation of sodium reabsorption via sodium channel and sodium/chloride co-transporter. Thus, increased collecting duct renin contributes to Ang II-dependent hypertension by augmenting distal nephron intra-tubular Ang II formation leading to sustained stimulation of sodium reabsorption and progression of hypertension. PMID:22990760

Increased renal tubular sodium reabsorption during exercise-induced hypervolemia in humans

NASA Technical Reports Server (NTRS)

Nagashima, K.; Wu, J.; Kavouras, S. A.; Mack, G. W.

2001-01-01

We tested the hypothesis that renal tubular Na(+) reabsorption increased during the first 24 h of exercise-induced plasma volume expansion. Renal function was assessed 1 day after no-exercise control (C) or intermittent cycle ergometer exercise (Ex, 85% of peak O(2) uptake) for 2 h before and 3 h after saline loading (12.5 ml/kg over 30 min) in seven subjects. Ex reduced renal blood flow (p-aminohippurate clearance) compared with C (0.83 +/- 0.12 vs. 1.49 +/- 0.24 l/min, P < 0.05) but did not influence glomerular filtration rates (97 +/- 10 ml/min, inulin clearance). Fractional tubular reabsorption of Na(+) in the proximal tubules was higher in Ex than in C (P < 0.05). Saline loading decreased fractional tubular reabsorption of Na(+) from 99.1 +/- 0.1 to 98.7 +/- 0.1% (P < 0.05) in C but not in Ex (99.3 +/- 0.1 to 99.4 +/- 0.1%). Saline loading reduced plasma renin activity and plasma arginine vasopressin levels in C and Ex, although the magnitude of decrease was greater in C (P < 0.05). These results indicate that, during the acute phase of exercise-induced plasma volume expansion, increased tubular Na(+) reabsorption is directed primarily to the proximal tubules and is associated with a decrease in renal blood flow. In addition, saline infusion caused a smaller reduction in fluid-regulating hormones in Ex. The attenuated volume-regulatory response acts to preserve distal tubular Na(+) reabsorption during saline infusion 24 h after exercise.

Regulation of proximal tubular cell differentiation and proliferation in primary culture by matrix stiffness and ECM components.

PubMed

Chen, Wan-Chun; Lin, Hsi-Hui; Tang, Ming-Jer

2014-09-15

To explore whether matrix stiffness affects cell differentiation, proliferation, and transforming growth factor (TGF)-β1-induced epithelial-mesenchymal transition (EMT) in primary cultures of mouse proximal tubular epithelial cells (mPTECs), we used a soft matrix made from monomeric collagen type I-coated polyacrylamide gel or matrigel (MG). Both kinds of soft matrix benefited primary mPTECs to retain tubular-like morphology with differentiation and growth arrest and to evade TGF-β1-induced EMT. However, the potent effect of MG on mPTEC differentiation was suppressed by glutaraldehyde-induced cross-linking and subsequently stiffening MG or by an increasing ratio of collagen in the soft mixed gel. Culture media supplemented with MG also helped mPTECs to retain tubular-like morphology and a differentiated phenotype on stiff culture dishes as soft MG did. We further found that the protein level and activity of ERK were scaled with the matrix stiffness. U-0126, a MEK inhibitor, abolished the stiff matrix-induced dedifferentiation and proliferation. These data suggest that the ERK signaling pathway plays a vital role in matrix stiffness-regulated cell growth and differentiation. Taken together, both compliant property and specific MG signals from the matrix are required for the regulation of epithelial differentiation and proliferation. This study provides a basic understanding of how physical and chemical cues derived from the extracellular matrix regulate the physiological function of proximal tubules and the pathological development of renal fibrosis. Copyright © 2014 the American Physiological Society.

Renal handling of sodium and water in the hypothyroid rat

PubMed Central

Michael, Ulrich F.; Barenberg, Robert L.; Chavez, Rafaelita; Vaamonde, Carlos A.; Papper, Solomon

1972-01-01

Hypothyroid rats were examined with conventional renal clearance and micropuncture techniques to elicit the mechanism and site within the nephron responsible for the increased salt and water excretion observed in these animals. When compared with age-matched control rats, a decrease in inulin clearance of 30% (P < 0.001) and in Hippuran clearance of 32% (P < 0.005) was observed in the hypothyroid rats. Absolute excretion of sodium and water was increased 3-fold (P < 0.02) and 2-fold (P < 0.025), respectively, while fractional excretion of sodium and water was increased 4.3-fold (P < 0.02) and 2.9-fold (P < 0.05), respectively, in the hypothyroid animals. Fractional proximal reabsorption of sodium as assessed from proximal tubular fluid to plasma ratios of inulin ([TF/P]IN) was found to be decreased by 28% (P < 0.001) in the hypothyroid rats. Superficial single nephron filtration rate was reduced proportionately to the decrease in total filtration rate in the hypothyroid rats. These data indicate that the proximal tubule is one of the sites of diminished sodium and water reabsorption in the hypothyroid rat. The data also suggest that the observed decrease in glomerular filtration rate in the hypothyroid animals is not caused by a decrease in the number of functioning nephrons and that the observed increase in sodium and water excretion is not caused by a redistribution of filtrate from juxtamedullary to superficial nephrons. Although the exact mechanisms of the observed changes in proximal tubular function remain unknown, the data suggest that they are probably related to the lack of thyroid hormone. Whatever their mechanism, it appears that the enhanced sodium and water excretion observed in the hypothyroid animals must be determined by further reduction in tubular sodium reabsorption in the distal nephron. PMID:5024038

Drp1-dependent mitophagy protects against cisplatin-induced apoptosis of renal tubular epithelial cells by improving mitochondrial function

PubMed Central

Qi, Jia; Duan, Suyan; Huang, Zhimin; Zhang, Chengning; Wu, Lin; Zeng, Ming; Zhang, Bo; Wang, Ningning; Mao, Huijuan; Zhang, Aihua; Xing, Changying; Yuan, Yanggang

2017-01-01

Cisplatin chemotherapy often causes acute kidney injury (AKI) in cancer patients. There is increasing evidence that mitochondrial dysfunction plays an important role in cisplatin-induced nephrotoxicity. Degradation of damaged mitochondria is carried out by mitophagy. Although mitophagy is considered of particular importance in protecting against AKI, little is known of the precise role of mitophagy and its molecular mechanisms during cisplatin-induced nephrotoxicity. Also, evidence that activation of mitophagy improved mitochondrial function is lacking. Furthermore, several evidences have shown that mitochondrial fission coordinates with mitophagy. The aim of this study was to investigate whether activation of mitophagy protects against mitochondrial dysfunction and renal proximal tubular cells injury during cisplatin treatment. The effect of mitochondrial fission on mitophagy was also investigated. In cultured human renal proximal tubular cells, we observed that 3-methyladenine, a pharmacological inhibitor of autophagy, blocked mitophagy and exacerbated cisplatin-induced mitochondrial dysfunction and cells injury. In contrast, autophagy activator rapamycin enhanced mitophagy and protected against the harmful effects of cisplatin on mitochondrial function and cells viability. Suppression of mitochondrial fission by knockdown of its main regulator dynamin-related protein-1 (Drp1) decreased cisplatin-induced mitophagy. Meanwhile, Drp1 suppression protected against cisplatin-induced cells injury by inhibiting mitochondrial dysfunction. Our results provide evidence that Drp1-depedent mitophagy has potential as renoprotective targets for the treatment of cisplatin-induced AKI. PMID:28423497

IgA-kappa type multiple myeloma affecting proximal and distal renal tubules.

PubMed

Minemura, K; Ichikawa, K; Itoh, N; Suzuki, N; Hara, M; Shigematsu, S; Kobayashi, H; Hiramatsu, K; Hashizume, K

2001-09-01

A 45-year-old male was admitted because of chest pain, lumbago, and bilateral ankle pain. Examination disclosed hypophosphatemic osteomalacia, acquired Fanconi syndrome, and abnormalities in distal nephron such as distal renal tubular acidosis and renal diabetes insipidus. Further exploration revealed IgA kappa multiple myeloma excreting urinary Bence Jones protein (kappa-light chain). Renal biopsy revealed thick basement membranes and elec-tron-dense crystals in proximal tubular epithelial cells. Immunofluorescent studies revealed deposition of kappa-light chain in renal tubular epithelial cells that caused the renal tubular damage. Although the osteomalacia was relieved by medical treatment, the urinary Bence Jones protein and the renal tubular defects were not improved by the chemotherapy for the myeloma. The patient died of exacerbation of multiple myeloma at 50 years of age.

Histone deacetylase inhibitors protect against cisplatin-induced acute kidney injury by activating autophagy in proximal tubular cells.

PubMed

Liu, Jing; Livingston, Man J; Dong, Guie; Tang, Chengyuan; Su, Yunchao; Wu, Guangyu; Yin, Xiao-Ming; Dong, Zheng

2018-02-23

Histone deacetylase inhibitors (HDACi) have therapeutic effects in models of various renal diseases including acute kidney injury (AKI); however, the underlying mechanism remains unclear. Here we demonstrate that two widely tested HDACi (suberoylanilide hydroxamic acid (SAHA) and trichostatin A (TSA)) protect the kidneys in cisplatin-induced AKI by enhancing autophagy. In cultured renal proximal tubular cells, SAHA and TSA enhanced autophagy during cisplatin treatment. We further verified the protective effect of TSA against cisplatin-induced apoptosis in these cells. Notably, inhibition of autophagy by chloroquine or by autophagy gene 7 (Atg7) ablation diminished the protective effect of TSA. In mice, TSA increased autophagy in renal proximal tubules and protected against cisplatin-induced AKI. The in vivo effect of TSA was also abolished by chloroquine and by Atg7 knockout specifically from renal proximal tubules. Mechanistically, TSA stimulated AMPK and inactivated mTOR during cisplatin treatment of proximal tubule cells and kidneys in mice. Together, these results suggest that HDACi may protect kidneys by activating autophagy in proximal tubular cells.

Mixed organic solvents induce renal injury in rats.

PubMed

Qin, Weisong; Xu, Zhongxiu; Lu, Yizhou; Zeng, Caihong; Zheng, Chunxia; Wang, Shengyu; Liu, Zhihong

2012-01-01

To investigate the injury effects of organic solvents on kidney, an animal model of Sprague-Dawley (SD) rats treated with mixed organic solvents via inhalation was generated and characterized. The mixed organic solvents consisted of gasoline, dimethylbenzene and formaldehyde (GDF) in the ratio of 2:2:1, and were used at 12,000 PPM to treat the rats twice a day, each for 3 hours. Proteinuria appeared in the rats after exposure for 5-6 weeks. The incidences of proteinuria in male and female rats after exposure for 12 weeks were 43.8% (7/16) and 25% (4/16), respectively. Urinary N-Acetyl-β-(D)-Glucosaminidase (NAG) activity was increased significantly after exposure for 4 weeks. Histological examination revealed remarkable injuries in the proximal renal tubules, including tubular epithelial cell detachment, cloud swelling and vacuole formation in the proximal tubular cells, as well as proliferation of parietal epithelium and tubular reflux in glomeruli. Ultrastructural examination found that brush border and cytoplasm of tubular epithelial cell were dropped, that tubular epithelial cells were partially disintegrated, and that the mitochondria of tubular epithelial cells were degenerated and lost. In addition to tubular lesions, glomerular damages were also observed, including segmental foot process fusion and loss of foot process covering on glomerular basement membrane (GBM). Immunofluorescence staining indicated that the expression of nephrin and podocin were both decreased after exposure of GDF. In contrast, increased expression of desmin, a marker of podocyte injury, was found in some areas of a glomerulus. TUNEL staining showed that GDF induced apoptosis in tubular cells and glomerular cells. These studies demonstrate that GDF can induce both severe proximal tubular damage and podocyte injury in rats, and the tubular lesions appear earlier than that of glomeruli.

Mixed Organic Solvents Induce Renal Injury in Rats

PubMed Central

Qin, Weisong; Xu, Zhongxiu; Lu, Yizhou; Zeng, Caihong; Zheng, Chunxia; Wang, Shengyu; Liu, Zhihong

2012-01-01

To investigate the injury effects of organic solvents on kidney, an animal model of Sprague-Dawley (SD) rats treated with mixed organic solvents via inhalation was generated and characterized. The mixed organic solvents consisted of gasoline, dimethylbenzene and formaldehyde (GDF) in the ratio of 2∶2:1, and were used at 12,000 PPM to treat the rats twice a day, each for 3 hours. Proteinuria appeared in the rats after exposure for 5–6 weeks. The incidences of proteinuria in male and female rats after exposure for 12 weeks were 43.8% (7/16) and 25% (4/16), respectively. Urinary N-Acetyl-β-(D)-Glucosaminidase (NAG) activity was increased significantly after exposure for 4 weeks. Histological examination revealed remarkable injuries in the proximal renal tubules, including tubular epithelial cell detachment, cloud swelling and vacuole formation in the proximal tubular cells, as well as proliferation of parietal epithelium and tubular reflux in glomeruli. Ultrastructural examination found that brush border and cytoplasm of tubular epithelial cell were dropped, that tubular epithelial cells were partially disintegrated, and that the mitochondria of tubular epithelial cells were degenerated and lost. In addition to tubular lesions, glomerular damages were also observed, including segmental foot process fusion and loss of foot process covering on glomerular basement membrane (GBM). Immunofluorescence staining indicated that the expression of nephrin and podocin were both decreased after exposure of GDF. In contrast, increased expression of desmin, a marker of podocyte injury, was found in some areas of a glomerulus. TUNEL staining showed that GDF induced apoptosis in tubular cells and glomerular cells. These studies demonstrate that GDF can induce both severe proximal tubular damage and podocyte injury in rats, and the tubular lesions appear earlier than that of glomeruli. PMID:23029287

Transport characteristics of L-citrulline in renal apical membrane of proximal tubular cells.

PubMed

Mitsuoka, Keisuke; Shirasaka, Yoshiyuki; Fukushi, Akimasa; Sato, Masanobu; Nakamura, Toshimichi; Nakanishi, Takeo; Tamai, Ikumi

2009-04-01

L-Citrulline has diagnostic potential for renal function, because its plasma concentration increases with the progression of renal failure. Although L-citrulline extracted by glomerular filtration in kidney is mostly reabsorbed, the mechanism involved is not clearly understood. The present study was designed to characterize L-citrulline transport across the apical membranes of renal epithelial tubular cells, using primary-cultured rat renal proximal tubular cells, as well as the human kidney proximal tubular cell line HK-2. L-Citrulline was transported in a Na(+)-dependent manner from the apical side of both cell types cultured on permeable supports with a microporous membrane. Kinetic analysis indicated that the transport involves two distinct Na(+)-dependent saturable systems and one Na(+)-independent saturable system in HK-2 cells. The uptake was competitively inhibited by neutral and cationic, but not anionic amino acids. Relatively large cationic and anionic compounds inhibited the uptake, but smaller ones did not. In HK-2 cells, mRNA expression of SLC6A19 and SLC7A9, which encode B(0)AT1 and b(0,+)AT, respectively, was detected by RT-PCR. In addition, L-citrulline transport was significantly decreased in HK-2 cells in which either SLC6A19 or SLC7A9 was silenced. Hence, these results suggest that amino acid transporters B(0)AT1 and b(0,+)AT are involved in the reabsorption of L-citrulline in the kidney, at least in part, by mediating the apical membrane transport of L-citrulline in renal tubule cells.

Cyclic adenosine monophosphate modulates cell morphology and behavior of a cultured renal epithelial.

PubMed

Amsler, K

1990-07-01

The role of cyclic adenosine monophosphate (cAMP) dependent protein kinase (PKA) in modulating functions of differentiated renal cells is well established. Its importance in controlling their growth and differentiation is less clear. We have used somatic cell genetic techniques to probe the role of PKA in controlling morphology and behavior of a renal epithelial cell line, LLC-PK1, which acquires many properties characteristic of the renal proximal tubular cell. Mutants of this line altered in PKA activity have been isolated and their behavior compared to that of the parent line. The results indicate that PKA is involved, either directly or indirectly, in maintenance of cell morphology, cell-cell and cell-substratum interactions, density-dependent growth regulation, and expression of one function characteristic of the renal proximal tubular cell, Na-hexose symport. The relevance of these results to the role of PKA in controlling growth and differentiation of renal epithelial cells in vivo is discussed.

Pink1/Parkin-mediated mitophagy play a protective role in cisplatin induced renal tubular epithelial cells injury.

PubMed

Zhao, Chuanyan; Chen, Zhuyun; Xu, Xueqiang; An, Xiaofei; Duan, Suyan; Huang, Zhimin; Zhang, Chengning; Wu, Lin; Zhang, Bo; Zhang, Aihua; Xing, Changying; Yuan, Yanggang

2017-01-15

Cisplatin often causes acute kidney injury (AKI) in the treatment of a wide variety of malignancies. Mitochondrial dysfunction is one of the main reasons for cisplatin nephrotoxicity. Previous study showed that Pink1 and Parkin play central roles in regulating the mitophagy, which is a key protective mechanism by specifically eliminating dysfunctional or damaged mitochondria. However, the mechanisms that modulate mitophagy in cisplatin induced nephrotoxicity remain to be elucidated. The purpose of this study was to investigate the effects of Pink1/Parkin pathway in mitophagy, mitochondrial dysfunction and renal proximal tubular cells injury during cisplatin treatment. In cultured human renal proximal tubular cells, we found that knockdown of Pink1/Parkin induced the aggravation of mitochondrial function, leading to the increase of cell injury through inhibition of mitophagy. Additionally, the overexpression of Pink1/Parkin protected against cisplatin-induced mitochondrial dysfunction and cell injury by promoting mitophagy. Our results provide clear evidence that Pink1/Parkin-dependent mitophagy has identified potential targets for the treatment of cisplatin-induced AKI. Copyright © 2016 Elsevier Inc. All rights reserved.

Tenofovir Nephrotoxicity: 2011 Update

PubMed Central

Fernandez-Fernandez, Beatriz; Montoya-Ferrer, Ana; Sanz, Ana B.; Sanchez-Niño, Maria D.; Izquierdo, Maria C.; Poveda, Jonay; Sainz-Prestel, Valeria; Ortiz-Martin, Natalia; Parra-Rodriguez, Alejandro; Selgas, Rafael; Ruiz-Ortega, Marta; Egido, Jesus; Ortiz, Alberto

2011-01-01

Tenofovir is an acyclic nucleotide analogue reverse-transcriptase inhibitor structurally similar to the nephrotoxic drugs adefovir and cidofovir. Tenofovir is widely used to treat HIV infection and approved for treatment of hepatitis B virus. Despite initial cell culture and clinical trials results supporting the renal safety of tenofovir, its clinical use is associated with a low, albeit significant, risk of kidney injury. Proximal tubular cell secretion of tenofovir explains the accumulation of the drug in these mitochondria-rich cells. Tenofovir nephrotoxicity is characterized by proximal tubular cell dysfunction that may be associated with acute kidney injury or chronic kidney disease. Withdrawal of the drug leads to improvement of analytical parameters that may be partial. Understanding the risk factors for nephrotoxicity and regular monitoring of proximal tubular dysfunction and serum creatinine in high-risk patients is required to minimize nephrotoxicity. Newer, structurally similar molecular derivatives that do not accumulate in proximal tubules are under study. PMID:21716719

Clinical and molecular aspects of distal renal tubular acidosis in children.

PubMed

Besouw, Martine T P; Bienias, Marc; Walsh, Patrick; Kleta, Robert; Van't Hoff, William G; Ashton, Emma; Jenkins, Lucy; Bockenhauer, Detlef

2017-06-01

Distal renal tubular acidosis (dRTA) is characterized by hyperchloraemic metabolic acidosis, hypokalaemia, hypercalciuria and nephrocalcinosis. It is due to reduced urinary acidification by the α-intercalated cells in the collecting duct and can be caused by mutations in genes that encode subunits of the vacuolar H + -ATPase (ATP6V1B1, ATP6V0A4) or the anion exchanger 1 (SLC4A1). Treatment with alkali is the mainstay of therapy. This study is an analysis of clinical data from a long-term follow-up of 24 children with dRTA in a single centre, including a genetic analysis. Of the 24 children included in the study, genetic diagnosis was confirmed in 19 patients, with six children having mutations in ATP6V1B1, ten in ATP6V0A4 and three in SLC4A1; molecular diagnosis was not available for five children. Five novel mutations were detected (2 in ATP6V1B1 and 3 in ATP6V0A4). Two-thirds of patients presented with features of proximal tubular dysfunction leading to an erroneous diagnosis of renal Fanconi syndrome. The proximal tubulopathy disappeared after resolution of acidosis, indicating the importance of following proximal tubular function to establish the correct diagnosis. Growth retardation with a height below -2 standard deviation score was found in ten patients at presentation, but persisted in only three of these children once established on alkali treatment. Sensorineural hearing loss was found in five of the six patients with an ATP6V1B1 mutation. Only one patient with an ATP6V0A4 mutation had sensorineural hearing loss during childhood. Nine children developed medullary cysts, but without apparent clinical consequences. Cyst development in this cohort was not correlated with age at therapy onset, molecular diagnosis, growth parameters or renal function. In general, the prognosis of dRTA is good in children treated with alkali.

Compensatory Renal Hypertrophy and the Uptake of Cysteine S-Conjugates of Hg2+ in Isolated S2 Proximal Tubular Segments.

PubMed

Bridges, Christy C; Barfuss, Delon W; Joshee, Lucy; Zalups, Rudolfs K

2016-12-01

Chronic kidney disease is characterized by a progressive and permanent loss of functioning nephrons. In order to compensate for this loss, the remaining functional nephrons undergo significant structural and functional changes. We hypothesize that luminal uptake of inorganic mercury (Hg 2+ ), as a conjugate of cysteine (Cys; Cys-S-Hg-S-Cys), is enhanced in S2 segments of proximal tubules from the remnant kidney of uninephrectomized (NPX) rabbits. To test this hypothesis, we measured uptake and accumulation of Cys-S-Hg-S-Cys in isolated perfused S2 segments of proximal tubules from normal (control) and NPX rabbits. The remnant kidney in NPX rabbits undergoes significant hypertrophy during the initial 3 weeks following surgery. Tubules isolated from NPX rabbits were significantly larger in diameter and volume than those from control rabbits. Moreover, real-time PCR analyses of proximal tubules indicated that the expression of selected membrane transporters was greater in kidneys of NPX animals than in kidneys of control animals. When S2 segments from control and NPX rabbits were perfused with cystine or Cys-S-Hg-S-Cys, we found that the rates of luminal disappearance and tubular accumulation of Hg 2+  were greater in tubules from NPX animals. These increases were inhibited by the addition of various amino acids to the perfusate. Taken together, our data suggest that hypertrophic changes in proximal tubules lead to an enhanced ability of these tubules to take up and accumulate Hg 2 . © The Author 2016. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Comparison of two models for evaluation histopathology of experimental renal ischemia.

PubMed

Tirapelli, L F; Barione, D F; Trazzi, B F M; Tirapelli, D P C; Novas, P C; Silva, C S; Martinez, M; Costa, R S; Tucci, S; Suaid, H J; Cologna, A J; Martins, A C P

2009-12-01

Renal ischemia/reperfusion (I/R) injury is one of the frequent causes of acute renal failure (ARF) due to the complex, interrelated sequence of events, that result in damage to and death of kidney cells. Cells of the proximal tubular epithelium are especially susceptible to I/R injury, leading to acute tubular necrosis, which plays a pivotal role in the pathogenesis of ARF. Several models have been explicated to assess morphological changes, including those of Jabonski et al. and Goujon et al. We compared the 2 models for histopathological evaluation of 30- or 120-minute periods of renal ischemia followed by 24-hour reperfusion in rats. Several changes were observed after application of the 2 models: proximal tubular cell necrosis, loss of brush border, vacuolization, denudation of tubular basement membrane as a consequence of flattening of basal cells, and presence of intratubular exfoliated cells in the lumen of proximal convoluted tubules at various stages of degeneration (karyorexis, kariopyknosis and karyolysis). Evaluating tubular lesions after 2 periods of experimental ischemia with light microscopy allowed us to conclude that the Goujon classification better characterized the main changes in cortical renal tubules after ischemia.

Current anti-myeloma therapies in renal manifestations of monoclonal light chain-associated Fanconi syndrome: a retrospective series of 49 patients.

PubMed

Vignon, M; Javaugue, V; Alexander, M P; El-Karoui, K; Karras, A; Roos-Weil, D; Royer, B; Asli, B; Knebelmann, B; Touchard, G; Jaccard, A; Arnulf, B; Bridoux, F; Leung, N; Fermand, J P

2017-01-01

We retrospectively reviewed 49 patients with light chain (LC) Fanconi syndrome (FS). Patients presented with chronic kidney disease (median estimated glomerular filtration rate (eGFR) of 33 ml/min/1.73 m 2 ) and tubular proteinuria. All patients tested had elevated fractional excretion of phosphate, uric acid, generalized aminoaciduria and/or normoglycemic glycosuria. Thirty-eight patients had monoclonal gammopathy of renal significance and eleven patients had an overt hematological malignancy. The monoclonal LC isotype was kappa in 46/49 cases. Kidney biopsy in 39 patients showed various proximal tubular lesions and characteristic LC intracytoplasmic crystalline inclusions in 24 patients. Forty-two patients received chemotherapy. Patients with plasma cell proliferation (n=38) received bortezomib-based regimens (n=11), immunomodulatory agents (n=7) or alkylating agents (n=6). High-dose melphalan (HDM) followed by autologous stem cell transplantation was performed in 14 patients. Hematological response was obtained in 90% of evaluable patients, assessed on serum free light chains (FLC). GFR remained stable as long as hematological response was maintained and declined when serum FLC level rebounded. Improvement in proximal tubule function occurred in 13 patients. In patients with LC-associated FS, chemotherapy using HDM and/or new generation anti-myeloma agents can stabilize renal function and improve proximal tubule function. Serum FLC should be used to assess the hematological response, related to renal outcome.

A Role for Tubular Necroptosis in Cisplatin-Induced AKI

PubMed Central

Xu, Yanfang; Ma, Huabin; Shao, Jing; Wu, Jianfeng; Zhou, Linying; Zhang, Zhirong; Wang, Yuze; Huang, Zhe; Ren, Junming; Liu, Suhuan; Chen, Xiangmei

2015-01-01

Cell death and inflammation in the proximal tubules are the hallmarks of cisplatin-induced AKI, but the mechanisms underlying these effects have not been fully elucidated. Here, we investigated whether necroptosis, a type of programmed necrosis, has a role in cisplatin-induced AKI. We found that inhibition of any of the core components of the necroptotic pathway—receptor-interacting protein 1 (RIP1), RIP3, or mixed lineage kinase domain-like protein (MLKL)—by gene knockout or a chemical inhibitor diminished cisplatin-induced proximal tubule damage in mice. Similar results were obtained in cultured proximal tubular cells. Furthermore, necroptosis of cultured cells could be induced by cisplatin or by a combination of cytokines (TNF-α, TNF-related weak inducer of apoptosis, and IFN-γ) that were upregulated in proximal tubules of cisplatin-treated mice. However, cisplatin induced an increase in RIP1 and RIP3 expression in cultured tubular cells in the absence of cytokine release. Correspondingly, overexpression of RIP1 or RIP3 enhanced cisplatin-induced necroptosis in vitro. Notably, inflammatory cytokine upregulation in cisplatin-treated mice was partially diminished in RIP3- or MLKL-deficient mice, suggesting a positive feedback loop involving these genes and inflammatory cytokines that promotes necroptosis progression. Thus, our data demonstrate that necroptosis is a major mechanism of proximal tubular cell death in cisplatin-induced nephrotoxic AKI. PMID:25788533

The association between vitamin B12, albuminuria and reduced kidney function: an observational cohort study

USDA-ARS?s Scientific Manuscript database

Background: Variants in CUBN, the gene encoding cubilin, a proximal tubular transport protein, have been associated with albuminuria and vitamin B12 (B12) deficiency. We hypothesized that low levels of B12 would be associated with albuminuria in a population-based cohort. Methods: We analyzed parti...

Aging and the Disposition and Toxicity of Mercury in Rats

PubMed Central

Bridges, Christy C.; Joshee, Lucy; Zalups, Rudolfs K.

2014-01-01

Progressive loss of functioning nephrons, secondary to age-related glomerular disease, can impair the ability of the kidneys to effectively clear metabolic wastes and toxicants from blood. Additionally, as renal mass is diminished, cellular hypertrophy occurs in functional nephrons that remain. We hypothesize that these nephrons are exposed to greater levels of nephrotoxicants, such as inorganic mercury (Hg2+), and thus are at an increased risk of becoming intoxicated by these compounds. The purpose of the present study was to characterize the effects of aging on the disposition and renal toxicity of Hg2+ in young adult and aged Wistar rats. Paired groups of animals were injected (i.v.) with either a 0.5 μmol • kg−1 non-nephrotoxic or a 2.5 μmol • kg−1 nephrotoxic dose of mercuric chloride (HgCl2). Plasma creatinine and renal biomarkers of proximal tubular injury were greater in both groups of aged rats than in the corresponding groups of young adult rats. Histologically, evidence of glomerular sclerosis, tubular atrophy, interstitial inflammation and fibrosis were significant features of kidneys from aged animals. In addition, proximal tubular necrosis, especially along the straight segments in the inner cortex and outer stripe of the outer medulla was a prominent feature in the renal sections from both aged and young rats treated with the nephrotoxic dose of HgCl2. Our findings indicate 1) that overall renal function is significantly impaired in aged rats, resulting in chronic renal insufficiency and 2) the disposition of HgCl2 in aging rats is significantly altered compared to that of young rats. PMID:24548775

Fascin-1 is released from proximal tubular cells in response to calcineurin inhibitors (CNIs) and correlates with isometric vacuolization in kidney transplanted patients

PubMed Central

Jacobs-Cachá, Conxita; Torres, Irina B; López-Hellín, Joan; Cantarell, Carme; Azancot, María A; Román, Antonio; Moreso, Francesc; Serón, Daniel; Meseguer, Anna; Sarró, Eduard

2017-01-01

Immunosuppression based on calcineurin inhibitors (CNIs) has greatly improved organ transplantation, although subsequent nephrotoxicity significantly hinders treatment success. There are no currently available specific soluble biomarkers for CNI-induced nephrotoxicity and diagnosis relies on renal biopsy, which is costly, invasive and may cause complications. Accordingly, identification of non-invasive biomarkers distinguishing CNI-induced kidney tubular damage from that of other etiologies would greatly improve diagnosis and enable more precise dosage adjustment. For this purpose, HK-2 cells, widely used to model human proximal tubule, were treated with CNIs cyclosporine-A and FK506, or staurosporine as a calcineurin-independent toxic compound, and secretomes of each treatment were analyzed by proteomic means. Among the differentially secreted proteins identified, only fascin-1 was specifically released by both CNIs but not by staurosporine. To validate fascin-1 as a biomarker of CNI-induced tubular toxicity, fascin-1 levels were analyzed in serum and urine from kidney-transplanted patients under CNIs treatment presenting or not isometric vacuolization (IV), which nowadays represents the main histological hallmark of CNI-induced tubular damage. Patients with chronic kidney disease (CKD) and healthy volunteers were used as controls. Our results show that urinary fascin-1 was only significantly elevated in the subset of CNI-treated patients presenting IV. Moreover, fascin-1 anticipated the rise of sCr levels in serially collected urine samples from CNI-treated pulmonary-transplanted patients, where a decline in kidney function and serum creatinine (sCr) elevation was mainly attributed to CNIs treatment. In conclusion, our results point towards fascin-1 as a putative soluble biomarker of CNI-induced damage in the kidney tubular compartment. PMID:28979691

Fascin-1 is released from proximal tubular cells in response to calcineurin inhibitors (CNIs) and correlates with isometric vacuolization in kidney transplanted patients.

PubMed

Jacobs-Cachá, Conxita; Torres, Irina B; López-Hellín, Joan; Cantarell, Carme; Azancot, María A; Román, Antonio; Moreso, Francesc; Serón, Daniel; Meseguer, Anna; Sarró, Eduard

2017-01-01

Immunosuppression based on calcineurin inhibitors (CNIs) has greatly improved organ transplantation, although subsequent nephrotoxicity significantly hinders treatment success. There are no currently available specific soluble biomarkers for CNI-induced nephrotoxicity and diagnosis relies on renal biopsy, which is costly, invasive and may cause complications. Accordingly, identification of non-invasive biomarkers distinguishing CNI-induced kidney tubular damage from that of other etiologies would greatly improve diagnosis and enable more precise dosage adjustment. For this purpose, HK-2 cells, widely used to model human proximal tubule, were treated with CNIs cyclosporine-A and FK506, or staurosporine as a calcineurin-independent toxic compound, and secretomes of each treatment were analyzed by proteomic means. Among the differentially secreted proteins identified, only fascin-1 was specifically released by both CNIs but not by staurosporine. To validate fascin-1 as a biomarker of CNI-induced tubular toxicity, fascin-1 levels were analyzed in serum and urine from kidney-transplanted patients under CNIs treatment presenting or not isometric vacuolization (IV), which nowadays represents the main histological hallmark of CNI-induced tubular damage. Patients with chronic kidney disease (CKD) and healthy volunteers were used as controls. Our results show that urinary fascin-1 was only significantly elevated in the subset of CNI-treated patients presenting IV. Moreover, fascin-1 anticipated the rise of sCr levels in serially collected urine samples from CNI-treated pulmonary-transplanted patients, where a decline in kidney function and serum creatinine (sCr) elevation was mainly attributed to CNIs treatment. In conclusion, our results point towards fascin-1 as a putative soluble biomarker of CNI-induced damage in the kidney tubular compartment.

Cytochrome P450 and Lipoxygenase Metabolites on Renal Function

PubMed Central

Imig, John D.; Hye Khan, Md. Abdul

2018-01-01

Arachidonic acid metabolites have a myriad of biological actions including effects on the kidney to alter renal hemodynamics and tubular transport processes. Cyclooxygenase metabolites are products of an arachidonic acid enzymatic pathway that has been extensively studied in regards to renal function. Two lesser-known enzymatic pathways of arachidonic acid metabolism are the lipoxygenase (LO) and cytochrome P450 (CYP) pathways. The importance of LO and CYP metabolites to renal hemodynamics and tubular transport processes is now being recognized. LO and CYP metabolites have actions to alter renal blood flow and glomerular filtration rate. Proximal and distal tubular sodium transport and fluid and electrolyte homeostasis are also significantly influenced by renal CYP and LO levels. Metabolites of the LO and CYP pathways also have renal actions that influence renal inflammation, proliferation, and apoptotic processes at vascular and epithelial cells. These renal LO and CYP pathway actions occur through generation of specific metabolites and cell-signaling mechanisms. Even though the renal physiological importance and actions for LO and CYP metabolites are readily apparent, major gaps remain in our understanding of these lipid mediators to renal function. Future studies will be needed to fill these major gaps regarding LO and CYP metabolites on renal function. PMID:26756638

Role of NF-κB in oxidative stress-induced defective dopamine D1 receptor signaling in the renal proximal tubules of Sprague Dawley rats

PubMed Central

Fardoun, Riham Zein; Asghar, Mohammad; Lokhandwala, Mustafa

2009-01-01

Dopamine promotes sodium excretion, in part, via activation of D1 receptors in renal proximal tubules (PT) and subsequent inhibition of Na, K-ATPase. Recently, we have reported that oxidative stress causes D1 receptors-G-protein uncoupling via mechanisms involving Protein Kinase C (PKC) and G-protein Coupled Receptor Kinase 2 (GRK2) in the primary culture of renal PT of Sprague Dawley (SD) rats. There are reports suggesting that redox-sensitive nuclear transcription factor, NF-κB, is activated in conditions associated with oxidative stress. This study was designed to identify the role of NF-κB in oxidative stress–induced defective renal D1 receptor –G-protein coupling and function. Treatment of the PT with hydrogen peroxide (H2O2, 50 μM/20 min) induced the nuclear translocation of NF-κB, increased PKC activity, and triggered the translocation of GRK2 to the proximal tubular membranes. This was accompanied by hyperphosphorylation of D1 receptors and defective D1 receptor-G-protein coupling. The functional consequence of these changes was decreased D1 receptor activation-mediated inhibition of Na, K-ATPase activity. Interestingly, pre-treatment with pyrrolidine dithiocarbamate (PDTC, 25 μM/10min), an NF-κB inhibitor, blocked the H2O2-induced nuclear translocation of NF-κB, increase in PKC activity, as well as GRK2 translocation and hyperphosphorylation of D1 receptors in the proximal tubular membranes. Furthermore, PDTC restored D1 receptor G-protein coupling and D1 receptor agonist-mediated inhibition of the Na, KATPase activity. Therefore, we suggest that oxidative stress causes nuclear translocation of NF-κB in the renal proximal tubules, which contributes to defective D1-receptor-G-protein coupling and function via mechanism involving PKC, membranous translocation of GRK 2, and subsequent phosphorylation of dopamine D1 receptors. PMID:17320758

Proximal renal tubular injury in rats sub-chronically exposed to low fluoride concentrations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cárdenas-González, Mariana C.; Del Razo, Luz M.; Barrera-Chimal, Jonatan

2013-11-01

Fluoride is usually found in groundwater at a very wide range of concentration between 0.5 and 25 ppm. At present, few studies have assessed the renal effects of fluoride at environmentally relevant concentrations. Furthermore, most of these studies have used insensitive and nonspecific biomarkers of kidney injury. The aim of this study was to use early and sensitive biomarkers to evaluate kidney injury after fluoride exposure to environmentally relevant concentrations. Recently weaned male Wistar rats were exposed to low (15 ppm) and high (50 ppm) fluoride concentrations in drinking water for a period of 40 days. At the end ofmore » the exposure period, kidney injury biomarkers were measured in urine and renal mRNA expression levels were assessed by real time RT-PCR. Our results showed that the urinary kidney injury molecule (Kim-1), clusterin (Clu), osteopontin (OPN) and heat shock protein 72 excretion rate significantly increased in the group exposed to the high fluoride concentration. Accordingly, fluoride exposure increased renal Kim-1, Clu and OPN mRNA expression levels. Moreover, there was a significant dose-dependent increase in urinary β-2-microglobulin and cystatin-C excretion rate. Additionally, a tendency towards a dose dependent increase of tubular damage in the histopathological light microscopy findings confirmed the preferential impact of fluoride on the tubular structure. All of these changes occurred at early stages in which, the renal function was not altered. In conclusion using early and sensitive biomarkers of kidney injury, we were able to found proximal tubular alterations in rats sub-chronically exposed to fluoride. - Highlights: • Exposure to low concentrations of fluoride induced proximal tubular injury • Increase in urinary Kim-1, Clu, OPN and Hsp72 in 50 ppm fluoride-exposed group • Increase in urinary B2M and CysC in 15 and 50 ppm fluoride-exposed groups • Fluoride exposure increased renal Kim, Clu and OPN mRNA expression levels. • Fluoride increased kidney injury biomarkers at stages where eGFR was unaltered.« less

Multiphoton imaging for assessing renal disposition in acute kidney injury

NASA Astrophysics Data System (ADS)

Liu, Xin; Liang, Xiaowen; Wang, Haolu; Roberts, Darren M.; Roberts, Michael S.

2016-11-01

Estimation of renal function and drug renal disposition in acute kidney injury (AKI), is important for appropriate dosing of drugs and adjustment of therapeutic strategies, but is challenging due to fluctuations in kidney function. Multiphoton microscopy has been shown to be a useful tool in studying drug disposition in liver and can reflect dynamic changes of liver function. We extend this imaging technique to investigate glomerular filtration rate (GFR) and tubular transporter functional change in various animal models of AKI, which mimic a broad range of causes of AKI such as hypoxia (renal ischemia- reperfusion), therapeutic drugs (e.g. cisplatin), rhabdomyolysis (e.g. glycerol-induced) and sepsis (e.g. LPSinduced). The MPM images revealed acute injury of tubular cells as indicated by reduced autofluorescence and cellular vacuolation in AKI groups compared to control group. In control animal, systemically injected FITC-labelled inulin was rapidly cleared from glomerulus, while the clearance of FITC-inulin was significantly delayed in most of animals in AKI group, which may reflect the reduced GFR in AKI. Following intravenous injection, rhodamine 123, a fluorescent substrate of p-glycoprotein (one of tubular transporter), was excreted into urine in proximal tubule via p-glycoprotein; in response to AKI, rhodamine 123 was retained in tubular cells as revealed by slower decay of fluorescence intensity, indicating P-gp transporter dysfunction in AKI. Thus, real-time changes in GFR and transporter function can be imaged in rodent kidney with AKI using multiphoton excitation of exogenously injected fluorescent markers.

Altered renal sodium handling and risk of incident hypertension: Results of the Olivetti Heart Study

PubMed Central

D’Elia, Lanfranco; Cappuccio, Francesco P.; Iacone, Roberto; Russo, Ornella; Galletti, Ferruccio; Strazzullo, Pasquale

2017-01-01

Renal tubular sodium (Na) handling plays a key role in blood pressure (BP) regulation. Several cross-sectional studies reported a positive association between higher proximal tubule fractional reabsorption of Na and BP, but no prospective investigation has been reported of this possible association. Hence, the purpose of this study was to estimate the predictive role of renal Na handling on the risk of incident hypertension and the changes in BP occurring in the 8-year follow-up observation of a sample of initially normotensive men (The Olivetti Heart Study). The study included 294 untreated normotensive non-diabetic men with normal renal function examined twice (1994–95 and 2002–04). Renal tubular Na handling was estimated by exogenous lithium clearance. Fractional reabsorption of Na in proximal and distal tubules was calculated and included in the analysis. At baseline, there was no association between BP and either proximal or distal fractional reabsorption of Na. At the end of the 8-year follow-up, direct associations were observed between baseline proximal (but not distal) Na fractional reabsorption and the changes occurred in systolic and diastolic BP over time (+2.79 and +1.53 mmHg, respectively, per 1SD difference in proximal Na-FR; p<0.01). Also multivariable analysis showed a direct association between baseline proximal Na fractional reabsorption and risk of incident hypertension, independently of potential confounders (OR: 1.34, 95%CI:1.06–1.70). The results of this prospective investigation strongly suggest a causal relationship between an enhanced rate of Na reabsorption in the proximal tubule and the risk of incident hypertension in initially normotensive men. PMID:28196131

Overexpressed cyclophilin B suppresses aldosterone-induced proximal tubular cell injury both in vitro and in vivo.

PubMed

Wang, Bin; Lin, Lilu; Wang, Haidong; Guo, Honglei; Gu, Yong; Ding, Wei

2016-10-25

The renin-angiotensin-aldosterone system (RAAS) is overactivated in patients with chronic kidney disease. Oxidative stress and endoplasmic reticulum stress (ERS) are two major mechanisms responsible for aldosterone-induced kidney injury. Cyclophilin (CYP) B is a chaperone protein that accelerates the rate of protein folding through its peptidyl-prolyl cis-trans isomerase (PPIase) activity. We report that overexpression of wild-type CYPB attenuated aldosterone-induced oxidative stress (evidenced by reduced production of reactive oxygen species and improved mitochondrial dysfunction), ERS (indicated by reduced expression of the ERS markers glucose-regulated protein 78 [GRP78] and C/-EBP homologous protein [CHOP]), and tubular cell apoptosis in comparison with aldosterone-induced human kidney-2 (HK-2) cells. The in vivo study also yielded similar results. Hence, CYPB performs a crucial function in protecting cells against aldosterone-induced oxidative stress, ERS, and tubular cell injury via its PPIase activity.

Overexpressed cyclophilin B suppresses aldosterone-induced proximal tubular cell injury both in vitro and in vivo

PubMed Central

Wang, Haidong; Guo, Honglei; Gu, Yong; Ding, Wei

2016-01-01

The renin-angiotensin-aldosterone system (RAAS) is overactivated in patients with chronic kidney disease. Oxidative stress and endoplasmic reticulum stress (ERS) are two major mechanisms responsible for aldosterone-induced kidney injury. Cyclophilin (CYP) B is a chaperone protein that accelerates the rate of protein folding through its peptidyl-prolyl cis-trans isomerase (PPIase) activity. We report that overexpression of wild-type CYPB attenuated aldosterone-induced oxidative stress (evidenced by reduced production of reactive oxygen species and improved mitochondrial dysfunction), ERS (indicated by reduced expression of the ERS markers glucose-regulated protein 78 [GRP78] and C/-EBP homologous protein [CHOP]), and tubular cell apoptosis in comparison with aldosterone-induced human kidney-2 (HK-2) cells. The in vivo study also yielded similar results. Hence, CYPB performs a crucial function in protecting cells against aldosterone-induced oxidative stress, ERS, and tubular cell injury via its PPIase activity. PMID:27732567

A case of Fanconi syndrome due to a deferasirox overdose and a trial of plasmapheresis.

PubMed

Shah, L; Powell, J L; Zaritsky, J J

2017-10-01

Deferasirox has nephrotoxic effects in the context of chronic therapy. This case report illustrates proximal tubular dysfunction (Fanconi syndrome) due to an acute deferasirox overdose. In response, we trialled plasmapheresis to eliminate the drug. Deferasirox levels were obtained in the context of three rounds of plasmapheresis. Given the half-life model of decay, we concluded that plasmapheresis may not have been successful. The patient ultimately recovered normal tubular function after 2 months. This report is the first to describe acute deferasirox-induced nephrotoxicity, and the application of plasmapheresis that, ultimately, did not change the typical time to recovery. © 2017 John Wiley & Sons Ltd.

Micropuncture studies of the recovery phase of myohemoglobinuric acute renal failure in the rat

PubMed Central

Oken, Donald E.; DiBona, Gerald F.; McDonald, Franklin D.

1970-01-01

Micropuncture studies of the recovery phase of glycerol-induced myohemoglobinuric acute renal failure were performed in rats whose blood urea nitrogen (BUN) had fallen at least 20% below its peak value. The glomerular filtration rate (GFR) of individual nephrons in a single kidney in the recovery period generally either was in the normal range or minimal. Each animal's BUN concentration at the time of the study was inversely related to the proportion of functioning surface nephrons, but did not correlate with individual nephron GFR values. Proximal tubule fractional water absorption was significantly depressed as manifested by both depressed inulin (TF/P) values and supernormal volumes of collections, a finding which, in the absence of a urea-induced osmotic diuresis, suggests impaired sodium transport by the damaged nephron. The mean proximal tubule hydrostatic pressure in recovery was normal and there was little variation in pressure among functioning nephrons. It is concluded that recovery from this model of acute renal failure reflects the progressive recruitment of increasing numbers of functioning nephrons. The recovery of individual nephron glomerular filtration, once begun, was rapid and complete. No evidence could be adduced that the gradual return of renal function towards normal reflects a slow release of tubular obstruction or repair of disrupted tubular epithelium. Rather, recovery appeared to be directly attributable to the return of an adequate effective glomerular filtration pressure. Significant limitation in proximal tubule water absorption persisted after individual nephron GFR had returned to normal or supernormal values in this model of experimental acute renal failure in the rat, a finding which readily accounts for the diuresis associated with the recovery phase of this syndrome. PMID:5443173

Normal tubular regeneration and differentiation of the post-ischemic kidney in mice lacking vimentin.

PubMed Central

Terzi, F.; Maunoury, R.; Colucci-Guyon, E.; Babinet, C.; Federici, P.; Briand, P.; Friedlander, G.

1997-01-01

Proliferation and dedifferentiation of tubular cells are the hallmark of early regeneration after renal ischemic injury. Vimentin, a class III intermediate filament expressed only in mesenchymal cells of mature mammals, was shown to be transiently expressed in post-ischemic renal tubular epithelial cells. Vimentin re-expression was interpreted as a marker of cellular dedifferentiation, but its role in tubular regeneration after renal ischemia has also been hypothesized. This role was evaluated in mice bearing a null mutation of the vimentin gene. Expression of vimentin, proliferating cell nuclear antigen (a marker of cellular proliferation), and villin (a marker of differentiated brush-border membranes) was studied in wild-type (Vim+/+), heterozygous (Vim+/-), and homozygous (Vim-/-) mice subjected to transient ischemia of the left kidney. As expected, vimentin was detected by immunohistochemistry at the basal pole of proximal tubular cells from post-ischemic kidney in Vim+/+ and Vim+/- mice from day 2 to day 28. The expression of the reporter gene beta-galactosidase in Vim+/- and Vim-/- mice confirmed the tubular origin of vimentin. No compensatory expression of keratin could be demonstrated in Vim-/- mice. The intensity of proliferating cell nuclear antigen labeling and the pattern of villin expression were comparable in Vim-/-, Vim+/- and Vim+/+ mice at any time of the study. After 60 days, the structure of post-ischemic kidneys in Vim-/- mice was indistinguishable from that of normal non-operated kidneys in Vim+/+ mice. In conclusion, 1) the pattern of post-ischemic proximal tubular cell proliferation, differentiation, and tubular organization was not impaired in mice lacking vimentin and 2) these results suggest that the transient tubular expression of vimentin is not instrumental in tubular regeneration after renal ischemic injury. Images Figure 1 Figure 2 Figure 3 Figure 5 Figure 6 Figure 7 PMID:9094992

External Genital Development, Urethra Formation, and Hypospadias Induction in Guinea Pig: A Double Zipper Model for Human Urethral Development.

PubMed

Wang, Shanshan; Shi, Mingxin; Zhu, Dongqing; Mathews, Ranjiv; Zheng, Zhengui

2018-03-01

To determine whether the guinea pig phallus would be an appropriate model of human penile development, we characterized the embryology and sexual differentiation of guinea pig external genitalia and attended to induce hypospadias in males and tubular urethra formation in females pharmacologically. The external genitalia of guinea pig were collected from genital swelling initiation to newborn stages, and scanning electronic microscopy and histology were performed to visualize the morphology and structure. Immunohistochemistry was used to determine the androgen receptor localization. Bicalutamide and methyltestosterone were given to pregnant dams to reveal the role and timing of androgen in guinea pig penile masculinization. Canalization and dorsal-to-ventral movement of the urethral canal develops the urethral groove in both sexes, and then the males perform distal-opening-proximal-closing to form tubular urethra. More nuclear-localized androgen receptor is found in proximal genital tubercles of males than in females at (E) 29. Antiandrogen treatment at E26-E30 can cause hypospadias, and methyltestosterone administration at E27-E31 can induce tubular urethra formation in females. Fetal development of the guinea pig phallus is homologous to that of humans. Although guinea pig has structures similar to mouse, the urethral groove and the tubular urethra formation are more similar to humans. Antiandrogen treatment causes hypospadias in males and additional androgen induces tubular urethra formation in females. Thus, guinea pig is an appropriate model for further study of cellular and molecular mechanisms involved in distal-opening-proximal-closing in tubular urethra formation and the evaluation of the pathophysiological processes of hypospadias. Published by Elsevier Inc.

A micropuncture study of the effect of parathyroid hormone on renal bicarbonate reabsorption.

PubMed Central

Bank, N; Aynediian, H S

1976-01-01

Renal micropuncture and clearance experiments were carried out in rats to study the effect of parathyroid hormone (PTH) on renal tubular HCO-/3 reabsorption. The rats were studied during an initial period of parathyroid deficiency (acute thyroidparathyroidectomy, TPTX) and during infusion of large amounts of bovine PTH. Under normal acid-base conditions, PTH administration to TPTX rats caused a significant rise in proximal tubular fluid HCO-/3 concentration (TFHCO-/3), a decrease in fluid reabsorption, and a fall in proximal HCO-/3 reabsorption from 94.0 to 88.2% (P less than 0.01). In control experiments with mannitol infusion, a comparable reduction in proximal fluid reabsorption occurred without any significant effect on intraluminal HCO-/3 concentration. During acute intravenous HCO-/3 loading, PTH inhibited proximal HCO-/3 reabsorption. However, no change in whole kidney HCO-/3 reabsorption was observed in these experiments or in the animals studied under normal acid-base conditions. The findings are consistent with the view that PTH inhibits proximal tubular HCO-/3 reabsorption with normal or high filtered loads of HCO-/3, but distal segments of the nephron are able to reabsorb the excess delivered from the proximal tubule. Measurements of urinary ammonium and titratable acid indicate that net acid excretion (NH+/4 + TA -- HCO-/3) increases significantly after PTH administration. These results do not provide support for the view that PTH excess causes metabolic acidosis by reducing renal acid excretion. PMID:956369

Nephropathy associated with sickle cell anemia: an autologous immune complex nephritis. I. Studies on nature of glomerular-bound antibody and antigen identification in a patient with sickle cell disease and immune deposit glomerulonephritis.

PubMed

Strauss, J; Pardo, V; Koss, M N; Griswold, W; McIntosh, R M

1975-03-01

The nature of the glomerular-bound antibody and the putative antigen was investigated in one of the patients with sickle cell disease and immune deposit membranoproliferative glomerulonephritis by immunohistologic and glomerular antibody elution. Renal proximal tubular epithelial antigen was localized in association with immunoglobulins G (IgG), M (IgM), Clq fraction of the first component of complement (Clq) and the third component of complement (C3) in a granular pattern along the glomerular basement membrane of the patient's kidney. IgG and IgM were eluted from glomeruli. These immunoglobulins fixed to the proximal tubules of normal human kidney by direct immunofluorescence. This localization was abolished by absorption of the eluted immunoglobulins with renal tubular epithelial (RTE) antigen. The IgG eluted from the glomeruli blocked the fixation of rabbit anti-RTE antigen to normal proximal tubular brush border. These studies suggest that the nephritis in this patient was due to deposition of complexes or RTE antigen and specific antibody. An autologous immune complex nephritis may develop in some patients with sickle cell anemia secondary to RTE antigen released possibly after renal ischemia or some other phenomenon causing renal tubular damage.

Hypertrophy of proximal tubular epithelial cells induced by low pH in vitro is independent of ammoniagenesis.

PubMed

Bevington, A; Millwater, C J; Walls, J

1994-01-01

Metabolic acidosis can lead to tubular hypertrophy in vivo. This is thought to arise from stimulation of renal production of ammonia, a known hypertrophic agent. To examine this effect in vitro, confluent opossum (OK) proximal tubular epithelial cells were cultured at acidic pH (7.21 +/- 0.02) or at control pH (7.37 +/- 0.01) for 4 days. Protein content was 9% higher at acidic pH whereas DNA content was unaffected. The resulting increase in mean cell size (protein/DNA ratio) was 10% but correlated inversely with the mass of cells in control wells, varying from +48% at low cell mass to -14% at high cell mass. In contrast, low pH decreased 3H-thymidine incorporation by 9%. However, ammonia production was unaffected. These changes in protein/DNA ratio and 3H-thymidine incorporation cannot therefore be attributed to acid-induced ammoniagenesis and imply that low pH exerts a more direct effect on tubular cell growth than previously envisaged.

Response of human renal tubular cells to cyclosporine and sirolimus: A toxicogenomic study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pallet, Nicolas; Rabant, Marion; Xu-Dubois, Yi-Chun

The molecular mechanisms involved in the potentially nephrotoxic response of tubular cells to immunosuppressive drugs remain poorly understood. Transcriptional profiles of human proximal tubular cells exposed to cyclosporine A (CsA), sirolimus (SRL) or their combination, were established using oligonucleotide microarrays. Hierarchical clustering of genes implicated in fibrotic processes showed a clear distinction between expression profiles with CsA and CsA + SRL treatments on the one hand and SRL treatment on the other. Functional analysis found that CsA and CsA + SRL treatments preferentially alter biological processes located at the cell membrane, such as ion transport or signal transduction, whereas SRLmore » modifies biological processes within the nucleus and related to transcriptional activity. Genome wide expression analysis suggested that CsA may induce an endoplasmic reticulum (ER) stress in tubular cells in vitro. Moreover we found that CsA exposure in vivo is associated with the upregulation of the ER stress marker BIP in kidney transplant biopsies. In conclusion, this toxicogenomic study highlights the molecular interaction networks that may contribute to the tubular response to CsA and SRL. These results may also offer a new working hypothesis for future research in the field of CsA nephrotoxicity. Further studies are needed to evaluate if ER stress detection in tubular cells in human biopsies can predict CsA nephrotoxicity.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van der Hauwaert, Cynthia; Savary, Grégoire; Buob, David

Numerous xenobiotics have been shown to be harmful for the kidney. Thus, to improve our knowledge of the cellular processing of these nephrotoxic compounds, we evaluated, by real-time PCR, the mRNA expression level of 377 genes encoding xenobiotic-metabolizing enzymes (XMEs), transporters, as well as nuclear receptors and transcription factors that coordinate their expression in eight normal human renal cortical tissues. Additionally, since several renal in vitro models are commonly used in pharmacological and toxicological studies, we investigated their metabolic capacities and compared them with those of renal tissues. The same set of genes was thus investigated in HEK293 and HK2more » immortalized cell lines in commercial primary cultures of epithelial renal cells and in proximal tubular cell primary cultures. Altogether, our data offers a comprehensive description of kidney ability to process xenobiotics. Moreover, by hierarchical clustering, we observed large variations in gene expression profiles between renal cell lines and renal tissues. Primary cultures of proximal tubular epithelial cells exhibited the highest similarities with renal tissue in terms of transcript profiling. Moreover, compared to other renal cell models, Tacrolimus dose dependent toxic effects were lower in proximal tubular cell primary cultures that display the highest metabolism and disposition capacity. Therefore, primary cultures appear to be the most relevant in vitro model for investigating the metabolism and bioactivation of nephrotoxic compounds and for toxicological and pharmacological studies. - Highlights: • Renal proximal tubular (PT) cells are highly sensitive to xenobiotics. • Expression of genes involved in xenobiotic disposition was measured. • PT cells exhibited the highest similarities with renal tissue.« less

Nephrolithiasis in renal tubular acidosis.

PubMed

Buckalew, V M

1989-03-01

Renal tubular acidosis is a term applied to several conditions in which metabolic acidosis is caused by specific defects in renal tubular hydrogen ion secretion. Three types of renal tubular acidosis generally are recognized based on the nature of the tubular defect. Nephrolithiasis occurs only in type I renal tubular acidosis, a condition marked by an abnormality in the generation and maintenance of a hydrogen ion gradient by the distal tubule. A forme fruste of type I renal tubular acidosis has been described in which the characteristic defect in distal hydrogen ion secretion occurs in the absence of metabolic acidosis (incomplete renal tubular acidosis). Type I renal tubular acidosis is a heterogeneous disorder that may be hereditary, idiopathic or secondary to a variety of conditions. Secondary type I renal tubular acidosis in sporadic cases is associated most commonly with autoimmune diseases, such as Sjögren's syndrome and systemic lupus erythematosus, and it occurs more frequently in women than men. Nephrolithiasis, which may occur in any of the subsets of type I renal tubular acidosis, accounts for most of the morbidity in adults and adolescents. Major risk factors for nephrolithiasis include alkaline urine, hypercalciuria and hypocitraturia. In addition, we found hyperuricosuria in 21 per cent of the patients with type I renal tubular acidosis with nephrolithiasis. The most frequently occurring risk factor, hypocitraturia, is due to decreased filtered load and/or to increased tubular reabsorption of filtered citrate. While increased tubular reabsorption may be due to systemic acidosis, hypocitraturia occurs in incomplete renal tubular acidosis. Furthermore, alkali therapy (either bicarbonate or citrate salts) increases citrate excretion in complete and incomplete type I renal tubular acidosis. These data suggest that hypocitraturia in type I renal tubular acidosis may be due to a defect in proximal tubule function. Hypercalciuria appears to have 2 causes. It may be due to metabolic acidosis, usually in children with a hereditary defect in urine acidification. In other cases familial idiopathic hypercalciuria causes nephrocalcinosis and nephrolithiasis resulting in distal tubular damage and type I renal tubular acidosis. In these latter cases hypercalciuria is present in complete and incomplete type I renal tubular acidosis. Potassium citrate appears to reduce calcium excretion in both types of hypercalciuric type I renal tubular acidosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Phosphorylation of Stats at Ser727 in renal proximal tubular epithelial cells exposed to cadmium.

PubMed

Nakagawa, Junko; Nishitai, Gen; Inageda, Kiyoshi; Matsuoka, Masato

2007-11-01

The effects of cadmium exposure on serine phosphorylation of signal transducers and activators of transcription (Stats) and an upstream kinase were examined in renal proximal tubular cells. In porcine LLC-PK1 cells treated with cadmium, Stat1 and Stat3 proteins were phosphorylated at Ser727 without changing total Stat protein levels. While phosphorylated forms of the members of mitogen-activated protein kinases (MAPKs) increased in response to cadmium exposure, treatment with a p38 inhibitor, SB203580 reduced Ser727 phosphorylation of Stat1 and Stat3 markedly in LLC-PK1 cells. The expression of human matrix metalloproteinase-3 (MMP-3), a Stats-inducible gene, was found to be up-regulated in human HK-2 cells exposed to cadmium, and suppressed by preincubation with SB203580. These results suggest that cadmium might induce the phosphorylation of Stat1 and Stat3 at Ser727 via the p38 pathway at least in part, and modulate gene expression in these proximal tubular cells. Copyright © 2007 Elsevier B.V. All rights reserved.

CYTOCHROME P450-DEPENDENT METABOLISM OF TRICHLOROETHYLENE IN THE RAT KIDNEY

EPA Science Inventory

The metabolism of trichloroethylene (Tri) by cytochrome P450 (P450) was studied in microsomes from liver and kidney homogenates and from isolated renal proximal tubular (PT) and distal tubular (DT) cells from male Fischer 344 rats. Chloral hydrate (CH) was the only metabolite con...

Bioprinting of 3D Convoluted Renal Proximal Tubules on Perfusable Chips

NASA Astrophysics Data System (ADS)

Homan, Kimberly A.; Kolesky, David B.; Skylar-Scott, Mark A.; Herrmann, Jessica; Obuobi, Humphrey; Moisan, Annie; Lewis, Jennifer A.

2016-10-01

Three-dimensional models of kidney tissue that recapitulate human responses are needed for drug screening, disease modeling, and, ultimately, kidney organ engineering. Here, we report a bioprinting method for creating 3D human renal proximal tubules in vitro that are fully embedded within an extracellular matrix and housed in perfusable tissue chips, allowing them to be maintained for greater than two months. Their convoluted tubular architecture is circumscribed by proximal tubule epithelial cells and actively perfused through the open lumen. These engineered 3D proximal tubules on chip exhibit significantly enhanced epithelial morphology and functional properties relative to the same cells grown on 2D controls with or without perfusion. Upon introducing the nephrotoxin, Cyclosporine A, the epithelial barrier is disrupted in a dose-dependent manner. Our bioprinting method provides a new route for programmably fabricating advanced human kidney tissue models on demand.

Bioprinting of 3D Convoluted Renal Proximal Tubules on Perfusable Chips

PubMed Central

Homan, Kimberly A.; Kolesky, David B.; Skylar-Scott, Mark A.; Herrmann, Jessica; Obuobi, Humphrey; Moisan, Annie; Lewis, Jennifer A.

2016-01-01

Three-dimensional models of kidney tissue that recapitulate human responses are needed for drug screening, disease modeling, and, ultimately, kidney organ engineering. Here, we report a bioprinting method for creating 3D human renal proximal tubules in vitro that are fully embedded within an extracellular matrix and housed in perfusable tissue chips, allowing them to be maintained for greater than two months. Their convoluted tubular architecture is circumscribed by proximal tubule epithelial cells and actively perfused through the open lumen. These engineered 3D proximal tubules on chip exhibit significantly enhanced epithelial morphology and functional properties relative to the same cells grown on 2D controls with or without perfusion. Upon introducing the nephrotoxin, Cyclosporine A, the epithelial barrier is disrupted in a dose-dependent manner. Our bioprinting method provides a new route for programmably fabricating advanced human kidney tissue models on demand. PMID:27725720

OCRL controls trafficking through early endosomes via PtdIns4,5P2-dependent regulation of endosomal actin

PubMed Central

Vicinanza, Mariella; Di Campli, Antonella; Polishchuk, Elena; Santoro, Michele; Di Tullio, Giuseppe; Godi, Anna; Levtchenko, Elena; De Leo, Maria Giovanna; Polishchuk, Roman; Sandoval, Lisette; Marzolo, Maria-Paz; De Matteis, Maria Antonietta

2011-01-01

Mutations in the phosphatidylinositol 4,5-bisphosphate (PtdIns4,5P2) 5-phosphatase OCRL cause Lowe syndrome, which is characterised by congenital cataracts, central hypotonia, and renal proximal tubular dysfunction. Previous studies have shown that OCRL interacts with components of the endosomal machinery; however, its role in endocytosis, and thus the pathogenic mechanisms of Lowe syndrome, have remained elusive. Here, we show that via its 5-phosphatase activity, OCRL controls early endosome (EE) function. OCRL depletion impairs the recycling of multiple classes of receptors, including megalin (which mediates protein reabsorption in the kidney) that are retained in engorged EEs. These trafficking defects are caused by ectopic accumulation of PtdIns4,5P2 in EEs, which in turn induces an N-WASP-dependent increase in endosomal F-actin. Our data provide a molecular explanation for renal proximal tubular dysfunction in Lowe syndrome and highlight that tight control of PtdIns4,5P2 and F-actin at the EEs is essential for exporting cargoes that transit this compartment. PMID:21971085

Functional characterization of apical transporters expressed in rat proximal tubular cells (PTCs) in primary culture.

PubMed

Nakanishi, Takeo; Fukushi, Akimasa; Sato, Masanobu; Yoshifuji, Mayuko; Gose, Tomoka; Shirasaka, Yoshiyuki; Ohe, Kazuyo; Kobayashi, Masato; Kawai, Keiichi; Tamai, Ikumi

2011-12-05

Since in vitro cell culture models often show altered apical transporter expression, they are not necessarily suitable for the analysis of renal transport processes. Therefore, we aimed here to investigate the usefulness of primary-cultured rat proximal tubular cells (PTCs) for this purpose. After isolation of renal cortical cells from rat kidneys, PTCs were enriched and the gene expression and function of apical transporters were analyzed by means of microarray, RT-PCR and uptake experiments. RT-PCR confirmed that the major apical transporters were expressed in rat PTCs. Na(+)-dependent uptake of α-methyl-d-glucopyranoside (αMG), ergothioneine and carnitine by the PTCs suggests functional expression of Sglts, Octn1 and Octn2, respectively. Inhibition of pH-dependent glycylsarcosine uptake by low concentration of cephalexin, which is a β-lactam antibiotics recognized by Pepts, indicates a predominant role of high affinity type Pept2, but not low affinity type Pept1, in the PTCs. Moreover, the permeability ratio of [(14)C]αMG (apical to basolateral/basolateral to apical) across PTCs was 4.3, suggesting that Sglt-mediated reabsorptive transport is characterized. In conclusion, our results indicate that rat PTCs in primary culture are found to be a promising in vitro model to evaluate reabsorption processes mediated at least by Sglts, Pept2, Octn1 and Octn2.

HIF-1-mediated production of exosomes during hypoxia is protective in renal tubular cells.

PubMed

Zhang, Wei; Zhou, Xiangjun; Yao, Qisheng; Liu, Yutao; Zhang, Hao; Dong, Zheng

2017-10-01

Exosomes are nano-sized vesicles produced and secreted by cells to mediate intercellular communication. The production and function of exosomes in kidney tissues and cells remain largely unclear. Hypoxia is a common pathophysiological condition in kidneys. This study was designed to characterize exosome production during hypoxia of rat renal proximal tubular cells (RPTCs), investigate the regulation by hypoxia-inducible factor-1 (HIF-1), and determine the effect of the exosomes on ATP-depletion-induced tubular cell injury. Hypoxia did not change the average sizes of exosomes secreted by RPTCs, but it significantly increased exosome production in a time-dependent manner. HIF-1 induction with dimethyloxalylglycine also promoted exosome secretion, whereas pharmacological and genetic suppression of HIF-1 abrogated the increase of exosome secretion under hypoxia. The exosomes from hypoxic RPTCs had inhibitory effects on apoptosis of RPTCs following ATP depletion. The protective effects were lost in the exosomes from HIF-1α knockdown cells. It is concluded that hypoxia stimulates exosome production and secretion in renal tubular cells. The exosomes from hypoxic cells are protective against renal tubular cell injury. HIF-1 mediates exosome production during hypoxia and contributes to the cytoprotective effect of the exosomes. Copyright © 2017 the American Physiological Society.

Thioredoxin interacting protein (TXNIP) regulates tubular autophagy and mitophagy in diabetic nephropathy through the mTOR signaling pathway

PubMed Central

Huang, Chunling; Zhang, Yuan; Kelly, Darren J.; Tan, Christina Y. R.; Gill, Anthony; Cheng, Delfine; Braet, Filip; Park, Jin-Sung; Sue, Carolyn M.; Pollock, Carol A.; Chen, Xin-Ming

2016-01-01

Hyperglycemia upregulates thioredoxin interacting protein (TXNIP) expression, which in turn induces ROS production, inflammatory and fibrotic responses in the diabetic kidney. Dysregulation of autophagy contributes to the development of diabetic nephropathy. However, the interaction of TXNIP with autophagy/mitophagy in diabetic nephropathy is unknown. In this study, streptozotocin-induced diabetic rats were given TXNIP DNAzyme or scrambled DNAzyme for 12 weeks respectively. Fibrotic markers, mitochondrial function and mitochondrial reactive oxygen species (mtROS) were assessed in kidneys. Tubular autophagy and mitophagy were determined in kidneys from both human and rats with diabetic nephropathy. TXNIP and autophagic signaling molecules were examined. TXNIP DNAzyme dramatically attenuated extracellular matrix deposition in the diabetic kidneys compared to the control DNAzyme. Accumulation of autophagosomes and reduced autophagic clearance were shown in tubular cells of human diabetic compared to non-diabetic kidneys, which was reversed by TXNIP DNAzyme. High glucose induced mitochondrial dysfunction and mtROS production, and inhibited mitophagy in proximal tubular cells, which was reversed by TXNIP siRNA. TXNIP inhibition suppressed diabetes-induced BNIP3 expression and activation of the mTOR signaling pathway. Collectively, hyperglycemia-induced TXNIP contributes to the dysregulation of tubular autophagy and mitophagy in diabetic nephropathy through activation of the mTOR signaling pathway. PMID:27381856

Cross talk between primary human renal tubular cells and endothelial cells in cocultures.

PubMed

Tasnim, Farah; Zink, Daniele

2012-04-15

Interactions between renal tubular epithelial cells and adjacent endothelial cells are essential for normal renal functions but also play important roles in renal disease and repair. Here, we investigated cocultures of human primary renal proximal tubular cells (HPTC) and human primary endothelial cells to address the cross talk between these cell types. HPTC showed improved proliferation, marker gene expression, and enzyme activity in cocultures. Also, the long-term maintenance of epithelia formed by HPTC was improved, which was due to the secretion of transforming growth factor-β1 and its antagonist α2-macroglobulin. HPTC induced endothelial cells to secrete increased amounts of these factors, which balanced each other functionally and only displayed in combination the observed positive effects. In addition, in the presence of HPTC endothelial cells expressed increased amounts of hepatocyte growth factor and vascular endothelial growth factor, which have well-characterized effects on renal tubular epithelial cells as well as on endothelial cells. Together, the results showed that HPTC stimulated endothelial cells to express a functionally balanced combination of various factors, which in turn improved the performance of HPTC. The results give new insights into the cross talk between renal epithelial and endothelial cells and suggest that cocultures could be also useful models for the analysis of cellular communication in renal disease and repair. Furthermore, the characterization of defined microenvironments, which positively affect HPTC, will be helpful for improving the performance of this cell type in in vitro applications including in vitro toxicology and kidney tissue engineering.

Chronic unilateral ureteral obstruction in the neonatal mouse delays maturation of both kidneys and leads to late formation of atubular glomeruli

PubMed Central

Forbes, Michael S.; Thornhill, Barbara A.; Galarreta, Carolina I.; Minor, Jordan J.; Gordon, Katherine A.

2013-01-01

Unilateral ureteral obstruction (UUO) in the adult mouse is the most widely used model of progressive renal disease: the proximal tubule is the nephron segment most severely affected and atubular glomeruli are formed after only 7 days of UUO. To determine the proximal nephron response to UUO in the maturing kidney, neonatal mice were examined 7 to 28 days following complete UUO under general anesthesia. Proximal tubular mass and maturation were determined by staining with Lotus tetragolonobus lectin. Superoxide was localized by nitroblue tetrazolium and collagen by Sirius red. Cell proliferation, cell death, PAX-2, megalin, α-smooth muscle actin (α-SMA), renin, and fibronectin were identified by immunohistochemistry. During the first 14 days of ipsilateral UUO, despite oxidative stress (4-hydroxynonenal staining), glomerulotubular continuity was maintained and mitochondrial superoxide production persisted. However, from 14 to 28 days, papillary growth was impaired and proximal tubules collapsed with increased apoptosis, autophagy, mitochondrial loss, and formation of atubular glomeruli. Fibronectin, α-SMA, and collagen increased in the obstructed kidney. Oxidative stress was present also in the contralateral kidney: renin was decreased, glomerulotubular maturation and papillary growth were delayed, followed by increased cortical and medullary growth. We conclude that neonatal UUO initially delays renal maturation and results in oxidative stress in both kidneys. In contrast to the adult, proximal tubular injury in the neonatal obstructed kidney is delayed at 14 days, followed only later by the formation of atubular glomeruli. Antioxidant therapies directed at proximal tubular mitochondria during early renal maturation may slow progression of congenital obstructive nephropathy. PMID:24107422

Berberine activates Nrf2 nuclear translocation and inhibits apoptosis induced by high glucose in renal tubular epithelial cells through a phosphatidylinositol 3-kinase/Akt-dependent mechanism.

PubMed

Zhang, Xiuli; Liang, Dan; Lian, Xu; Jiang, Yan; He, Hui; Liang, Wei; Zhao, Yue; Chi, Zhi-Hong

2016-06-01

Apoptosis of tubular epithelial cells is a major feature of diabetic kidney disease, and hyperglycemia triggers the generation of free radicals and oxidant stress in tubular cells. Berberine (BBR) is identified as a potential anti-diabetic herbal medicine due to its beneficial effects on insulin sensitivity, glucose metabolism and glycolysis. In this study, the underlying mechanisms involved in the protective effects of BBR on high glucose-induced apoptosis were explored using cultured renal tubular epithelial cells (NRK-52E cells) and human kidney proximal tubular cell line (HK-2 cells). We identified the pivotal role of phosphatidylinositol 3-kinase (PI3K)/Akt in BBR cellular defense mechanisms and revealed the novel effect of BBR on nuclear factor (erythroid-derived 2)-related factor-2 (Nrf2) and heme oxygenase (HO)-1 in NRK-52E and HK-2 cells. BBR attenuated reactive oxygen species production, antioxidant defense (GSH and SOD) and oxidant-sensitive proteins (Nrf2 and HO-1), which also were blocked by LY294002 (an inhibitor of PI3K) in HG-treated NRK-52E and HK-2 cells. Furthermore, BBR improved mitochondrial function by increasing mitochondrial membrane potential. BBR-induced anti-apoptotic function was demonstrated by decreasing apoptotic proteins (cytochrome c, Bax, caspase3 and caspase9). All these findings suggest that BBR exerts the anti-apoptosis effects through activation of PI3K/Akt signal pathways and leads to activation of Nrf2 and induction of Nrf2 target genes, and consequently protecting the renal tubular epithelial cells from HG-induced apoptosis.

Total protein, albumin and low-molecular-weight protein excretion in HIV-positive patients.

PubMed

Campbell, Lucy J; Dew, Tracy; Salota, Rashim; Cheserem, Emily; Hamzah, Lisa; Ibrahim, Fowzia; Sarafidis, Pantelis A; Moniz, Caje F; Hendry, Bruce M; Poulton, Mary; Sherwood, Roy A; Post, Frank A

2012-08-10

Chronic kidney disease is common in HIV positive patients and renal tubular dysfunction has been reported in those receiving combination antiretroviral therapy (cART). Tenofovir (TFV) in particular has been linked to severe renal tubular disease as well as proximal tubular dysfunction. Markedly elevated urinary concentrations of retinal-binding protein (RBP) have been reported in patients with severe renal tubular disease, and low-molecular-weight proteins (LMWP) such as RBP may be useful in clinical practice to assess renal tubular function in patients receiving TFV. We analysed 3 LMWP as well as protein and albumin in the urine of a sample of HIV positive patients. In a cross-sectional fashion, total protein, albumin, RBP, cystatin C, and neutrophil gelatinase-associated lipocalin (NGAL) were quantified in random urine samples of 317 HIV positive outpatients and expressed as the ratio-to-creatinine (RBPCR, CCR and NGALCR). Exposure to cART was categorised as none, cART without TFV, and cART containing TFV and a non-nucleoside reverse-transcriptase-inhibitor (TFV/NNRTI) or TFV and a protease-inhibitor (TFV/PI). Proteinuria was present in 10.4 % and microalbuminuria in 16.7 % of patients. Albumin accounted for approximately 10 % of total urinary protein. RBPCR was within the reference range in 95 % of patients while NGALCR was elevated in 67 % of patients. No overall differences in urine protein, albumin, and LMWP levels were observed among patients stratified by cART exposure, although a greater proportion of patients exposed to TFV/PI had RBPCR >38.8 μg/mmol (343 μg/g) (p = 0.003). In multivariate analyses, black ethnicity (OR 0.43, 95 % CI 0.24, 0.77) and eGFR <75 mL/min/1.73 m2 (OR 3.54, 95 % CI 1.61, 7.80) were independently associated with upper quartile (UQ) RBPCR. RBPCR correlated well to CCR (r2 = 0.71), but not to NGALCR, PCR or ACR. In HIV positive patients, proteinuria was predominantly of tubular origin and microalbuminuria was common. RBPCR in patients without overt renal tubular disease was generally within the reference range, including those receiving TFV. RBP therefore appears a promising biomarker for monitoring renal tubular function in patients receiving TFV and for distinguishing patients with normal tubular function or mild tubular dysfunction from those with severe renal tubular disease or Fanconi syndrome.

Chaperone-Mediated Autophagy in the Kidney: The Road More Traveled

PubMed Central

Franch, Harold A.

2014-01-01

Summary Chaperone-mediated autophagy (CMA) is a lysosomal proteolytic pathway in which cytosolic substrate proteins contain specific chaperone recognition sequences required for degradation and are translocated directly across the lysosomal membrane for destruction. CMA proteolytic activity has a reciprocal relationship with macroautophagy: CMA is most active in cells in which macroautophagy is least active. Normal renal proximal tubular cells have low levels of macroautophagy, but high basal levels of CMA activity. CMA activity is regulated by starvation, growth factors, oxidative stress, lipids, aging, and retinoic acid signaling. The physiological consequences of changes in CMA activity depend on the substrate proteins present in a given cell type. In the proximal tubule, increased CMA results from protein or calorie starvation and from oxidative stress. Overactivity of CMA can be associated with tubular lysosomal pathology and certain cancers. Reduced CMA activity contributes to protein accumulation in renal tubular hypertrophy, but may contribute to oxidative tissue damage in diabetes and aging. Although there are more questions than answers about the role of high basal CMA activity, this remarkable feature of tubular protein metabolism appears to influence a variety of chronic diseases. PMID:24485032

Distinct Requirements for Vacuolar Protein Sorting 34 Downstream Effector Phosphatidylinositol 3-Phosphate 5-Kinase in Podocytes Versus Proximal Tubular Cells

PubMed Central

Venkatareddy, Madhusudan; Verma, Rakesh; Kalinowski, Anne; Patel, Sanjeevkumar R.; Shisheva, Assia

2016-01-01

The mechanisms by which the glomerular filtration barrier prevents the loss of large macromolecules and simultaneously, maintains the filter remain poorly understood. Recent studies proposed that podocytes have an active role in both the endocytosis of filtered macromolecules and the maintenance of the filtration barrier. Deletion of a key endosomal trafficking regulator, the class 3 phosphatidylinositol (PtdIns) 3-kinase vacuolar protein sorting 34 (Vps34), in podocytes results in aberrant endosomal membrane morphology and podocyte dysfunction. We recently showed that the vacuolation phenotype in cultured Vps34–deficient podocytes is caused by the absence of a substrate for the Vps34 downstream effector PtdIns 3-phosphate 5-kinase (PIKfyve), which phosphorylates Vps34-generated PtdIns(3)P to produce PtdIns (3,5)P2. PIKfyve perturbation and PtdIns(3,5)P2 reduction result in massive membrane vacuolation along the endosomal system, but the cell-specific functions of PIKfyve in vivo remain unclear. We show here that the genetic deletion of PIKfyve in endocytically active proximal tubular cells resulted in the development of large cytoplasmic vacuoles caused by arrested endocytic traffic progression at a late-endosome stage. In contrast, deletion of PIKfyve in glomerular podocytes did not significantly alter the endosomal morphology, even in age 18-month-old mice. However, on culturing, the PIKfyve-deleted podocytes developed massive cytoplasmic vacuoles. In summary, these data suggest that glomerular podocytes and proximal tubules have different requirements for PIKfyve function, likely related to distinct in vivo needs for endocytic flux. PMID:26825532

Nifedipine inhibits advanced glycation end products (AGEs) and their receptor (RAGE) interaction-mediated proximal tubular cell injury via peroxisome proliferator-activated receptor-gamma activation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsui, Takanori; Yamagishi, Sho-ichi, E-mail: shoichi@med.kurume-u.ac.jp; Takeuchi, Masayoshi

2010-07-23

Research highlights: {yields} Nifedipine inhibited the AGE-induced up-regulation of RAGE mRNA levels in tubular cells, which was prevented by GW9662, an inhibitor of peroxisome proliferator-activated receptor-{gamma}. {yields} GW9662 treatment alone increased RAGE mRNA levels in tubular cells. {yields} Nifedipine inhibited the AGE-induced reactive oxygen species generation, NF-{kappa}B activation and increases in intercellular adhesion molecule-1 and transforming growth factor-{beta} gene expression in tubular cells, all of which were blocked by GW9662. -- Abstract: There is a growing body of evidence that advanced glycation end products (AGEs) and their receptor (RAGE) interaction evokes oxidative stress generation and subsequently elicits inflammatory and fibrogenicmore » reactions, thereby contributing to the development and progression of diabetic nephropathy. We have previously found that nifedipine, a calcium-channel blocker (CCB), inhibits the AGE-induced mesangial cell damage in vitro. However, effects of nifedipine on proximal tubular cell injury remain unknown. We examined here whether and how nifedipine blocked the AGE-induced tubular cell damage. Nifedipine, but not amlodipine, a control CCB, inhibited the AGE-induced up-regulation of RAGE mRNA levels in tubular cells, which was prevented by the simultaneous treatment of GW9662, an inhibitor of peroxisome proliferator-activated receptor-{gamma} (PPAR{gamma}). GW9662 treatment alone was found to increase RAGE mRNA levels in tubular cells. Further, nifedipine inhibited the AGE-induced reactive oxygen species generation, NF-{kappa}B activation and increases in intercellular adhesion molecule-1 and transforming growth factor-beta gene expression in tubular cells, all of which were blocked by GW9662. Our present study provides a unique beneficial aspect of nifedipine on diabetic nephropathy; it could work as an anti-oxidative and anti-inflammatory agent against AGEs in tubular cells by suppressing RAGE expression via PPAR{gamma} activation.« less

P1,P4-diadenosine tetraphosphate (Ap4A) inhibits proximal tubular reabsorption of sodium in rats.

PubMed

Stiepanow-Trzeciak, Anna; Jankowski, Maciej; Angielski, Stefan; Szczepanska-Konkel, Miroslawa

2007-01-01

P1,P4-diadenosine tetraphosphate (Ap4A) is a vasoactive dinucleotide possessing natriuretic activity. It is unclear, however, which part of the nephron is the target site of action for Ap4A. We evaluated the tubular sites of Ap4A action using the lithium clearance technique. Ap4A at a priming dose of 2 micromol/kg with subsequent infusion at 20 nmol/kg/min increased fractional water and sodium excretion 2.5- and 5.6-fold, respectively. Moreover, Ap4A increased lithium clearance 1.9-fold and fractional lithium excretion 2.8-fold. Fractional water and sodium excretion from distal nephron segments was not significantly affected by Ap4A. These results suggest that Ap4A induces natriuresis mainly through inhibition of proximal tubular reabsorption of sodium. Copyright 2007 S. Karger AG, Basel.

The kidney in vitamin B12 and folate homeostasis: characterization of receptors for tubular uptake of vitamins and carrier proteins.

PubMed

Birn, Henrik

2006-07-01

Over the past 10 years, animal studies have uncovered the molecular mechanisms for the renal tubular recovery of filtered vitamin and vitamin carrier proteins. Relatively few endocytic receptors are responsible for the proximal tubule uptake of a number of different vitamins, preventing urinary losses. In addition to vitamin conservation, tubular uptake by endocytosis is important to vitamin metabolism and homeostasis. The present review focuses on the receptors involved in renal tubular recovery of folate, vitamin B12, and their carrier proteins. The multiligand receptor megalin is important for the uptake and tubular accumulation of vitamin B12. During vitamin load, the kidney accumulates large amounts of free vitamin B12, suggesting a possible storage function. In addition, vitamin B12 is metabolized in the kidney, suggesting a role in vitamin homeostasis. The folate receptor is important for the conservation of folate, mediating endocytosis of the vitamin. Interaction between the structurally closely related, soluble folate-binding protein and megalin suggests that megalin plays an additional role in the uptake of folate bound to filtered folate-binding protein. A third endocytic receptor, the intrinsic factor-B12 receptor cubilin-amnionless complex, is essential to the renal tubular uptake of albumin, a carrier of folate. In conclusion, uptake is mediated by interaction with specific endocytic receptors also involved in the renal uptake of other vitamins and vitamin carriers. Little is known about the mechanisms regulating intracellular transport and release of vitamins, and whereas tubular uptake is a constitutive process, this may be regulated, e.g., by vitamin status.

Proximal Tubular Cannabinoid-1 Receptor Regulates Obesity-Induced CKD.

PubMed

Udi, Shiran; Hinden, Liad; Earley, Brian; Drori, Adi; Reuveni, Noa; Hadar, Rivka; Cinar, Resat; Nemirovski, Alina; Tam, Joseph

2017-12-01

Obesity-related structural and functional changes in the kidney develop early in the course of obesity and occur independently of hypertension, diabetes, and dyslipidemia. Activating the renal cannabinoid-1 receptor (CB 1 R) induces nephropathy, whereas CB 1 R blockade improves kidney function. Whether these effects are mediated via a specific cell type within the kidney remains unknown. Here, we show that specific deletion of CB 1 R in the renal proximal tubule cells did not protect the mice from obesity, but markedly attenuated the obesity-induced lipid accumulation in the kidney and renal dysfunction, injury, inflammation, and fibrosis. These effects associated with increased activation of liver kinase B1 and the energy sensor AMP-activated protein kinase, as well as enhanced fatty acid β -oxidation. Collectively, these findings indicate that renal proximal tubule cell CB 1 R contributes to the pathogenesis of obesity-induced renal lipotoxicity and nephropathy by regulating the liver kinase B1/AMP-activated protein kinase signaling pathway. Copyright © 2017 by the American Society of Nephrology.

Cellular distribution of cell cycle-related molecules in the renal tubules of rats treated with renal carcinogens for 28 days: relationship between cell cycle aberration and carcinogenesis.

PubMed

Taniai, Eriko; Hayashi, Hitomi; Yafune, Atsunori; Watanabe, Maiko; Akane, Hirotoshi; Suzuki, Kazuhiko; Mitsumori, Kunitoshi; Shibutani, Makoto

2012-09-01

Some renal carcinogens can induce karyomegaly, which reflects aberrant cell division in the renal tubules, from the early stages of exposure. To clarify the cell cycle-related changes during the early stages of renal carcinogenesis, we performed immunohistochemical analysis of tubular cells in male F344 rats treated with carcinogenic doses of representative renal carcinogens for 28 days. For this purpose, the karyomegaly-inducing carcinogens ochratoxin A (OTA), ferric nitrilotriacetic acid, and monuron, and the non-karyomegaly-inducing carcinogens tris(2-chloroethyl) phosphate and potassium bromate were examined. For comparison, a karyomegaly-inducing non-carcinogen, p-nitrobenzoic acid, and a non-carcinogenic non-karyomegaly-inducing renal toxicant, acetaminophen, were also examined. The outer stripe of the outer medulla (OSOM) and the cortex + OSOM were subjected to morphometric analysis of immunoreactive proximal tubular cells. Renal carcinogens, irrespective of their karyomegaly-inducing potential, increased proximal tubular cell proliferation accompanied by an increase in topoisomerase IIα-immunoreactive cells, suggesting a reflection of cell proliferation. Karyomegaly-inducing carcinogens increased nuclear Cdc2-, γH2AX-, and phosphorylated Chk2-immunoreactive cells in both areas, the former two acting in response to DNA damage and the latter one suggestive of sustained G₂. OTA, an OSOM-targeting carcinogen, could easily be distinguished from untreated controls and non-carcinogens by evaluation of molecules responding to DNA damage and G₂/M transition in the OSOM. Thus, all renal carcinogens examined facilitated proximal tubular proliferation by repeated short-term treatment. Among these, karyomegaly-inducing carcinogens may cause DNA damage and G₂ arrest in the target tubular cells.

Dietary sodium induces a redistribution of the tubular metabolic workload

PubMed Central

Udwan, Khalil; Abed, Ahmed; Roth, Isabelle; Dizin, Eva; Maillard, Marc; Bettoni, Carla; Loffing, Johannes; Wagner, Carsten A.; Edwards, Aurélie

2017-01-01

Key points Body Na+ content is tightly controlled by regulated urinary Na+ excretion.The intrarenal mechanisms mediating adaptation to variations in dietary Na+ intake are incompletely characterized.We confirmed and expanded observations in mice that variations in dietary Na+ intake do not alter the glomerular filtration rate but alter the total and cell‐surface expression of major Na+ transporters all along the kidney tubule.Low dietary Na+ intake increased Na+ reabsorption in the proximal tubule and decreased it in more distal kidney tubule segments.High dietary Na+ intake decreased Na+ reabsorption in the proximal tubule and increased it in distal segments with lower energetic efficiency.The abundance of apical transporters and Na+ delivery are the main determinants of Na+ reabsorption along the kidney tubule.Tubular O2 consumption and the efficiency of sodium reabsorption are dependent on sodium diet. Abstract Na+ excretion by the kidney varies according to dietary Na+ intake. We undertook a systematic study of the effects of dietary salt intake on glomerular filtration rate (GFR) and tubular Na+ reabsorption. We examined the renal adaptive response in mice subjected to 7 days of a low sodium diet (LSD) containing 0.01% Na+, a normal sodium diet (NSD) containing 0.18% Na+ and a moderately high sodium diet (HSD) containing 1.25% Na+. As expected, LSD did not alter measured GFR and increased the abundance of total and cell‐surface NHE3, NKCC2, NCC, α‐ENaC and cleaved γ‐ENaC compared to NSD. Mathematical modelling predicted that tubular Na+ reabsorption increased in the proximal tubule but decreased in the distal nephron because of diminished Na+ delivery. This prediction was confirmed by the natriuretic response to diuretics targeting the thick ascending limb, the distal convoluted tubule or the collecting system. On the other hand, HSD did not alter measured GFR but decreased the abundance of the aforementioned transporters compared to NSD. Mathematical modelling predicted that tubular Na+ reabsorption decreased in the proximal tubule but increased in distal segments with lower transport efficiency with respect to O2 consumption. This prediction was confirmed by the natriuretic response to diuretics. The activity of the metabolic sensor adenosine monophosphate‐activated protein kinase (AMPK) was related to the changes in tubular Na+ reabsorption. Our data show that fractional Na+ reabsorption is distributed differently according to dietary Na+ intake and induces changes in tubular O2 consumption and sodium transport efficiency. PMID:28940314

A microperfusion study of sucrose movement across the rat proximal tubule during renal vein constriction

PubMed Central

Bank, Norman; Yarger, William E.; Aynedjian, Hagop S.

1971-01-01

Constriction of the renal vein has been shown to inhibit net sodium and water reabsorption by the rat proximal tubule. The mechanism is unknown but might be the result of inhibition of the active sodium pump induced by changes in the interstitial fluid compartment of the kidney, or to enhanced passive backflux of sodium and water into the cell or directly into the tubular lumen. Since passive movement of solutes across epithelial membranes is determined in part by the permeability characteristics of the epithelium, an increase in the permeability of the proximal tubule during venous constriction would suggest that enhanced passive flux is involved in the inhibition of reabsorption. In the present experiments, isolated segments of rat proximal convoluted tubules were microperfused in vivo with saline while the animals were receiving 14C-labeled sucrose intravenously. In normal control animals, no sucrose was detected in the majority of the collected tubular perfusates. In rats with renal vein constriction (RVC), however, sucrose consistently appeared in the tubular perfusates. The rate of inflow of sucrose correlated with the length of the perfused segment, estimated by fractional water reabsorption. In another group of animals with renal vein constriction, inulin-14C was given intravenously and the proximal tubules similarly microperfused. Inulin did not appear in the majority of collected perfusates in these animals. These observations indicate that a physiological alteration in the permeability of the proximal tubule occurs during RVC. Such an increase in permeability is consistent with the view that enhanced passive extracellular back-flux plays a role in the reduction of net sodium and water reabsorption in this experimental condition. PMID:5540167

[Clonal association of flat epithelial atypia and tubular breast cancer].

PubMed

Aulmann, S; Elsawaf, Z; Penzel, R; Schirmacher, P; Sinn, H P

2008-11-01

Flat epithelial atypia (FEA) of the breast has recently gained attention as a possible precursor lesion of highly differentiated breast cancer. Especially tubular carcinomas, with which FEA shares cytological features, often occur in close proximity to each other. To examine a possible clonal relationship, we analysed mutations of the highly variable region of the mitochondrial genome in a series of tubular carcinomas, associated FEA and normal glands. Multiple sequence alignment showed identical mtDNA mutations in approximately 50% of paired FEA and tumour samples, indicative of a clonal relationship. Our data indicate a possible precursor role of FEA in the development of tubular breast cancer.

Diabetes and renal tubular cell apoptosis

PubMed Central

Habib, Samy L

2013-01-01

Apoptosis contributes to the development of diabetic nephropathy, but the mechanism by which high glucose induces apoptosis is not fully understood. Apoptosis of tubular epithelial cells is a major feature of diabetic kidney disease, and hyperglycemia triggers the generation of free radicals and oxidant stress in tubular cells. Hyperglycemia and high glucose in vitro also lead to apoptosis, a form of programmed cell death. High glucose similar to those seen with hyperglycemia in people with diabetes mellitus, lead to accelerated apoptosis, a form of programmed cell death characterized by cell shrinkage, chromatin condensation and DNA fragmentation, in variety of cell types, including renal proximal tubular epithelial cells. PMID:23593533

Diabetes and renal tubular cell apoptosis.

PubMed

Habib, Samy L

2013-04-15

Apoptosis contributes to the development of diabetic nephropathy, but the mechanism by which high glucose induces apoptosis is not fully understood. Apoptosis of tubular epithelial cells is a major feature of diabetic kidney disease, and hyperglycemia triggers the generation of free radicals and oxidant stress in tubular cells. Hyperglycemia and high glucose in vitro also lead to apoptosis, a form of programmed cell death. High glucose similar to those seen with hyperglycemia in people with diabetes mellitus, lead to accelerated apoptosis, a form of programmed cell death characterized by cell shrinkage, chromatin condensation and DNA fragmentation, in variety of cell types, including renal proximal tubular epithelial cells.

Toxicological significance of renal Bcrp: Another potential transporter in the elimination of mercuric ions from proximal tubular cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bridges, Christy C., E-mail: bridges_cc@mercer.edu; Zalups, Rudolfs K.; Joshee, Lucy

Secretion of inorganic mercury (Hg{sup 2+}) from proximal tubular cells into the tubular lumen has been shown to involve the multidrug resistance-associated protein 2 (Mrp2). Considering similarities in localization and substrate specificity between Mrp2 and the breast cancer resistance protein (Bcrp), we hypothesize that Bcrp may also play a role in the proximal tubular secretion of mercuric species. In order to test this hypothesis, the uptake of Hg{sup 2+} was examined initially using inside-out membrane vesicles containing Bcrp. The results of these studies suggest that Bcrp may be capable of transporting certain conjugates of Hg{sup 2+}. To further characterize themore » role of Bcrp in the handling of mercuric ions and in the induction of Hg{sup 2+}-induced nephropathy, Sprague–Dawley and Bcrp knockout (bcrp{sup −/−}) rats were exposed intravenously to a non-nephrotoxic (0.5 μmol·kg{sup −1}), a moderately nephrotoxic (1.5 μmol·kg{sup −1}) or a significantly nephrotoxic (2.0 μmol·kg{sup −1}) dose of HgCl{sub 2}. In general, the accumulation of Hg{sup 2+} was greater in organs of bcrp{sup −/−} rats than in Sprague–Dawley rats, suggesting that Bcrp may play a role in the export of Hg{sup 2+} from target cells. Within the kidney, cellular injury and necrosis was more severe in bcrp{sup −/−} rats than in controls. The pattern of necrosis, which was localized in the inner cortex and the outer stripe of the outer medulla, was significantly different from that observed in Mrp2-deficient animals. These findings suggest that Bcrp may be involved in the cellular export of select mercuric species and that its role in this export may differ from that of Mrp2. - Highlights: • Bcrp may mediate transport of mercury out of proximal tubular cells. • Hg-induced nephropathy was more severe in Bcrp knockout rats. • Bcrp and Mrp2 may differ in their ability to transport Hg.« less

Puerarin protects against lead-induced cytotoxicity in cultured primary rat proximal tubular cells.

PubMed

Liu, Gang; Li, Zifa; Wang, Jinqiu; Wang, Hong; Wang, Zhenyong; Wang, Lin

2014-10-01

Puerarin, a potent free radicals scavenger, has been demonstrated to have protective efficacy in oxidative damage induced by nephrotoxins. In the present study, the attenuating effect of puerarin (PU) on lead (Pb)-induced apoptosis and oxidative stress was investigated in cultured primary rat proximal tubular (rPT) cells. Results showed that exposure to 0.5 µM Pb induced a decrease in cell viability accompanied with obvious cellular morphological alterations and caused an increase in apoptotic rate and apoptotic morphological changes. Simultaneously, depletion of mitochondrial membrane potential (ΔΨ) and intracellular glutathione (GSH); elevation of caspase-3 activity, intracellular reactive oxygen species, and malondialdehyde levels; and inhibition of GSH peroxidase (GSH-Px) activity were revealed in the cells exposed to Pb alone. However, simultaneous supplementation with PU (50 and 100 µM) protected rPT cells from Pb-induced cytotoxicity through inhibiting apoptosis, attenuating lipid peroxidation, renewing mitochondrial function, and elevating the intracellular antioxidants (nonenzymatic and enzymic) levels. In conclusion, these findings suggested that PU, as a widely distributed dietary antioxidant, contributes potentially to inhibition of Pb-induced cytotoxicity in rPT cells. © The Author(s) 2014.

Trehalose protects against cadmium-induced cytotoxicity in primary rat proximal tubular cells via inhibiting apoptosis and restoring autophagic flux

PubMed Central

Wang, Xin-Yu; Yang, Heng; Wang, Min-Ge; Yang, Du-Bao; Wang, Zhen-Yong; Wang, Lin

2017-01-01

Autophagy has an important renoprotective function and we recently found that autophagy inhibition is involved in cadmium (Cd)-induced nephrotoxicity. Here, we aimed to investigate the protective effect of trehalose (Tre), a novel autophagy activator, against Cd-induced cytotoxicity in primary rat proximal tubular (rPT) cells. First, data showed that Tre treatment significantly decreased Cd-induced apoptotic cell death of rPT cells via inhibiting caspase-dependent apoptotic pathway, evidenced by morphological analysis, flow cytometric and immunoblot assays. Also, administration with Tre protected rPT cells against Cd-induced lipid peroxidation. Inhibition of autophagic flux in Cd-exposed rPT cells was markedly restored by Tre administration, demonstrated by immunoblot analysis of autophagy marker proteins and GFP and RFP tandemly tagged LC3 method. Resultantly, Cd-induced autophagosome accumulation was obviously alleviated by Tre treatment. Meanwhile, blockage of autophagosome–lysosome fusion by Cd exposure was noticeably restored by Tre, which promoted the autophagic degradation in Cd-exposed rPT cells. Moreover, Tre treatment markedly recovered Cd-induced lysosomal alkalinization and impairment of lysosomal degradation capacity in rPT cells, demonstrating that Tre has the ability to restore Cd-impaired lysosomal function. Collectively, these findings demonstrate that Tre treatment alleviates Cd-induced cytotoxicity in rPT cells by inhibiting apoptosis and restoring autophagic flux. PMID:29022917

Reduced Renal Methylarginine Metabolism Protects against Progressive Kidney Damage

PubMed Central

Caplin, Ben; Boruc, Olga; Bruce-Cobbold, Claire; Cutillas, Pedro; Dormann, Dirk; Faull, Peter; Grossman, Rebecca C.; Khadayate, Sanjay; Mas, Valeria R.; Nitsch, Dorothea D.; Wang, Zhen; Norman, Jill T.; Wilcox, Christopher S.; Wheeler, David C.; Leiper, James

2015-01-01

Nitric oxide (NO) production is diminished in many patients with cardiovascular and renal disease. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NO synthesis, and elevated plasma levels of ADMA are associated with poor outcomes. Dimethylarginine dimethylaminohydrolase-1 (DDAH1) is a methylarginine-metabolizing enzyme that reduces ADMA levels. We reported previously that a DDAH1 gene variant associated with increased renal DDAH1 mRNA transcription and lower plasma ADMA levels, but counterintuitively, a steeper rate of renal function decline. Here, we test the hypothesis that reduced renal-specific ADMA metabolism protects against progressive renal damage. Renal DDAH1 is expressed predominately within the proximal tubule. A novel proximal tubule–specific Ddah1 knockout (Ddah1PT−/−) mouse demonstrated tubular cell accumulation of ADMA and lower NO concentrations, but unaltered plasma ADMA concentrations. Ddah1PT−/− mice were protected from reduced kidney tissue mass, collagen deposition, and profibrotic cytokine expression in two independent renal injury models: folate nephropathy and unilateral ureteric obstruction. Furthermore, a study of two independent kidney transplant cohorts revealed higher levels of human renal allograft methylarginine-metabolizing enzyme gene expression associated with steeper function decline. We also report an association among DDAH1 expression, NO activity, and uromodulin expression supported by data from both animal and human studies, raising the possibility that kidney DDAH1 expression exacerbates renal injury through uromodulin-related mechanisms. Together, these data demonstrate that reduced renal tubular ADMA metabolism protects against progressive kidney function decline. Thus, circulating ADMA may be an imprecise marker of renal methylarginine metabolism, and therapeutic ADMA reduction may even be deleterious to kidney function. PMID:25855779

Missense mutation T485S alters NBCe1-A electrogenicity causing proximal renal tubular acidosis

PubMed Central

Shao, Xuesi M.; Kao, Liyo; Azimov, Rustam; Weinstein, Alan M.; Newman, Debra; Liu, Weixin; Kurtz, Ira

2013-01-01

Mutations in SLC4A4, the gene encoding the electrogenic Na+-HCO3− cotransporter NBCe1, cause severe proximal renal tubular acidosis (pRTA), growth retardation, decreased IQ, and eye and teeth abnormalities. Among the known NBCe1 mutations, the disease-causing mechanism of the T485S (NBCe1-A numbering) mutation is intriguing because the substituted amino acid, serine, is structurally and chemically similar to threonine. In this study, we performed intracellular pH and whole cell patch-clamp measurements to investigate the base transport and electrogenic properties of NBCe1-A-T485S in mammalian HEK 293 cells. Our results demonstrated that Ser substitution of Thr485 decreased base transport by ∼50%, and importantly, converted NBCe1-A from an electrogenic to an electroneutral transporter. Aqueous accessibility analysis using sulfhydryl reactive reagents indicated that Thr485 likely resides in an NBCe1-A ion interaction site. This critical location is also supported by the finding that G486R (a pRTA causing mutation) alters the position of Thr485 in NBCe1-A thereby impairing its transport function. By using NO3− as a surrogate ion for CO32−, our result indicated that NBCe1-A mediates electrogenic Na+-CO32− cotransport when functioning with a 1:2 charge transport stoichiometry. In contrast, electroneutral NBCe1-T485S is unable to transport NO3−, compatible with the hypothesis that it mediates Na+-HCO3− cotransport. In patients, NBCe1-A-T485S is predicted to transport Na+-HCO3− in the reverse direction from blood into proximal tubule cells thereby impairing transepithelial HCO3− absorption, possibly representing a new pathogenic mechanism for generating human pRTA. PMID:23636456

Insights from mathematical modeling of renal tubular function.

PubMed

Weinstein, A M

1998-01-01

Mathematical models of proximal tubule have been developed which represent the important solute species within the constraints of known cytosolic concentrations, transport fluxes, and overall epithelial permeabilities. In general, model simulations have been used to assess the quantitative feasibility of what appear to be qualitatively plausible mechanisms, or alternatively, to identify incomplete rationalization of experimental observations. The examples considered include: (1) proximal water reabsorption, for which the lateral interspace is a locus for solute-solvent coupling; (2) ammonia secretion, for which the issue is prioritizing driving forces - transport on the Na+/H+ exchanger, on the Na,K-ATPase, or ammoniagenesis; (3) formate-stimulated NaCl reabsorption, for which simple addition of a luminal membrane chloride/formate exchanger fails to represent experimental observation, and (4) balancing luminal entry and peritubular exit, in which ATP-dependent peritubular K+ channels have been implicated, but appear unable to account for the bulk of proximal tubule cell volume homeostasis.

Segmental heterogeneity in Bcl-2, Bcl-xL and Bax expression in rat tubular epithelium after ischemia-reperfusion.

PubMed

Valdés, Francisco; Pásaro, Eduardo; Díaz, Inmaculada; Centeno, Alberto; López, Eduardo; García-Doval, Sandra; González-Roces, Severino; Alba, Alfonso; Laffon, Blanca

2008-06-01

Studies in rats with bilateral clamping of renal arteries showed transient Bcl-2, Bcl-xL and Bax expression in renal tubular epithelium following ischemia-reperfusion. However, current data on the preferential localization of specific mRNAs or proteins are limited because gene expression was not analysed at segmental level. This study analyses the mRNA expression of Bcl-2, Bcl-xL and Bax in four segments of proximal and distal tubules localized in the renal cortex and outer medulla in rat kidneys with bilateral renal clamping for 30 min and seven reperfusion times versus control animals without clamp. Proximal convoluted tubule (PCT), distal convoluted tubule (DCT), proximal straight tubule (PST) and medullary thick ascending limb (MTAL) were obtained by manual microdissection. RT-PCR was used to analyse mRNA expression at segmental level. Proximal convoluted tubule and MTAL showed early, persistent and balanced up-regulation of Bcl-2, Bcl-xL and Bax, while PST and DCT revealed only Bcl-2 and Bcl-xL, when only Bax was detected in PST. DCT expressed Bcl-xL initially, and persistent Bcl-2 later. These patterns suggest a heterogeneous apoptosis regulatory response in rat renal tubules after ischemia-reperfusion, independently of cortical or medullary location. This heterogeneity of the expression patterns of Bcl-2 genes could explain the different susceptibility to undergo apoptosis, the different threshold to ischemic damage and the different adaptive capacity to injury among these tubular segments.

Early treatment with xenon protects against the cold ischemia associated with chronic allograft nephropathy in rats.

PubMed

Zhao, Hailin; Luo, Xianghong; Zhou, Zhaowei; Liu, Juying; Tralau-Stewart, Catherine; George, Andrew J T; Ma, Daqing

2014-01-01

Chronic allograft nephropathy (CAN) is a common finding in kidney grafts with functional impairment. Prolonged hypothermic storage-induced ischemia-reperfusion injury is associated with the early onset of CAN. As the noble gas xenon is clinically used as an anesthetic and has renoprotective properties in a rodent model of ischemia-reperfusion injury, we studied whether early treatment with xenon could attenuate CAN associated with prolonged hypothermic storage. Exposure to xenon enhanced the expression of insulin growth factor-1 (IGF-1) and its receptor in human proximal tubular (HK-2) cells, which, in turn, increased cell proliferation. Xenon treatment before or after hypothermia-hypoxia decreased cell apoptosis and cell inflammation after reoxygenation. The xenon-induced HK-2 cell proliferation was abolished by blocking the IGF-1 receptor, mTOR, and HIF-1α individually. In the Fischer-to-Lewis rat allogeneic renal transplantation model, xenon exposure of donors before graft retrieval or recipients after engraftment enhanced tubular cell proliferation and decreased tubular cell death and cell inflammation associated with ischemia-reperfusion injury. Compared with control allografts, xenon treatment significantly suppressed T-cell infiltration and fibrosis, prevented the development of CAN, and improved renal function. Thus, xenon treatment promoted recovery from ischemia-reperfusion injury and reduced susceptibility to the subsequent development of CAN in allografts.

Ischemic acute renal failure and antioxidant therapy in the rat. The relation between glomerular and tubular dysfunction.

PubMed Central

Bird, J E; Milhoan, K; Wilson, C B; Young, S G; Mundy, C A; Parthasarathy, S; Blantz, R C

1988-01-01

The effects of antioxidant therapy with probucol were evaluated in rats subjected to 1 h renal ischemia and to 24 h reperfusion. Probucol exerted significant antioxidant effects in renal cortical tubules in vitro when exposed to a catalase-resistant oxidant. At 24 h probucol treatment (IP) improved single nephron glomerular filtration rate (SNGFR) (28.1 +/- 3.3 nl/min) in comparison to untreated ischemic (I) rats (15.2 +/- 3.0), primarily as a result of improving SNGFR in a population of low SNGFR, low flow and/or obstructed nephrons. However, absolute proximal reabsorption remained abnormally low in IP rats at 24 h (5.9 +/- 0.8 nl/min), and cell necrosis was greater than in I rats. Kidney GFR remained low in IP rats due to extensive tubular backleak of inulin measured by microinjection studies. Evaluations after 2 h of reperfusion revealed a higher SNGFR in IP (36 +/- 3.1 nl/min) than I rats (20.8 +/- 2.7 nl/min). Absolute proximal reabsorption was essentially normal (11.6 +/- 1.3 nl/min) in IP rats, which was higher than IP rats at 24 h and the concurrent I rats. Administration of the lipophilic antioxidant, probucol, increased SNGFR and proximal tubular reabsorption within 2 h after ischemic renal failure. Although SNGFR remained higher than I rats at 24 h, absolute reabsorption fell below normal levels and tubular necrosis was more extensive in IP rats. Early improvement in nephron filtration with antioxidants may increase load dependent metabolic demand upon tubules and increase the extent of damage and transport dysfunction. Images PMID:2835399

Evidence for an Intrinsic Renal Tubular Defect in Mice with Genetic Hypophosphatemic Rickets

PubMed Central

Cowgill, Larry D.; Goldfarb, Stanley; Lau, Kai; Slatopolsky, Eduardo; Agus, Zalman S.

1979-01-01

To investigate the role of parathyroid hormone (PTH) and(or) an intrinsic renal tubular reabsorptive defect for phosphate in mice with hereditary hypophosphatemic rickets, we performed clearance and micropuncture studies in hypophosphatemic mutants and nonaffected littermate controls. Increased fractional excretion of phosphate in mutants (47.2±4 vs. 30.8±2% in controls) was associated with reduced fractional and absolute reabsorption in the proximal convoluted tubule and more distal sites. Acute thyropara-thyroidectomy (TPTX) increased phosphate reabsorption in both mutants and controls with a fall in fractional phosphate excretion to ≅7.5% in both groups indicating that PTH modified the degree of phosphaturia in the intact mutants. Absolute reabsorption in the proximal tubule and beyond remained reduced in the mutants, however, possibly because of the reduced filtered load. Serum PTH levels were the same in intact mutants and normals as was renal cortical adenylate cyclase activity both before and after PTH stimulation. To evaluate the possibility that the phosphate wasting was caused by an intrinsic tubular defect that was masked by TPTX, glomerular fluid phosphate concentration was raised by phosphate infusion in TPTX mutants to levels approaching those of control mice. Phosphate excretion rose markedly and fractional reabsorption fell, but there was no change in absolute phosphate reabsorption in either the proximal tubule or beyond, indicating a persistent reabsorptive defect in the absence of PTH. We conclude that hereditary hypophosphatemia in the mouse is associated with a renal tubular defect in phosphate reabsorption, which is independent of PTH and therefore represents a specific intrinsic abnormality of phosphate transport. PMID:221535

Determination of Clara cell protein urinary elimination as a marker of tubular dysfunction.

PubMed

Martín-Granado, Ascensión; Vázquez-Moncholí, Carmen; Luis-Yanes, María Isabel; López-Méndez, Marisela; García-Nieto, Víctor

2009-04-01

Clara cell 16-kDa protein (CC16) is a protein expressed primarily by the bronchial cells. It is rapidly eliminated by glomerular filtration, reabsorbed almost entirely, and catabolized in proximal tubule cells. To date, normal values for urinary CC16 in healthy children have not been determined. We have studied 63 pediatric patients (mean age 8.17 +/- 3.91 years) and 31 healthy children (control group; mean age 8.83 +/- 3.65 years). In the control group, the CC16/creatinine ratio was 1.22 +/- 1.52 microg/g. In 16 out of 31 control children, the value of the ratio was zero. Fourteen patients (22.2%) showed a high CC16/creatinine ratio; in contrast, among these same patients, the ratio N-acetyl-beta-D: -glucosaminidase (NAG)/creatinine was elevated in seven cases (11.1%) and the ratio beta2-microglobulin/creatinine was elevated in seven cases (11.1%). The three parameters were in agreement in 51 patients (80.9%). Among the patients, the CC16/creatinine ratio was correlated with both the beta2-microglobulin/creatinina ratio (r = 0.76, P < 0.001) and the NAG/creatinine ratio (r = 0.6, P < 0.001). Our findings indicate that CC16 is a good marker of proximal tubular function in childhood. The highest observed values were in children with proximal tubulopathies, in children with chronic renal failure, and in those treated with cyclosporine.

Value of Renal Biopsy in Diagnosing Infantile Nephropathic Cystinosis Associated With Secondary Nephrogenic Diabetes Insipidus.

PubMed

Joyce, Emily; Ho, Jacqueline; El-Gharbawy, Areeg; Salgado, Cláudia M; Ranganathan, Sarangarajan; Reyes-Múgica, Miguel

2017-01-01

Cystinosis is the most common cause of inherited renal Fanconi syndrome in young children, and typically presents with laboratory findings of a proximal tubulopathy and corneal crystals by one year of age. We describe here renal biopsy findings in a 20-month-old patient with an atypical presentation of distal renal tubular acidosis, diabetes insipidus, and the absence of corneal crystals. Although renal biopsy is usually not necessary to establish the diagnosis of cystinosis, when the patient presents with atypical signs and symptoms, a renal biopsy may be extremely valuable. A 20-month-old boy presented with failure to thrive, polyuria, polydipsia, and rickets. He initially showed evidence of a renal tubular acidosis, mild renal insufficiency, and nephrogenic diabetes insipidus. His initial ophthalmologic examination did not demonstrate corneal crystals. His subsequent workup revealed phosphaturia, suggesting a partial proximal tubulopathy. Concomitantly, a renal biopsy revealed prominent podocytes with an immature glomerular appearance, and electron microscopy analysis showed numerous intracellular crystals within tubular epithelial cells. Subsequent laboratory and genetic testing confirmed a diagnosis of infantile nephropathic cystinosis. This case highlights the variability in the clinical presentation of cystinosis, resulting in an uncommon clinical picture of a rare disease. Given that treatment is available to prolong renal function and minimize the extra-renal manifestations of this disorder, early diagnosis is essential. It is important to raise the index of suspicion of cystinosis by recognizing its subtle morphological changes in young patients, and that nephrogenic diabetes insipidus can be secondary to this disorder.

Maturation of the renal response to hypertonic sodium chloride loading in rats: micropuncture and clearance studies.

PubMed Central

Baker, J T; Solomon, S

1976-01-01

1. The ability of maturing rats to excrete a sodium load was studied by micropuncture and clearance procedures. 2. During control conditions, no change of glomerular filtration rate or sodium excretion was observed for the time period of the entire procedure (P greater than 0-20). During the infusion of hypertonic (4%) sodium chloride, fractional sodium excretion was 0-08 +/- 0-01 in rats 21-30 days old and 0-14 +/- 0-01 (P less than 0-01) in adults. However, the depression of proximal tubular water re-absorption was equal in both groups (P greater than 0-20). 3. Proximal glomerulotubular balance for water re-absorption was similar in all groups (P less than 0-20). Since end proximal tubular water excretion and depression of fractional water excretion were the same in all animals, differences of urinary sodium excretion during development are probably due to differences of function of segments beyond the proximal tubule during development. 4. Fractional potassium excretion was reduced in young rats (0-17 +/- 0-04) during hypertonic sodium chloride infusion, compared to adults (0-24 +/- 0-01, P less than 0-05). 5. Passage time of fast green through cortical segments in seconds is prolonged in young rats during control conditions. Similar decreases of passage time were seen in all groups during hypertonic sodium chloride infusion. No segmental differences of passage time were seen during developmental. 6. No difference in the relationship between fractional sodium and water excretion was seen during development of the renal response to hypertonic sodium chloride infusion. Thus, altered sensitivity to sodium chloride osmotic diuresis does not exist during maturation in rats. PMID:945839

Atg5-mediated autophagy deficiency in proximal tubules promotes cell cycle G2/M arrest and renal fibrosis.

PubMed

Li, Huiyan; Peng, Xuan; Wang, Yating; Cao, Shirong; Xiong, Liping; Fan, Jinjin; Wang, Yihan; Zhuang, Shougang; Yu, Xueqing; Mao, Haiping

2016-09-01

Macroautophagy/autophagy protects against cellular stress. Renal sublethal injury-triggered tubular epithelial cell cycle arrest at G2/M is associated with interstitial fibrosis. However, the role of autophagy in renal fibrosis is elusive. Here, we hypothesized that autophagy activity in tubular epithelial cells is pivotal for inhibition of cell cycle G2/M arrest and subsequent fibrogenic response. In both renal epithelial cells stimulated by angiotensin II (AGT II) and the murine kidney after unilateral ureteral obstruction (UUO), we observed that occurrence of autophagy preceded increased production of COL1 (collagen, type I). Pharmacological enhancement of autophagy by rapamycin suppressed COL1 accumulation and renal fibrosis. In contrast, genetic ablation of autophagy by proximal tubular epithelial cell-specific deletion of Atg5, with reduction of the LC3-II protein level and degradation of SQSTM1/p62, showed marked cell cycle arrest at the G2/M phase, robust COL1 deposition, and severe interstitial fibrosis in a UUO model, as compared with wild-type mice. In vitro, AGT II exposure triggered autophagy preferentially in the G1/S phase, and increased COL1 expression in the G2/M phase in renal epithelial cells. Stimulation of Atg5-deficient primary proximal tubular cells with AGT II also resulted in elevated G2/M arrest and COL1 production. Pharmacological or genetic inhibition of autophagy increased AGT II-mediated G2/M arrest. Enhanced expression of ATG5, but not the autophagy-deficient ATG5 mutant K130R, rescued the G2/M arrest, suggesting the regulation of cell cycle progression by ATG5 is autophagy dependent. In conclusion, Atg5-mediated autophagy in proximal epithelial cells is a critical host-defense mechanism that prevents renal fibrosis by blocking G2/M arrest.

[Genetic hypophosphatemia: recent advances in physiopathogenic concept].

PubMed

Beraud, G; Perimenis, P; Velayoudom, Fr-L; Wemeau, J-L; Vantyghem, M-Chr

2005-04-01

Renal proximal tubular reabsorption of phosphate and intestinal absorption both regulate phosphate homeostasis. Brush-border membrane Npt2a cotransporter is the key element in proximal tubular P (i) reabsorption. Inactivating mutations of Npt2a cause bone demineralisation and urolithiasis. An excess of a phosphaturic factor, called "Phosphatonin", could modulate phosphate reabsorption by inhibition on Npt2a. Inactivating mutation of PHEX, an endopeptidase-membrane coding gene, is responsible for X-linked Hypophosphatemia (XLH), because of an impaired degradation of phosphatonine by PHEX product. Autosomic Dominant Hypophosphatemic Rickets (ADHR) is explained by a mutation preventing FGF23 (one of the best identified phosphatonines) from cleavage. According recent data, FGF23, MEPE (Matrix Extracellular Phosphoglycoprotein) et FRP4 (frizzled related protein-4) are 3 putative "phosphatonines".

Primary hyperparathyroidism and proximal renal tubular acidosis: Report of two cases

PubMed Central

Siddiqui, Abdullah A.; Wilson, Douglas R.

1972-01-01

Two cases of primary hyperparathyroidism due to single parathyroid adenomas presented with the additional feature of hyperchloremic acidosis. The defect in urinary acidification responsible was not of the distal or gradient-limited type since both patients could lower urine pH adequately. However, there was a defect of bicarbonate reabsorption, an abnormality referred to as the proximal or rate-limited type of renal tubular acidosis. It is suggested that this defect represents an exaggeration of the physiological effect of parathormone on bicarbonate reabsorption and may be responsible for the frequent finding of hyperchloremia in association with primary hyperparathyroidism as well as for the urinary bicarbonate-wasting associated with a variety of causes of secondary hyperparathyroidism. PMID:5012229

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruner, R.H.

Male and female Fischer-344 rats and female C57/BL6 mice were subjected to subchronic and chronic inhalation exposures to a variety of distillate and synthetic hydrocarbon fuels of military interest. In general, male rats exposed to all agents developed a dose-related nephropathy which was not observed in females, controls, or exposed mice. Kidney lesions consisted of greatly increased cytoplasmic hyaline droplets in proximal tubular epithelium, necrosis of proximal tubular cells, and intratubular plugs of necrotic cell debris at the junction of the outer and inner stripe of the outer medulla. Following exposure, males that were held for lifetime oncogenic evaluation exhibitedmore » abundant mineralized casts in medullary tubules, multifocal to diffuse papillary hyperplasia of pelvic urothelium, and accentuated tubular degeneration compatible with progressive nephrosis of old rats. Male rats exposed six hours/day, five days/week for one year to two synthetic hydrocarbon missile fuels had significant increases in renal cell tumors, whereas males exposed for 90 days continuously to various distillate fuels failed to develop increased kidney neoplasia following lifespan observation. The pathogenic mechanisms remain unclear, but it is proposed that kidney changes may be related to an inability of renal tubular cells to efficiently digest resorbed alpha 2u globulin - a special protein of male rats which is synthesized in the liver.« less

Reduced Renal Methylarginine Metabolism Protects against Progressive Kidney Damage.

PubMed

Tomlinson, James A P; Caplin, Ben; Boruc, Olga; Bruce-Cobbold, Claire; Cutillas, Pedro; Dormann, Dirk; Faull, Peter; Grossman, Rebecca C; Khadayate, Sanjay; Mas, Valeria R; Nitsch, Dorothea D; Wang, Zhen; Norman, Jill T; Wilcox, Christopher S; Wheeler, David C; Leiper, James

2015-12-01

Nitric oxide (NO) production is diminished in many patients with cardiovascular and renal disease. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NO synthesis, and elevated plasma levels of ADMA are associated with poor outcomes. Dimethylarginine dimethylaminohydrolase-1 (DDAH1) is a methylarginine-metabolizing enzyme that reduces ADMA levels. We reported previously that a DDAH1 gene variant associated with increased renal DDAH1 mRNA transcription and lower plasma ADMA levels, but counterintuitively, a steeper rate of renal function decline. Here, we test the hypothesis that reduced renal-specific ADMA metabolism protects against progressive renal damage. Renal DDAH1 is expressed predominately within the proximal tubule. A novel proximal tubule-specific Ddah1 knockout (Ddah1(PT-/-)) mouse demonstrated tubular cell accumulation of ADMA and lower NO concentrations, but unaltered plasma ADMA concentrations. Ddah1(PT-/-) mice were protected from reduced kidney tissue mass, collagen deposition, and profibrotic cytokine expression in two independent renal injury models: folate nephropathy and unilateral ureteric obstruction. Furthermore, a study of two independent kidney transplant cohorts revealed higher levels of human renal allograft methylarginine-metabolizing enzyme gene expression associated with steeper function decline. We also report an association among DDAH1 expression, NO activity, and uromodulin expression supported by data from both animal and human studies, raising the possibility that kidney DDAH1 expression exacerbates renal injury through uromodulin-related mechanisms. Together, these data demonstrate that reduced renal tubular ADMA metabolism protects against progressive kidney function decline. Thus, circulating ADMA may be an imprecise marker of renal methylarginine metabolism, and therapeutic ADMA reduction may even be deleterious to kidney function. Copyright © 2015 by the American Society of Nephrology.

A Microperfusion Study of Bicarbonate Accumulation in the Proximal Tubule of the Rat Kidney*

PubMed Central

Bank, Norman; Aynedjian, Hagop S.

1967-01-01

In order to determine whether HCO3- gains access to the proximal tubular lumen from a source other than the glomerular filtrate, we carried out microperfusion experiments on isolated segments of rat proximal tubules in vivo. The perfusion fluid was essentially free of HCO3- and of a composition that prevented net absorption of sodium and water. It was found that when plasma HCO3- concentration and CO2 tension (PCO2) were normal, the HCO3- concentration in the collected perfusate rose to about 3 mEq per L. Inhibition of renal carbonic anhydrase did not produce an appreciable change in this value in normal rats, but when the enzyme was inhibited in acutely alkalotic rats, a mean concentration of 15 mEq per L was recovered in the perfusate. Addition of HCO3- to the tubular lumen might occur by either intraluminal generation of HCO3- from CO2 and OH- or by influx of ionic bicarbonate from the plasma or tubular cells. Because of the marked increase in HCO3- found when intraluminal carbonic anhydrase was inhibited, generation of new HCO3- from CO2 and OH- seems unlikely. We conclude, therefore, that influx of ionic bicarbonate occurred, either across the luminal membrane or through extracellular aqueous channels. These observations suggest that the proximal epithelium has a finite degree of permeability to HCO3- and that influx of this ion may be a component of the over-all handling of HCO3- by the kidney. PMID:4959907

Nerve regeneration using tubular scaffolds from biodegradable polyurethane.

PubMed

Hausner, T; Schmidhammer, R; Zandieh, S; Hopf, R; Schultz, A; Gogolewski, S; Hertz, H; Redl, H

2007-01-01

In severe nerve lesion, nerve defects and in brachial plexus reconstruction, autologous nerve grafting is the golden standard. Although, nerve grafting technique is the best available approach a major disadvantages exists: there is a limited source of autologous nerve grafts. This study presents data on the use of tubular scaffolds with uniaxial pore orientation from experimental biodegradable polyurethanes coated with fibrin sealant to regenerate a 8 mm resected segment of rat sciatic nerve. Tubular scaffolds: prepared by extrusion of the polymer solution in DMF into water coagulation bath. The polymer used for the preparation of tubular scaffolds was a biodegradable polyurethane based on hexamethylene diisocyanate, poly(epsilon-caprolactone) and dianhydro-D-sorbitol. EXPERIMENTAL MODEL: Eighteen Sprague Dawley rats underwent mid-thigh sciatic nerve transection and were randomly assigned to two experimental groups with immediate repair: (1) tubular scaffold, (2) 180 degrees rotated sciatic nerve segment (control). Serial functional measurements (toe spread test, placing tests) were performed weekly from 3rd to 12th week after nerve repair. On week 12, electrophysiological assessment was performed. Sciatic nerve and scaffold/nerve grafts were harvested for histomorphometric analysis. Collagenic connective tissue, Schwann cells and axons were evaluated in the proximal nerve stump, the scaffold/nerve graft and the distal nerve stump. The implants have uniaxially-oriented pore structure with a pore size in the range of 2 micorm (the pore wall) and 75 x 700 microm (elongated pores in the implant lumen). The skin of the tubular implants was nonporous. Animals which underwent repair with tubular scaffolds of biodegradable polyurethanes coated with diluted fibrin sealant had no significant functional differences compared with the nerve graft group. Control group resulted in a trend-wise better electrophysiological recovery but did not show statistically significant differences. There was a higher level of collagenic connective tissue within the scaffold and within the distal nerve stump. Schwann cells migrated into the polyurethane scaffold. There was no statistical difference to the nerve graft group although Schwann cell counts were lower especially within the middle of the polyurethane scaffold. Axon counts showed a trend-wise decrease within the scaffold. These results suggest that biodegradable polyurethane tubular scaffolds coated with diluted fibrin sealant support peripheral nerve regeneration in a standard gap model in the rat up to 3 months. Three months after surgery no sign of degradation could be seen.

Toxicological Significance of Renal Bcrp: Another Potential Transporter in the Elimination of Mercuric Ions from Proximal Tubular Cells

PubMed Central

Bridges, Christy C.; Zalups, Rudolfs K.; Joshee, Lucy

2015-01-01

Secretion of inorganic mercury (Hg2+) from proximal tubular cells into the tubular lumen has been shown to involve the multidrug resistance-associated protein 2 (Mrp2). Considering similarities in localization and substrate specificity between Mrp2 and the breast cancer resistance protein (Bcrp), we hypothesize that Bcrp may also play a role in the proximal tubular secretion of mercuric species. In order to test this hypothesis, the uptake of Hg2+ was examined initially using inside-out membrane vesicles containing Bcrp. The results of these studies suggest that Bcrp may be capable of transporting certain conjugates of Hg2+. To further characterize the role of Bcrp in the handling of mercuric ions and in the induction of Hg2+-induced nephropathy, Sprague-Dawley and Bcrp knockout (bcrp−/−) rats were exposed intravenously to a non-nephrotoxic (0.5 μmol • kg−1), a moderately nephrotoxic (1.5 μmol • kg−1) or a significantly nephrotoxic (2.0 μmol • kg−1) dose of HgCl2. In general, the accumulation of Hg2+ was greater in organs of bcrp−/− rats than in Sprague-Dawley rats, suggesting that Bcrp may play a role in the export of Hg2+ from target cells. Within the kidney, cellular injury and necrosis was more severe in bcrp−/− rats than in controls. The pattern of necrosis, which was localized in the inner cortex and the outer stripe of the outer medulla was significantly different from that observed in Mrp2-deficient animals. These findings suggest that Bcrp may be involved in the cellular export of select mercuric species and that its role in this export may differ from that of Mrp2. PMID:25868844

Dragon enhances BMP signaling and increases transepithelial resistance in kidney epithelial cells.

PubMed

Xia, Yin; Babitt, Jodie L; Bouley, Richard; Zhang, Ying; Da Silva, Nicolas; Chen, Shanzhuo; Zhuang, Zhenjie; Samad, Tarek A; Brenner, Gary J; Anderson, Jennifer L; Hong, Charles C; Schneyer, Alan L; Brown, Dennis; Lin, Herbert Y

2010-04-01

The neuronal adhesion protein Dragon acts as a bone morphogenetic protein (BMP) coreceptor that enhances BMP signaling. Given the importance of BMP signaling in nephrogenesis and its putative role in the response to injury in the adult kidney, we studied the localization and function of Dragon in the kidney. We observed that Dragon localized predominantly to the apical surfaces of tubular epithelial cells in the thick ascending limbs, distal convoluted tubules, and collecting ducts of mice. Dragon expression was weak in the proximal tubules and glomeruli. In mouse inner medullary collecting duct (mIMCD3) cells, Dragon generated BMP signals in a ligand-dependent manner, and BMP4 is the predominant endogenous ligand for the Dragon coreceptor. In mIMCD3 cells, BMP4 normally signaled through BMPRII, but Dragon enhanced its signaling through the BMP type II receptor ActRIIA. Dragon and BMP4 increased transepithelial resistance (TER) through the Smad1/5/8 pathway. In epithelial cells isolated from the proximal tubule and intercalated cells of collecting ducts, we observed coexpression of ActRIIA, Dragon, and BMP4 but not BMPRII. Taken together, these results suggest that Dragon may enhance BMP signaling in renal tubular epithelial cells and maintain normal renal physiology.

Pretreatment by low-dose fibrates protects against acute free fatty acid-induced renal tubule toxicity by counteracting PPAR{alpha} deterioration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takahashi, Kyoko; Department of Nephrology Internal Medicine, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto, 390-8621; Kamijo, Yuji, E-mail: yujibeat@shinshu-u.ac.jp

2011-05-01

Development of a preventive strategy against tubular damage associated with proteinuria is of great importance. Recently, free fatty acid (FFA) toxicities accompanying proteinuria were found to be a main cause of tubular damage, which was aggravated by insufficiency of peroxisome proliferator-activated receptor alpha (PPAR{alpha}), suggesting the benefit of PPAR{alpha} activation. However, an earlier study using a murine acute tubular injury model, FFA-overload nephropathy, demonstrated that high-dose treatment of PPAR{alpha} agonist (0.5% clofibrate diet) aggravated the tubular damage as a consequence of excess serum accumulation of clofibrate metabolites due to decreased kidney elimination. To induce the renoprotective effects of PPAR{alpha} agonistsmore » without drug accumulation, we tried a pretreatment study using low-dose clofibrate (0.1% clofibrate diet) using the same murine model. Low-dose clofibrate pretreatment prevented acute tubular injuries without accumulation of its metabolites. The tubular protective effects appeared to be associated with the counteraction of PPAR{alpha} deterioration, resulting in the decrease of FFAs influx to the kidney, maintenance of fatty acid oxidation, diminution of intracellular accumulation of undigested FFAs, and attenuation of disease developmental factors including oxidative stress, apoptosis, and NF{kappa}B activation. These effects are common to other fibrates and dependent on PPAR{alpha} function. Interestingly, however, clofibrate pretreatment also exerted PPAR{alpha}-independent tubular toxicities in PPAR{alpha}-null mice with FFA-overload nephropathy. The favorable properties of fibrates are evident when PPAR{alpha}-dependent tubular protective effects outweigh their PPAR{alpha}-independent tubular toxicities. This delicate balance seems to be easily affected by the drug dose. It will be important to establish the appropriate dosage of fibrates for treatment against kidney disease and to develop a novel PPAR{alpha} activator that has a steady serum concentration regardless of kidney dysfunction. - Graphical Abstract: Massive proteinuria introduces free fatty acid toxicity to proximal tubular epithelial cells (PTECs). PPAR{alpha} activationvia clofibrate pretreatment maintains fatty acid catabolism and attenuates oxidative stress, apoptosis, and NF{kappa}B activation, resulting in protection of PTECs. The favorable properties of fibrates are evident when PPAR{alpha}-dependent tubular protective effects outweigh their PPAR{alpha}-independent tubular toxicities. Display Omitted Highlights: > Clofibrate pretreatment protects against acute FFA-induced tubular toxicity. > PPAR{alpha} activation decreases FFA influx and maintains fatty acid catabolism. > PPAR{alpha} activation attenuates oxidative stress, apoptosis, and NF{kappa}B activation. > Protective effects must outweigh PPAR{alpha}-independent tubular toxicities of fibrates.« less

Parabiosis and single-cell RNA sequencing reveal a limited contribution of monocytes to myofibroblasts in kidney fibrosis.

PubMed

Kramann, Rafael; Machado, Flavia; Wu, Haojia; Kusaba, Tetsuro; Hoeft, Konrad; Schneider, Rebekka K; Humphreys, Benjamin D

2018-05-03

Fibrosis is the common final pathway of virtually all chronic injury to the kidney. While it is well accepted that myofibroblasts are the scar-producing cells in the kidney, their cellular origin is still hotly debated. The relative contribution of proximal tubular epithelium and circulating cells, including mesenchymal stem cells, macrophages, and fibrocytes, to the myofibroblast pool remains highly controversial. Using inducible genetic fate tracing of proximal tubular epithelium, we confirm that the proximal tubule does not contribute to the myofibroblast pool. However, in parabiosis models in which one parabiont is genetically labeled and the other is unlabeled and undergoes kidney fibrosis, we demonstrate that a small fraction of genetically labeled renal myofibroblasts derive from the circulation. Single-cell RNA sequencing confirms this finding but indicates that these cells are circulating monocytes, express few extracellular matrix or other myofibroblast genes, and express many proinflammatory cytokines. We conclude that this small circulating myofibroblast progenitor population contributes to renal fibrosis by paracrine rather than direct mechanisms.

Acute and chronic effects of SGLT2 blockade on glomerular and tubular function in the early diabetic rat

PubMed Central

Rieg, Timo; Miracle, Cynthia; Mansoury, Hadi; Whaley, Jean; Vallon, Volker; Singh, Prabhleen

2012-01-01

Tubuloglomerular feedback (TGF) stabilizes nephron function from minute to minute and adapts to different steady-state inputs to maintain this capability. Such adaptation inherently renders TGF less efficient at buffering long-term disturbances, but the magnitude of loss is unknown. We undertook the present study to measure the compromise between TGF and TGF adaptation in transition from acute to chronic decline in proximal reabsorption (Jprox). As a tool, we blocked proximal tubule sodium-glucose cotransport with the SGLT2 blocker dapagliflozin in hyperglycemic rats with early streptozotocin diabetes, a condition in which a large fraction of proximal fluid reabsorption owes to SGLT2. Dapagliflozin acutely reduced proximal reabsorption leading to a 70% increase in early distal chloride, a saturated TGF response, and a major reduction in single nephron glomerular filtration rate (SNGFR). Acute and chronic effects on Jprox were indistinguishable. Adaptations to 10–12 days of dapagiflozin included increased reabsorption by Henle's loop, which caused a partial relaxation in the increased tone exerted by TGF that could be explained without desensitization of TGF. In summary, TGF contributes to long-term fluid and salt balance by mediating a persistent decline in SNGFR as the kidney adapts to a sustained decrease in Jprox. PMID:21940401

Podocyte-derived microparticles promote proximal tubule fibrotic signaling via p38 MAPK and CD36

PubMed Central

Munkonda, Mercedes N.; Akbari, Shareef; Landry, Chloe; Sun, Suzy; Xiao, Fengxia; Turner, Maddison; Holterman, Chet E.; Nasrallah, Rania; Hébert, Richard L.; Kennedy, Christopher R. J.; Burger, Dylan

2018-01-01

ABSTRACT Tubulointerstitial fibrosis is a hallmark of advanced diabetic kidney disease that is linked to a decline in renal function, however the pathogenic mechanisms are poorly understood. Microparticles (MPs) are 100–1000 nm vesicles shed from injured cells that are implicated in intercellular signalling. Our lab recently observed the formation of MPs from podocytes and their release into urine of animal models of type 1 and 2 diabetes and in humans with type 1 diabetes. The purpose of the present study was to examine the role of podocyte MPs in tubular epithelial cell fibrotic responses. MPs were isolated from the media of differentiated, untreated human podocytes (hPODs) and administered to cultured human proximal tubule epithelial cells (PTECs). Treatment with podocyte MPs increased p38 and Smad3 phosphorylation and expression of the extracellular matrix (ECM) proteins fibronectin and collagen type IV. MP-induced responses were attenuated by co-treatment with the p38 inhibitor SB202190. A transforming growth factor beta (TGF-β) receptor inhibitor (LY2109761) blocked MP-induced Smad3 phosphorylation and ECM protein expression but not p38 phosphorylation suggesting that these responses occurred downstream of p38. Finally, blockade of the class B scavenger receptor CD36 completely abrogated MP-mediated p38 phosphorylation, downstream Smad3 activation and fibronectin/collagen type IV induction. Taken together our results suggest that podocyte MPs interact with proximal tubule cells and induce pro-fibrotic responses. Such interactions may contribute to the development of tubular fibrosis in glomerular disease. PMID:29435202

Clinicopathologic characteristics of light chain proximal tubulopathy with light chain inclusions involving multiple renal cell types
.

PubMed

Li, Xiaomei; Xu, Feng; Liang, Dandan; Liang, Shaoshan; Zhu, Xiaodong; Zhang, Mingchao; Huang, Xianghua; Liu, Zhihong; Zeng, Caihong

2018-02-01

Light chain proximal tubulopathy (LCPT) associated with plasma cell dyscrasias is a rare abnormality, especially cases involving multiple cell types. The aim of this study is to explore the characteristics and outcomes of these diseases. We comprehensively evaluated the clinical-pathological data, treatment, and outcomes of 6 LCPT patients with involvement of multiple cell types. In 3 cases, we found that the inclusions largely existed in tubular cells, while in 2 cases they coexisted in podocytes and tubular cells, and in 1 case they coexisted in histiocytes and tubular cells. The stain features and appearances of inclusions were specific and varied. Five patients displayed κ-light chains with crystal formation, while 1 patient displayed a λ subtype with increased lysosomes instead of crystals. Six patients presented with proteinuria, 4 with renal insufficiency, and 4 with complete or partial Fanconi syndrome. Our findings indicate that tubular cells are the most common location of cytoplasmic inclusions. Cases with κ-light chain storage are more common than λ, and the formation of crystals may be associated with the subtype of light chains. Immunoelectron microscopy could be used to increase sensitivity for the detection and location of monoclonal light chains. Therefore, these patients have some common clinical features with varied pathologic characteristics and prognoses but the same subtype of light chains.
.

Transforming growth factor-β1 receptor inhibition preserves glomerulotubular integrity during ureteral obstruction in adults but worsens injury in neonatal mice

PubMed Central

Galarreta, Carolina I.; Thornhill, Barbara A.; Forbes, Michael S.; Simpkins, Lauren N.; Kim, Dae-Kee

2013-01-01

Unilateral ureteral obstruction (UUO), a widely used model of chronic kidney disease and congenital obstructive uropathy, causes proximal tubular injury and formation of atubular glomeruli. Because transforming growth factor-β1 (TGF-β1) is a central regulator of renal injury, neonatal and adult mice were subjected to complete UUO while under general anesthesia and treated with vehicle or ALK5 TGF-β1 receptor inhibitor (IN-1130, 30 mg·kg−1·day−1). After 14 days, glomerulotubular integrity and proximal tubular mass were determined by morphometry of Lotus tetragonolobus lectin distribution, and the fraction of atubular glomeruli was determined by serial section analysis of randomly selected individual glomeruli. Glomerular area, macrophage infiltration, fibronectin distribution, and interstitial collagen were measured by morphometry. Compared with placebo, inhibition of TGF-β1 by IN-1130 decreased apoptosis and formation of atubular glomeruli, prevented parenchymal loss, increased glomerular area and glomerulotubular integrity, and increased proximal tubule fraction of the adult obstructed kidney parenchyma from 17 to 30% (P < 0.05, respectively). IN-1130 decreased macrophage infiltration and fibronectin and collagen deposition in the adult obstructed kidney by ∼50% (P < 0.05, respectively). In contrast to these salutary effects in the adult, IN-1130 caused widespread necrosis in obstructed neonatal kidneys. We conclude that whereas IN-1130 reduces obstructive injury in adult kidneys through preservation of glomerulotubular integrity and proximal tubular mass, TGF-β1 inhibition aggravates obstructive injury in neonates. These results indicate that while caution is necessary in treating congenital uropathies, ALK5 inhibitors may prevent nephron loss due to adult kidney disease. PMID:23303407

Neurogenic regulation of renal tubular sodium reabsorption.

PubMed

DiBona, G F

1977-08-01

The evidence supporting a role for direct neurogenic control of renal tubular sodium reabsorption is reviewed. Electron microscopic and fluorescence histochemical studies have demonstrated adrenergic nerve terminals in direct contact with basement membranes of mammalian (rat, dog, and monkey) renal tubular epithelial cells. Low-level direct or baroreceptor reflex stimulation of renal sympathetic nerves produces an increase in renal tubular sodium reabsorption without alterations in glomerular filtration rate, renal blood flow, or intrarenal distribution of blood flow. Antinatriuresis was prevented by prior treatment of the kidney with guanethidine or phenoxybenzamine. Rat kidney micropuncture studies have localized a site of enhanced tubular sodium reabsorption to the proximal tubule. Possible indirect mediation of the antinatriuresis by other humoral agents known to be released from the kidney on renal nerve stimulation (angiotensin II, prostaglandin) was excluded by experiments with appropriate blocking agents. The possible effects of anesthesia and uncertainties about the completeness of surgical renal denervation and other tubular segmental sites of action are critically analyzed. The clinical implications of this mechanism in pathologic conditions of sodium and water retention are discussed and and a prospectus for future work is presented.

Protective effects of L-type fatty acid-binding protein (L-FABP) in proximal tubular cells against glomerular injury in anti-GBM antibody-mediated glomerulonephritis

PubMed Central

Kanaguchi, Yasuhiko; Suzuki, Yusuke; Osaki, Ken; Sugaya, Takeshi; Horikoshi, Satoshi

2011-01-01

Background. In glomerulonephritis (GN), an overload of free fatty acids (FFA) bound to albumin in urinary protein may induce oxidative stress in the proximal tubules. Human liver-type fatty acid-binding protein (hL-FABP) expressed in human proximal tubules, but not rodents, participates in intracellular FFA metabolism and exerts anti-oxidative effects on the progression of tubulointerstitial damage. We examined whether tubular enhancement of this anti-oxidative action modulates the progression of glomerular damage in immune-mediated GN in hL-FABP chromosomal gene transgenic (Tg) mice. Methods. Anti-glomerular basement membrane antibody-induced glomerulonephritis (anti-GBM GN) was induced in Tg and wild-type mice (WT). Proteinuria, histopathology, polymorphonuclear (PMN) influx, expression of tubulointerstitial markers for oxidative stress 4-hydroxy-2-Nonenal (HNE) and fibrosis (α-smooth muscle actin), proximal tubular damage (Kim-1), Peroxisome Proliferator-Activated Receptor γ (PPAR γ) and inflammatory cytokines [Monocyte Chemotactic Protein-1, tumor necrosis factor-alpha (TNF-α) and Transforming growth factor beta (TGF-β)] were analyzed. The mice were also treated with an angiotensin type II receptor blocker (ARB). Results. The urinary protein level in Tg mice decreased significantly during the acute phase (∼Day 5). Tg mice survived for a significantly longer time than WT mice, with an attenuation of tubulointerstitial damage score and expression of each tubulointerstitial damage marker observed at Day 7. Expression of inflammatory cytokines on Day 7 was higher in WT mice than Tg mice and correlated strongly with PPARγ expression in WT mice, but not in Tg mice. Interestingly, Tg mice showed insufficient PMN influx at 3 and 6 h, with simultaneous elevation of urinary L-FABP and reduction in HNE expression. The two strains of mice showed different types of glomerular damage, with mild mesangial proliferation in Tg mice and severe endothelial swelling with vascular thrombosis in WT mice. The glomerular damage in Tg mice was improved by administration of an ARB. Conclusions. The present experimental model suggests that tubular enhancement of L-FABP may protect mice with anti-GBM GN from progression of both tubulointerstitial and glomerular injury. PMID:21525165

Protective effects of L-type fatty acid-binding protein (L-FABP) in proximal tubular cells against glomerular injury in anti-GBM antibody-mediated glomerulonephritis.

PubMed

Kanaguchi, Yasuhiko; Suzuki, Yusuke; Osaki, Ken; Sugaya, Takeshi; Horikoshi, Satoshi; Tomino, Yasuhiko

2011-11-01

In glomerulonephritis (GN), an overload of free fatty acids (FFA) bound to albumin in urinary protein may induce oxidative stress in the proximal tubules. Human liver-type fatty acid-binding protein (hL-FABP) expressed in human proximal tubules, but not rodents, participates in intracellular FFA metabolism and exerts anti-oxidative effects on the progression of tubulointerstitial damage. We examined whether tubular enhancement of this anti-oxidative action modulates the progression of glomerular damage in immune-mediated GN in hL-FABP chromosomal gene transgenic (Tg) mice. Anti-glomerular basement membrane antibody-induced glomerulonephritis (anti-GBM GN) was induced in Tg and wild-type mice (WT). Proteinuria, histopathology, polymorphonuclear (PMN) influx, expression of tubulointerstitial markers for oxidative stress 4-hydroxy-2-Nonenal (HNE) and fibrosis (α-smooth muscle actin), proximal tubular damage (Kim-1), Peroxisome Proliferator-Activated Receptor γ (PPAR γ) and inflammatory cytokines [Monocyte Chemotactic Protein-1, tumor necrosis factor-alpha (TNF-α) and Transforming growth factor beta (TGF-β)] were analyzed. The mice were also treated with an angiotensin type II receptor blocker (ARB). The urinary protein level in Tg mice decreased significantly during the acute phase (~Day 5). Tg mice survived for a significantly longer time than WT mice, with an attenuation of tubulointerstitial damage score and expression of each tubulointerstitial damage marker observed at Day 7. Expression of inflammatory cytokines on Day 7 was higher in WT mice than Tg mice and correlated strongly with PPARγ expression in WT mice, but not in Tg mice. Interestingly, Tg mice showed insufficient PMN influx at 3 and 6 h, with simultaneous elevation of urinary L-FABP and reduction in HNE expression. The two strains of mice showed different types of glomerular damage, with mild mesangial proliferation in Tg mice and severe endothelial swelling with vascular thrombosis in WT mice. The glomerular damage in Tg mice was improved by administration of an ARB. The present experimental model suggests that tubular enhancement of L-FABP may protect mice with anti-GBM GN from progression of both tubulointerstitial and glomerular injury.

Hemodynamic and renal implications of sodium-glucose cotransporter- 2 inhibitors in type 2 diabetes mellitus.

PubMed

Tejedor Jorge, Alberto

2016-11-01

In DM2, there is increased expression of the proximal glucose transporter SGLT2. The increased glucose reabsorption from the urine to the proximal tubule and subsequently to the bloodstream, has three direct effects on the prognosis of patients with DM2: a) it increases the daily glucose load by raising the renal threshold for glucose, thus augmenting requirements for oral antidiabetics and insulin. This progressive increase occurs throughout the course of the disease and in parallel with the increase in renal mass (renal hypertrophy); b) because of the greater glucose reabsorption, glycosuria is lower than the level corresponding to glycaemia, decreasing the stimulus on the tubuloglomerular feedback system of the distal nephron. As a result, the glomerular vasodilation caused by hyperglycaemia is not arrested, maintaining glomerular hyperfiltration, and c) the excess glucose transported to the proximal tubular cells modifies their redox status, increasing local production of glycosylating products and activating local production of proinflammatory and profibrotic proliferative mediators. These mediators are responsible for the direct free radical damage to proximal tubular cells, for increased SGLT2 expression, increased production of collagen IV and extracellular matrix, and activation of monocyte/macrophages able to cause endothelial injury. The use of SGLT2 inhibitors not only reduces the reabsorption of glucose from the glomerular filtrate back into the circulationthus improving metabolic control in diabetesbut also restores tubuloglomerular feedback by increasing glycosuria and distal urinary flow. However, the most notable effect is due to inhibition of glucose entry to the proximal tubular cells. Glycosuria is toxic to the kidney: it harms glucosetransporting cells, that is, the proximal cells, which contain SGLT2. In animal models, SGLT2 inhibition reduces local production of oxygen-free radicals, the formation of mesangial matrix and collagen IV, glomerular infiltration by inflammatory cells and monocyte/macrophage-dependent arteriosclerosis. In humans, SGLT2 have a demonstrated ability to reduce renal injury and cardiovascular risk in patients with type 2 diabetes mellitus. Copyright © 2016 Elsevier España, S.L.U. All rights reserved.

Grouper tshβ Promoter-Driven Transgenic Zebrafish Marks Proximal Kidney Tubule Development

PubMed Central

Wang, Yang; Sun, Zhi-Hui; Zhou, Li; Li, Zhi; Gui, Jian-Fang

2014-01-01

Kidney tubule plays a critical role in recovering or secreting solutes, but the detailed morphogenesis remains unclear. Our previous studies have found that grouper tshβ (gtshβ) is also expressed in kidney, however, the distribution significance is still unknown. To understand the gtshβ role and kidney tubule morphogenesis, here, we have generated a transgenic zebrafish line Tg(gtshβ:GFP) with green fluorescent protein driven by the gtshβ promoter. Similar to the endogenous tshβ in zebrafish or in grouper, the gtshβ promoter-driven GFP is expressed in pituitary and kidney, and the developing details of proximal kidney tubule are marked in the transgenic zebrafish line. The gfp initially transcribes at 16 hours post fertilization (hpf) above the dorsal mesentery, and partially co-localizes with pronephric tubular markers slc20a1a and cdh17. Significantly, the GFP specifically localizes in proximal pronephric segments during embryogenesis and resides at kidney duct epithelium in adult fish. To test whether the gtshβ promoter-driven GFP may serve as a readout signal of the tubular development, we have treated the embryos with retinoic acid signaing (RA) reagents, in which exogenous RA addition results in a distal extension of the proximal segments, while RA inhibition induces a weakness and shortness of the proximal segments. Therefore, this transgenic line provides a useful tool for genetic or chemical analysis of kidney tubule. PMID:24905828

Modified tubularized incised plate urethroplasty reduces the risk of fistula and meatal stenosis for proximal hypospadias: a report of 63 cases.

PubMed

Arshadi, Hamid; Sabetkish, Shabnam; Kajbafzadeh, Abdol-Mohammad

2017-12-01

To report the feasibility of modified tubularized incised plate (TIP) urethroplasty technique for proximal hypospadias in 63 cases. From January 2004 to March 2010, 63 patients underwent one-stage TIP urethroplasty (modified Snodgrass technique repair) using 2-3 of three covering layers (corpus spongiosum, dartos, and tunica vaginalis). The primary meatus was proximal penile, penoscrotal, scrotal, and perineal in 38, 13, 10, and 2 patients, respectively. All patients had chordee that was corrected with dorsal plication. Glanuloplasty was performed in all cases. Complications and cosmetic results were documented after 6-72 months of follow-up. A total of 63 boys with proximal hypospadias underwent Snodgrass hypospadias repair at a mean age of 8.5 months (range 6-54). Mean operative time was 210 ± 35 min. Patients were followed up with 6-month intervals for up to 6 years postoperatively. After 6 years of follow-up, nine urethrocutaneous fistulae, four bleeding, four meatal stenoses, and one urethral stricture were reported. Cosmetic result was satisfactory according to parent's opinion and another surgeon. No residual chordee was observed in any cases (without artificial correction). In conclusion, this preliminary report can be estimated as an alternative technique with acceptable complication and cosmetic results for proximal hypospadias correction.

Xenon treatment attenuates early renal allograft injury associated with prolonged hypothermic storage in rats.

PubMed

Zhao, Hailin; Yoshida, Akira; Xiao, Wei; Ologunde, Rele; O'Dea, Kieran P; Takata, Masao; Tralau-Stewart, Catherine; George, Andrew J T; Ma, Daqing

2013-10-01

Prolonged hypothermic storage elicits severe ischemia-reperfusion injury (IRI) to renal grafts, contributing to delayed graft function (DGF) and episodes of acute immune rejection and shortened graft survival. Organoprotective strategies are therefore needed for improving long-term transplant outcome. The aim of this study is to investigate the renoprotective effect of xenon on early allograft injury associated with prolonged hypothermic storage. Xenon exposure enhanced the expression of heat-shock protein 70 (HSP-70) and heme oxygenase 1 (HO-1) and promoted cell survival after hypothermia-hypoxia insult in human proximal tubular (HK-2) cells, which was abolished by HSP-70 or HO-1 siRNA. In the brown Norway to Lewis rat renal transplantation, xenon administered to donor or recipient decreased the renal tubular cell death, inflammation, and MHC II expression, while delayed graft function (DGF) was therefore reduced. Pathological changes associated with acute rejection, including T-cell, macrophage, and fibroblast infiltration, were also decreased with xenon treatment. Donors or recipients treated with xenon in combination with cyclosporin A had prolonged renal allograft survival. Xenon protects allografts against delayed graft function, attenuates acute immune rejection, and enhances graft survival after prolonged hypothermic storage. Furthermore, xenon works additively with cyclosporin A to preserve post-transplant renal function.

Proximal renal tubular acidosis

MedlinePlus

... Tests The health care provider will perform a physical exam and ask about the symptoms. Tests that may be ordered include: Arterial blood gas Blood chemistry Blood pH level Urine pH and acid-loading ...

Expression of cleaved caspase-3 in renal tubular cells in Plasmodium falciparum malaria patients.

PubMed

Wichapoon, Benjamas; Punsawad, Chuchard; Viriyavejakul, Parnpen

2017-01-01

In Plasmodium falciparum malaria, the clinical manifestation of acute kidney injury (AKI) is commonly associated with acute tubular necrosis (ATN) in the kidney tissues. Renal tubular cells often exhibit various degrees of cloudy swelling, cell degeneration, and frank necrosis. To study individual cell death, this study evaluates the degree of renal tubular necrosis in association with apoptosis in malarial kidneys. Kidney tissues from P. falciparum malaria with AKI (10 cases), and without AKI (10 cases) were evaluated for tubular pathology. Normal kidney tissues from 10 cases served as controls. Tubular necrosis was assessed quantitatively in kidney tissues infected with P. falciparum malaria, based on histopathological evaluation. In addition, the occurrence of apoptosis was investigated using cleaved caspase-3 marker. Correlation between tubular necrosis and apoptosis was analyzed. Tubular necrosis was found to be highest in P. falciparum malaria patients with AKI (36.44% ± 3.21), compared to non-AKI (15.88% ± 1.63) and control groups (2.58% ± 0.39) (all p < 0.001). In the AKI group, the distal tubules showed a significantly higher degree of tubular necrosis than the proximal tubules (p = 0.021) and collecting tubules (p = 0.033). Tubular necrosis was significantly correlated with the level of serum creatinine (r = 0.596, p = 0.006), and the occurrence of apoptosis (r = 0.681, p = 0.001). In malarial AKI, the process of apoptosis occurs in ATN. © 2016 Asian Pacific Society of Nephrology.

Transient renal tubulopathy in a racing Greyhound.

PubMed

Abraham, L A; Tyrrell, D; Charles, J A

2006-11-01

A 2-year-old female Greyhound was presented for inappetence and lethargy. On referral, results of diagnostic tests indicated renal glucosuria, increased excretion of selected amino acids and abnormal fractional excretion of electrolytes consistent with renal tubular dysfunction. Systemic blood pressure was elevated. Renal biopsy revealed mild proximal renal tubular damage consistent with a subacute toxic or hypoxic insult. Systemic hypertension, renal glucosuria and altered fractional excretion of electrolytes resolved during the 7 day period of hospital treatment. The Greyhound resumed training without recurrence of renal dysfunction.

Tamm-Horsfall Protein Regulates Granulopoiesis and Systemic Neutrophil Homeostasis

PubMed Central

Micanovic, Radmila; Chitteti, Brahmananda R.; Dagher, Pierre C.; Srour, Edward F.; Khan, Shehnaz; Hato, Takashi; Lyle, Allison; Tong, Yan; Wu, Xue-Ru

2015-01-01

Tamm-Horsfall protein (THP) is a glycoprotein uniquely expressed in the kidney. We recently showed an important role for THP in mediating tubular cross-talk in the outer medulla and in suppressing neutrophil infiltration after kidney injury. However, it remains unclear whether THP has a broader role in neutrophil homeostasis. In this study, we show that THP deficiency in mice increases the number of neutrophils, not only in the kidney but also in the circulation and in the liver, through enhanced granulopoiesis in the bone marrow. Using multiplex ELISA, we identified IL-17 as a key granulopoietic cytokine specifically upregulated in the kidneys but not in the liver of THP−/− mice. Indeed, neutralization of IL-17 in THP−/− mice completely reversed the systemic neutrophilia. Furthermore, IL-23 was also elevated in THP−/− kidneys. We performed real-time PCR on laser microdissected tubular segments and FACS-sorted renal immune cells and identified the S3 proximal segments, but not renal macrophages, as a major source of increased IL-23 synthesis. In conclusion, we show that THP deficiency stimulates proximal epithelial activation of the IL-23/IL-17 axis and systemic neutrophilia. Our findings provide evidence that the kidney epithelium in the outer medulla can regulate granulopoiesis. When this novel function is added to its known role in erythropoiesis, the kidney emerges as an important regulator of the hematopoietic system. PMID:25556169

Renal function in urinary schistosomiasis in the Natal Province of South Africa.

PubMed

Coopan, R M; Naidoo, K; Jialal, I

1987-11-01

Renal function was assessed in 101 schoolchildren with active urinary schistosomiasis by measuring serum creatinine, urate, urea, and B2-microglobulin, urinary B2 microglobulin, and the glomerular filtration rate. Glomerular function in all subjects was normal as were serum creatinine, urate, and urea levels. Serum B2-microglobulin was elevated in only 8% of subjects while urinary B2-microglobulin only was raised in 7% of subjects, indicating proximal tubular dysfunction, a previously unreported feature in urinary schistosomiasis. Urinary tract abnormalities were found in 43% of subjects consenting to an excretory urogram but no correlation with biochemical parameters of renal function was noted. Serum angiotensin converting enzyme level measured in 70 subjects was elevated in 11% of subjects and was regarded as a possible measure of increased granulomatous activity.

Effects of autophagy and endocytosis on the activity of matrix metalloproteinase‑2 in human renal proximal tubular cells under hypoxia.

PubMed

Yu, Wenmin; Wang, Zhi; Li, Yiping; Liu, Lei; Liu, Jing; Ding, Fenggan; Zhang, Xiaoyi; Cheng, Zhengyuan; Chen, Pingsheng

2017-05-01

Tubulointerstitial fibrosis is characterized by tubular atrophy with basement membrane thickening and accumulation of interstitial extracellular matrix (ECM). A decrease in the activity of matrix metalloproteinase‑2 (MMP‑2) may promote this process. Although proximal tubular cells are sensitive to oxygen deprivation, whether cellular autophagy or endocytosis induced by hypoxia can alter the activity of MMP‑2 remains to be elucidated. The aim of the present study was to investigate whether autophagy and endocytosis induced by hypoxia can have an effect on the activity of MMP‑2 in HK‑2 cells. The investigations involved exposing the HK‑2 cell line to an autophagy inhibitor, 3‑MA, or an endocytotic inhibitor, filipin. The mRNA expression of MMP‑2 was elevated in the hypoxic milieu. Furthermore, it was found that filipin increased the activity of MMP‑2 under hypoxia. These results suggested that autophagy and endocytosis were potential mediators for the altered expression of MMP‑2, and endocytosis was a potential target for regulating the activity of MMP‑2. These data suggested that hypoxia may be an important pro‑fibrogenic stimulus, which acts in part via endocytosis.

A case report of nephrogenic diabetes insipidus with idiopathic Fanconi syndrome in a child who presented with vitamin D resistant rickets.

PubMed

Patra, Soumya; Nadri, Gulnaz; Chowdhary, Harish; Pemde, Harish K; Singh, Varinder; Chandra, Jagdish

2014-05-01

Fanconi syndrome is a complex of multiple tubular dysfunctions of proximal tubular cells, occurring alone or in association with a variety of inherited (primary) or acquired (secondary) disorders. It is characterized by aminoaciduria, normoglycemic glycosuria, tubular proteinuria without hematuria, metabolic acidosis without anion gap and excessive urinary excretion of phosphorous, calcium, uric acid, bicarbonate, sodium, potassium and magnesium. Diabetes insipidus is a disease of collecting tubules and children mainly present with dehydration and hypernatremia. We are reporting the first case of idiopathic Fanconi's syndrome along with nephrogenic diabetes insipidus in a child who presented to us with vitamin D resistant rickets. Medline search did not reveal any case of nephrogenic diabetes insipidus (NDI) associated with idiopathic Fanconi syndrome. We hypothesized that the NDI may be due to to severe hypokalemia induced tubular dysfunction.

Nephrogenic diabetes insipidus with idiopathic Fanconi's syndrome in a child who presented as vitamin D resistant rickets.

PubMed

Patra, Soumya; Nadri, Gulnaz; Chowdhary, Harish; Pemde, Harish K; Singh, Varinder; Chandra, Jagdish

2011-10-01

Fanconi's syndrome is a complex of multiple tubular dysfunctions of proximal tubular cells occurring alone or in association with a variety of inherited (primary) or acquired (secondary) disorders. It is characterized by aminoaciduria, normoglycaemic glycosuria, tubular proteinuria without hematuria, metabolic acidosis without anion gap and excessive urinary excretion of phosphorous, calcium, uric acid, bicarbonate, sodium, potassium, and magnesium. Whereas diabetes insipidus is a disease of collecting tubules and child mainly presents with dehydration and hypernatremia. Though all the cases published till date were secondary to drugs, myeloma, hematological disorders, etc., we are reporting the first case of idiopathic Fanconi's syndrome along with nephrogenic diabetes insipidus in a child who presented to us as resistant rickets. Medline search did not reveal any case of nephrogenic diabetes insipidus associated with idiopathic Fanconi syndrome. We hypothesized that the NDI may be due to of severe hypokalemia induced tubular dysfunction.

An intracellular matrix metalloproteinase-2 isoform induces tubular regulated necrosis: implications for acute kidney injury.

PubMed

Ceron, Carla S; Baligand, Celine; Joshi, Sunil; Wanga, Shaynah; Cowley, Patrick M; Walker, Joy P; Song, Sang Heon; Mahimkar, Rajeev; Baker, Anthony J; Raffai, Robert L; Wang, Zhen J; Lovett, David H

2017-06-01

Acute kidney injury (AKI) causes severe morbidity, mortality, and chronic kidney disease (CKD). Mortality is particularly marked in the elderly and with preexisting CKD. Oxidative stress is a common theme in models of AKI induced by ischemia-reperfusion (I-R) injury. We recently characterized an intracellular isoform of matrix metalloproteinase-2 (MMP-2) induced by oxidative stress-mediated activation of an alternate promoter in the first intron of the MMP-2 gene. This generates an NH 2 -terminal truncated MMP-2 (NTT-MMP-2) isoform that is intracellular and associated with mitochondria. The NTT-MMP-2 isoform is expressed in kidneys of 14-mo-old mice and in a mouse model of coronary atherosclerosis and heart failure with CKD. We recently determined that NTT-MMP-2 is induced in human renal transplants with delayed graft function and correlated with tubular cell necrosis. To determine mechanism(s) of action, we generated proximal tubule cell-specific NTT-MMP-2 transgenic mice. Although morphologically normal at the light microscopic level at 4 mo, ultrastructural studies revealed foci of tubular epithelial cell necrosis, the mitochondrial permeability transition, and mitophagy. To determine whether NTT-MMP-2 expression enhances sensitivity to I-R injury, we performed unilateral I-R to induce mild tubular injury in wild-type mice. In contrast, expression of the NTT-MMP-2 isoform resulted in a dramatic increase in tubular cell necrosis, inflammation, and fibrosis. NTT-MMP-2 mice had enhanced expression of innate immunity genes and release of danger-associated molecular pattern molecules. We conclude that NTT-MMP-2 "primes" the kidney to enhanced susceptibility to I-R injury via induction of mitochondrial dysfunction. NTT-MMP-2 may be a novel AKI treatment target.

Mechanism of cisplatin proximal tubule toxicity revealed by integrating transcriptomics, proteomics, metabolomics and biokinetics.

PubMed

Wilmes, Anja; Bielow, Chris; Ranninger, Christina; Bellwon, Patricia; Aschauer, Lydia; Limonciel, Alice; Chassaigne, Hubert; Kristl, Theresa; Aiche, Stephan; Huber, Christian G; Guillou, Claude; Hewitt, Philipp; Leonard, Martin O; Dekant, Wolfgang; Bois, Frederic; Jennings, Paul

2015-12-25

Cisplatin is one of the most widely used chemotherapeutic agents for the treatment of solid tumours. The major dose-limiting factor is nephrotoxicity, in particular in the proximal tubule. Here, we use an integrated omics approach, including transcriptomics, proteomics and metabolomics coupled to biokinetics to identify cell stress response pathways induced by cisplatin. The human renal proximal tubular cell line RPTEC/TERT1 was treated with sub-cytotoxic concentrations of cisplatin (0.5 and 2 μM) in a daily repeat dose treating regime for up to 14 days. Biokinetic analysis showed that cisplatin was taken up from the basolateral compartment, transported to the apical compartment, and accumulated in cells over time. This is in line with basolateral uptake of cisplatin via organic cation transporter 2 and bioactivation via gamma-glutamyl transpeptidase located on the apical side of proximal tubular cells. Cisplatin affected several pathways including, p53 signalling, Nrf2 mediated oxidative stress response, mitochondrial processes, mTOR and AMPK signalling. In addition, we identified novel pathways changed by cisplatin, including eIF2 signalling, actin nucleation via the ARP/WASP complex and regulation of cell polarization. In conclusion, using an integrated omic approach together with biokinetics we have identified both novel and established mechanisms of cisplatin toxicity. Copyright © 2014 Elsevier Ltd. All rights reserved.

Low molecular weight fucoidan protects renal tubular cells from injury induced by albumin overload.

PubMed

Jia, Yingli; Sun, Yi; Weng, Lin; Li, Yingjie; Zhang, Quanbin; Zhou, Hong; Yang, Baoxue

2016-08-22

Albuminuria is a causative and aggravating factor for progressive renal damage in chronic kidney disease (CKD). The aim of this study was to determine if low molecular weight fucoidan (LMWF) could protect renal function and tubular cells from albumin overload caused injury. Treatment with 10 mg/g bovine serum albumin caused renal dysfunction, morphological changes, and overexpression of inflammation and fibrosis associated proteins in 129S2/Sv mice. LMWF (100 mg/kg) protected against kidney injury and renal dysfunction with decreased blood creatinine by 34% and urea nitrogen by 25%, increased creatinine clearance by 48%, and decreased significantly urinary albumin concentration. In vitro proximal tubule epithelial cell (NRK-52E) model showed that LMWF dose-dependently inhibited overexpression of proinflammatory and profibrotic factors, oxidative stress and apoptosis caused by albumin overload. These experimental results indicate that LMWF protects against albumin overload caused renal injury by inhibiting inflammation, fibrosis, oxidative stress and apoptosis, which suggests that LMWF could be a promising candidate drug for preventing CKD.

GW501516, a PPARδ agonist, ameliorates tubulointerstitial inflammation in proteinuric kidney disease via inhibition of TAK1-NFκB pathway in mice.

PubMed

Yang, Xu; Kume, Shinji; Tanaka, Yuki; Isshiki, Keiji; Araki, Shin-ichi; Chin-Kanasaki, Masami; Sugimoto, Toshiro; Koya, Daisuke; Haneda, Masakazu; Sugaya, Takeshi; Li, Detian; Han, Ping; Nishio, Yoshihiko; Kashiwagi, Atsunori; Maegawa, Hiroshi; Uzu, Takashi

2011-01-01

Peroxisome proliferator-activated receptors (PPARs) are a nuclear receptor family of ligand-inducible transcription factors, which have three different isoforms: PPARα, δ and γ. It has been demonstrated that PPARα and γ agonists have renoprotective effects in proteinuric kidney diseases; however, the role of PPARδ agonists in kidney diseases remains unclear. Thus, we examined the renoprotective effect of GW501516, a PPARδ agonist, in a protein-overload mouse nephropathy model and identified its molecular mechanism. Mice fed with a control diet or GW501516-containing diet were intraperitoneally injected with free fatty acid (FFA)-bound albumin or PBS(-). In the control group, protein overload caused tubular damages, macrophage infiltration and increased mRNA expression of MCP-1 and TNFα. These effects were prevented by GW501516 treatment. In proteinuric kidney diseases, excess exposure of proximal tubular cells to albumin, FFA bound to albumin or cytokines such as TNFα is detrimental. In vitro studies using cultured proximal tubular cells showed that GW501516 attenuated both TNFα- and FFA (palmitate)-induced, but not albumin-induced, MCP-1 expression via direct inhibition of the TGF-β activated kinase 1 (TAK1)-NFκB pathway, a common downstream signaling pathway to TNFα receptor and toll-like receptor-4. In conclusion, we demonstrate that GW501516 has an anti-inflammatory effect in renal tubular cells and may serve as a therapeutic candidate to attenuate tubulointerstitial lesions in proteinuric kidney diseases.

GW501516, a PPARδ Agonist, Ameliorates Tubulointerstitial Inflammation in Proteinuric Kidney Disease via Inhibition of TAK1-NFκB Pathway in Mice

PubMed Central

Yang, Xu; Kume, Shinji; Tanaka, Yuki; Isshiki, Keiji; Araki, Shin-ichi; Chin-Kanasaki, Masami; Sugimoto, Toshiro; Koya, Daisuke; Haneda, Masakazu; Sugaya, Takeshi; Li, Detian; Han, Ping; Nishio, Yoshihiko; Kashiwagi, Atsunori; Maegawa, Hiroshi; Uzu, Takashi

2011-01-01

Peroxisome proliferator-activated receptors (PPARs) are a nuclear receptor family of ligand-inducible transcription factors, which have three different isoforms: PPARα, δ and γ. It has been demonstrated that PPARα and γ agonists have renoprotective effects in proteinuric kidney diseases; however, the role of PPARδ agonists in kidney diseases remains unclear. Thus, we examined the renoprotective effect of GW501516, a PPARδ agonist, in a protein-overload mouse nephropathy model and identified its molecular mechanism. Mice fed with a control diet or GW501516-containing diet were intraperitoneally injected with free fatty acid (FFA)-bound albumin or PBS(−). In the control group, protein overload caused tubular damages, macrophage infiltration and increased mRNA expression of MCP-1 and TNFα. These effects were prevented by GW501516 treatment. In proteinuric kidney diseases, excess exposure of proximal tubular cells to albumin, FFA bound to albumin or cytokines such as TNFα is detrimental. In vitro studies using cultured proximal tubular cells showed that GW501516 attenuated both TNFα- and FFA (palmitate)-induced, but not albumin-induced, MCP-1 expression via direct inhibition of the TGF-β activated kinase 1 (TAK1)-NFκB pathway, a common downstream signaling pathway to TNFα receptor and toll-like receptor-4. In conclusion, we demonstrate that GW501516 has an anti-inflammatory effect in renal tubular cells and may serve as a therapeutic candidate to attenuate tubulointerstitial lesions in proteinuric kidney diseases. PMID:21966476

Fanconi syndrome and severe polyuria: an uncommon clinicobiological presentation of a Gitelman syndrome.

PubMed

Bouchireb, Karim; Boyer, Olivia; Mansour-Hendili, Lamisse; Garnier, Arnaud; Heidet, Laurence; Niaudet, Patrick; Salomon, Remi; Poussou, Rosa Vargas

2014-08-11

Gitelman syndrome is an autosomal recessive tubulopathy characterized by hypokalemia, hypomagnesemia, metabolic alkalosis and hypocalciuria. The majority of patients do not present with symptoms until late childhood or adulthood, and the symptoms are generally mild. We report here the first case of Gitelman syndrome presenting with the biological features of Fanconi syndrome and an early polyuria since the neonatal period. We discuss in this article the atypical electrolytes losses found in our patient, as well as the possible mechanisms of severe polyuria. A 6-year-old Caucasian girl was admitted via the Emergency department for vomiting, and initial laboratory investigations found hyponatremia, hypokalemia, metabolic acidosis with normal anion gap, hypophosphatemia, and hypouricemia. Urinalysis revealed Na, K, Ph and uric acid losses. Thus, the initial biological profile was in favor of a proximal tubular defect. However, etiological investigations were inconclusive and the patient was discharged with potassium chloride and phosphorus supplementation. Three weeks later, further laboratory analysis indicated persistent hypokalemia, a metabolic alkalosis, hypomagnesemia, and hypocalciuria. We therefore sequenced the SLC12A3 gene and found a compound heterozygosity for 2 known missense mutations. Gitelman syndrome can have varying and sometimes atypical presentations, and should be suspected in case of hypokalemic tubular disorders that do not belong to any obvious syndromic entity. In this case, the proximal tubular dysfunction could be secondary to the severe hypokalemia. This report emphasizes the need for clinicians to repeat laboratory tests in undiagnosed tubular disorders, especially not during decompensation episodes.

Upregulation of TLR4 via PKC activation contributes to impaired wound healing in high-glucose-treated kidney proximal tubular cells.

PubMed

Peng, Jianping; Zheng, Hang; Wang, Xia; Cheng, Zhixiang

2017-01-01

Acute kidney injury (AKI) leads to a worse prognosis in diabetic patients compared with prognoses in non-diabetic patients, but whether and how diabetes affects kidney repair after AKI remains unknown. Here, we used scratch-wound healing and transwell migration models to examine whether and how wound healing is affected by high glucose levels in cultured kidney proximal tubular cells (RPTC). The results show that scratch-wound healing and transwell migration were significantly slower in high-glucose-treated kidney tubular cells (30 mM glucose) than in low-glucose-treated cells (5.5 mM). Toll-like receptor 4 (TLR4), MyD88, phospho-protein kinase C (PKC), phospho-p38 MAPK and monocyte chemoattractant protein-1 (MCP-1) mRNA levels were upregulated after high glucose treatments. Staurosporine, a selective PKC inhibitor, inhibited TLR4, MyD88 and p-p38 upregulation in the high-glucose-treated cells, indicating the involvement of PKC in high-glucose-induced TLR4 upregulation. The pharmacological inhibition of TLR4 or shRNA-mediated TLR4 knockdown improved wound healing and transwell migration in high-glucose-treated RPTC. In contrast, the overexpression of TLR4 in low-glucose-treated RPTC suppressed wound healing, mimicking the effects of high glucose levels. These results suggest that the upregulation of TLR4 expression via PKC activation contributes to defective wound healing in high-glucose-treated kidney tubular cells.

Upregulation of TLR4 via PKC activation contributes to impaired wound healing in high-glucose-treated kidney proximal tubular cells

PubMed Central

Peng, Jianping; Zheng, Hang; Wang, Xia; Cheng, Zhixiang

2017-01-01

Acute kidney injury (AKI) leads to a worse prognosis in diabetic patients compared with prognoses in non-diabetic patients, but whether and how diabetes affects kidney repair after AKI remains unknown. Here, we used scratch-wound healing and transwell migration models to examine whether and how wound healing is affected by high glucose levels in cultured kidney proximal tubular cells (RPTC). The results show that scratch-wound healing and transwell migration were significantly slower in high-glucose-treated kidney tubular cells (30 mM glucose) than in low-glucose-treated cells (5.5 mM). Toll-like receptor 4 (TLR4), MyD88, phospho-protein kinase C (PKC), phospho-p38 MAPK and monocyte chemoattractant protein-1 (MCP-1) mRNA levels were upregulated after high glucose treatments. Staurosporine, a selective PKC inhibitor, inhibited TLR4, MyD88 and p-p38 upregulation in the high-glucose-treated cells, indicating the involvement of PKC in high-glucose-induced TLR4 upregulation. The pharmacological inhibition of TLR4 or shRNA-mediated TLR4 knockdown improved wound healing and transwell migration in high-glucose-treated RPTC. In contrast, the overexpression of TLR4 in low-glucose-treated RPTC suppressed wound healing, mimicking the effects of high glucose levels. These results suggest that the upregulation of TLR4 expression via PKC activation contributes to defective wound healing in high-glucose-treated kidney tubular cells. PMID:28542370

Ultrastructural study of electron dense deposits in renal tubular basement membrane: prevalence and relationship to epithelial atrophy.

PubMed

Yong, Jim L C; Killingsworth, Murray C

2014-08-01

This study reports the prevalence of immune deposits associated with the proximal and distal tubules in a series of routine renal biopsies received in our department during a single calendar year. From 87 cases, 65 (74%) were found to have glomerular immune deposits by immunofluorescence. Tubular immune deposits were found in 12 cases (18%), 3 of which had no glomerular deposits. By transmission electron microscopy (EM), 58 cases (66%) were found to have deposits of granular or vesicular material associated with the tubular basement membranes (TBM). Finely granular electron dense deposits appeared to correspond to the immune deposits seen by immunofluorescence microscopy (IF) and may be a sensitive marker of immune deposition.

Ultrastructural Study of Electron Dense Deposits in Renal Tubular Basement Membrane: Prevalence and Relationship to Epithelial Atrophy

PubMed Central

Killingsworth, Murray C.

2014-01-01

This study reports the prevalence of immune deposits associated with the proximal and distal tubules in a series of routine renal biopsies received in our department during a single calendar year. From 87 cases, 65 (74%) were found to have glomerular immune deposits by immunofluorescence. Tubular immune deposits were found in 12 cases (18%), 3 of which had no glomerular deposits. By transmission electron microscopy (EM), 58 cases (66%) were found to have deposits of granular or vesicular material associated with the tubular basement membranes (TBM). Finely granular electron dense deposits appeared to correspond to the immune deposits seen by immunofluorescence microscopy (IF) and may be a sensitive marker of immune deposition. PMID:24933115

RADIATION FACILITY FOR NUCLEAR REACTORS

DOEpatents

Currier, E.L. Jr.; Nicklas, J.H.

1961-12-12

A radiation facility is designed for irradiating samples in close proximity to the core of a nuclear reactor. The facility comprises essentially a tubular member extending through the biological shield of the reactor and containing a manipulatable rod having the sample carrier at its inner end, the carrier being longitudinally movable from a position in close proximity to the reactor core to a position between the inner and outer faces of the shield. Shield plugs are provided within the tubular member to prevent direct radiation from the core emanating therethrough. In this device, samples may be inserted or removed during normal operation of the reactor without exposing personnel to direct radiation from the reactor core. A storage chamber is also provided within the radiation facility to contain an irradiated sample during the period of time required to reduce the radioactivity enough to permit removal of the sample for external handling. (AEC)

Perigraft Plug Embolization of the Internal Iliac Artery and Implantation of a Bifurcated Stentgraft: One Treatment Option for Insufficient Tubular Stentgraft Repair of a Common Iliac Artery Aneurysm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goltz, Jan Peter, E-mail: janpeter.goltz@uksh.de; Loesaus, Julia; Frydrychowicz, Alex

We report an endovascular technique for the treatment of type Ia endoleak after a plain tubular stentgraft had been implanted for a large common iliac artery aneurysm with an insufficient proximal landing zone and without occlusion of the hypogastric in another hospital. CT follow-up showed an endoleak with continuous sac expansion over 12 months. This was classified as type Ia by means of dynamic contrast-enhanced MRI. Before a bifurcated stentgraft was implanted to relocate the landing zone more proximally, the still perfused ipsilateral hypogastric artery was embolized to prevent a type II endoleak. A guidewire was manipulated alongside the indwelling stentgraft.more » The internal iliac artery could then be selectively intubated followed by successful plug embolization of the vessel’s orifice despite the stentgraft being in place.« less

Apoptosis of rat renal cells by organophosphate pesticide, quinalphos: Ultrastructural study.

PubMed

Eid, Refaat A

2017-01-01

Quinalphos or Ekalux, an organophosphate pesticide, is used in controlling the pests of a variety of crops. Quinalphos was studied on male Sprague-Dawley albino rats. The acute po LD50 of technical Ekalux was 19.95 mg/kg in males. Ekalux, produced several pathological changes in the kidney. A glomerulus demonstrated capillary lumina occluded by degenerated cellular debris. Basement membrane showed irregular wrinkling and branching. The proximal tubular cells showed damage such as dilation of endoplasmic reticulum, accumulation of glycogen granules, and pyknotic nucleus. The changes also included swelling of the mitochondria and reduction of the cristae up to total destruction. The distal tubular changes included electron lucency and vacuolation of cytoplasm. The distal convoluted tubule wall showed edematous epithelial cells, formation of blebs, and microvilli loss. These results suggest that subchronic exposure of rats to Ekalux causes ultrastructural changes in renal corpuscle and marked ultrastructural changes in proximal and distal tubules.

Perigraft Plug Embolization of the Internal Iliac Artery and Implantation of a Bifurcated Stentgraft: One Treatment Option for Insufficient Tubular Stentgraft Repair of a Common Iliac Artery Aneurysm.

PubMed

Goltz, Jan Peter; Loesaus, Julia; Frydrychowicz, Alex; Barkhausen, Jörg; Wiedner, Marcus

2016-02-01

We report an endovascular technique for the treatment of type Ia endoleak after a plain tubular stentgraft had been implanted for a large common iliac artery aneurysm with an insufficient proximal landing zone and without occlusion of the hypogastric in another hospital. CT follow-up showed an endoleak with continuous sac expansion over 12 months. This was classified as type Ia by means of dynamic contrast-enhanced MRI. Before a bifurcated stentgraft was implanted to relocate the landing zone more proximally, the still perfused ipsilateral hypogastric artery was embolized to prevent a type II endoleak. A guidewire was manipulated alongside the indwelling stentgraft. The internal iliac artery could then be selectively intubated followed by successful plug embolization of the vessel's orifice despite the stentgraft being in place.

Physiological roles of claudins in kidney tubule paracellular transport.

PubMed

Muto, Shigeaki

2017-01-01

The paracellular pathways in renal tubular epithelia such as the proximal tubules, which reabsorb the largest fraction of filtered solutes and water and are leaky epithelia, are important routes for transepithelial transport of solutes and water. Movement occurs passively via an extracellular route through the tight junction between cells. The characteristics of paracellular transport vary among different nephron segments with leaky or tighter epithelia. Claudins expressed at tight junctions form pores and barriers for paracellular transport. Claudins are from a multigene family, comprising at least 27 members in mammals. Multiple claudins are expressed at tight junctions of individual nephron segments in a nephron segment-specific manner. Over the last decade, there have been advances in our understanding of the structure and functions of claudins. This paper is a review of our current knowledge of claudins, with special emphasis on their physiological roles in proximal tubule paracellular solute and water transport. Copyright © 2017 the American Physiological Society.

The role of renal proximal tubule P450 enzymes in chloroform-induced nephrotoxicity: Utility of renal specific P450 reductase knockout mouse models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Senyan; Wadsworth Center, New York State Department of Health, and School of Public Health, State University of New York, Albany, NY 12201; Yao, Yunyi

The kidney is a primary target for numerous toxic compounds. Cytochrome P450 enzymes (P450) are responsible for the metabolic activation of various chemical compounds, and in the kidney are predominantly expressed in proximal tubules. The aim of this study was to test the hypothesis that renal proximal tubular P450s are critical for nephrotoxicity caused by chemicals such as chloroform. We developed two new mouse models, one having proximal tubule-specific deletion of the cytochrome P450 reductase (Cpr) gene (the enzyme required for all microsomal P450 activities), designated proximal tubule-Cpr-null (PTCN), and the other having proximal tubule-specific rescue of CPR activity withmore » the global suppression of CPR activity in all extra-proximal tubular tissues, designated extra-proximal tubule-Cpr-low (XPT-CL). The PTCN, XPT-CL, Cpr-low (CL), and wild-type (WT) mice were treated with a single oral dose of chloroform at 200 mg/kg. Blood, liver and kidney samples were obtained at 24 h after the treatment. Renal toxicity was assessed by measuring BUN and creatinine levels, and by pathological examination. The blood and tissue levels of chloroform were determined. The severity of toxicity was less in PTCN and CL mice, compared with that of WT and XPT-CL mice. There were no significant differences in chloroform levels in the blood, liver, or kidney, between PTCN and WT mice, or between XPT-CL and CL mice. These findings indicate that local P450-dependent activities play an important role in the nephrotoxicity induced by chloroform. Our results also demonstrate the usefulness of these novel mouse models for studies of chemical-induced kidney toxicity. - Highlights: • New mouse models were developed with varying P450 activities in the proximal tubule. • These mouse models were treated with chloroform, a nephrotoxicant. • Studies showed the importance of local P450s in chloroform-induced nephrotoxicity.« less

Albumin-induced apoptosis of tubular cells is modulated by BASP1

PubMed Central

Sanchez-Niño, M D; Fernandez-Fernandez, B; Perez-Gomez, M V; Poveda, J; Sanz, A B; Cannata-Ortiz, P; Ruiz-Ortega, M; Egido, J; Selgas, R; Ortiz, A

2015-01-01

Albuminuria promotes tubular injury and cell death, and is associated with faster progression of chronic kidney disease (CKD) to end-stage renal disease. However, the molecular mechanisms regulating tubular cell death in response to albuminuria are not fully understood. Brain abundant signal protein 1 (BASP1) was recently shown to mediate glucose-induced apoptosis in tubular cells. We have studied the role of BASP1 in albumin-induced tubular cell death. BASP1 expression was studied in experimental puromycin aminonucleoside-induced nephrotic syndrome in rats and in human nephrotic syndrome. The role of BASP1 in albumin-induced apoptosis was studied in cultured human HK2 proximal tubular epithelial cells. Puromycin aminonucleoside induced proteinuria and increased total kidney BASP1 mRNA and protein expression. Immunohistochemistry localized the increased BASP1 to tubular cells. BASP1 expression colocalized with deoxynucleotidyl-transferase-mediated dUTP nick-end labeling staining for apoptotic cells. Increased tubular BASP1 expression was observed in human proteinuric nephropathy by immunohistochemistry, providing evidence for potential clinical relevance. In cultured tubular cells, albumin induced apoptosis and increased BASP1 mRNA and protein expression at 6–48 h. Confocal microscopy localized the increased BASP1 expression in albumin-treated cells mainly to the perinuclear area. A peripheral location near the cell membrane was more conspicuous in albumin-treated apoptotic cells, where it colocalized with actin. Inhibition of BASP1 expression by a BASP1 siRNA protected from albumin-induced apoptosis. In conclusion, albumin-induced apoptosis in tubular cells is BASP1-dependent. This information may be used to design novel therapeutic approaches to slow CKD progression based on protection of tubular cells from the adverse consequences of albuminuria. PMID:25675304

Quantification of single-kidney glomerular filtration rate with electron-beam computed tomography

NASA Astrophysics Data System (ADS)

Lerman, Lilach O.; Ritman, Erik L.; Pelaez, Laura I.; Sheedy, Patrick F., II; Krier, James D.

2000-04-01

The ability to accurately and noninvasively quantify single- kidney GFR could be invaluable for assessment of renal function. We developed a model that enables this measurement with EBCT. To examine the reliability of this method, EBCT renal flow and volume studies after contrast media administration were performed in pigs with unilateral renal artery stenosis (Group 1), controls (Group 2), and simultaneously with inulin clearance (Group 3). Renal flow curves, obtained from the bilateral renal cortex and medulla, depicted transit of the contrast through the vascular and tubular compartments, and were fitted using extended gamma- variate functions. Renal blood flow was calculated as the sum of products of cortical and medullary perfusions and volumes. Normalized GFR (mL/min/cc) was calculated using the rate (maximal slope) of proximal tubular contrast accumulation, and EBCT-GFR as normalized GFR* cortical volume. In Group 1, the decreased GFR of the stenotic kidney correlated well with its decreased volume and RBF, and with the degree of stenosis (r equals -0.99). In Group 3, EBCT-GFR correlated well with inulin clearance (slope 1.1, r equals 0.81). This novel approach can be very useful for quantification of concurrent regional hemodynamics and function in the intact kidneys, in a manner potentially applicable to humans.

The effect of proximal anastomosis on the expansion rate of a dilated ascending aorta in coronary artery bypass surgery: a prospective study

PubMed Central

Balcı, Ahmet Yavuz; Vural, Unsal; Özdemir, MD Fatih; Kızılay, Mehmet; Şenocak, Mutlu; Kayacıoğlu, Ilyas; Yekeler, Ibrahim; Aksoy, Rezan; Satılmış,, Seçkin; Şaşkın, Huseyin

2017-01-01

Summary Background: This study was designed to determine the short- and long-term effects of proximal aortic anastomosis, performed during isolated coronary artery bypass grafting (CABG) in patients with dilatation of the ascending aorta who did not require surgical intervention. Methods: The study was performed on 192 (38 female and 160 male patients; mean age, 62.1 ± 9.2 years; range, 42–80 years) patients with dilatation of the ascending aorta who underwent CABG surgery between 1 June 2006 and 31 May 2014. In group 1 (n = 114), the saphenous vein and left internal mammarian artery grafts were used, and proximal anastomosis was performed on the ascending aorta. In group 2 (n = 78), left and right internal mammarian artery grafts were used, and proximal aortic anastomosis was not performed. Pre-operatively and in the first and third years postoperatively, the ascending aortic diameter was measured and recorded using transthoracic echocardiography at four different regions (annulus, sinus of Valsalva, sinotubular junction and tubular aorta). Results: A statistically significant difference was found between the groups for the number of grafts used and the duration of aortic cross-clamping and cardiopulmonary bypass. No significant intergroup difference was seen for the mean diameter of the ascending aorta (p > 0.05). Annual changes in the aortic diameter were found to be extremely significantly different in both groups (p = 0.0001). Mean values of the aortic diameter at the level of the sinotubular junction and tubular ascending aorta, mean aortic diameters (p = 0.002 and p = 0.0001, respectively), annual increase in diameter (p = 0.0001 and p = 0.0001, respectively), and mean annual difference in diameter (p = 0.0001 and p = 0.0001, respectively) at one and three years postoperatively were statistically significantly different between the groups. Conclusion: In patients with ascending aortic dilatation who did not require surgical intervention and who had proximal anastomosis of the ascending aorta and underwent only CABG, we detected statistically significant increases in the diameter of the sinotubular junction and tubular aorta up to three years postoperatively. PMID:27701487

The effect of proximal anastomosis on the expansion rate of a dilated ascending aorta in coronary artery bypass surgery: a prospective study.

PubMed

Yavuz Balci, Ahmet; Vural, Unsal; Aksoy, Rezan; Özdemir, M Fatih; Satilmiş, Seçkin; Kizilay, Mehmet; Şenocak, Mutlu; Şaşkin, Huseyin; Kayacioğlu, Ilyas; Yekeler, Ibrahim

This study was designed to determine the short- and long-term effects of proximal aortic anastomosis, performed during isolated coronary artery bypass grafting (CABG) in patients with dilatation of the ascending aorta who did not require surgical intervention. The study was performed on 192 (38 female and 160 male patients; mean age, 62.1 ± 9.2 years; range, 42-80 years) patients with dilatation of the ascending aorta who underwent CABG surgery between 1 June 2006 and 31 May 2014. In group 1 (n = 114), the saphenous vein and left internal mammarian artery grafts were used, and proximal anastomosis was performed on the ascending aorta. In group 2 (n = 78), left and right internal mammarian artery grafts were used, and proximal aortic anastomosis was not performed. Pre-operatively and in the first and third years postoperatively, the ascending aortic diameter was measured and recorded using transthoracic echocardiography at four different regions (annulus, sinus of Valsalva, sinotubular junction and tubular aorta). A statistically significant difference was found between the groups for the number of grafts used and the duration of aortic cross-clamping and cardiopulmonary bypass. No significant intergroup difference was seen for the mean diameter of the ascending aorta (p > 0.05). Annual changes in the aortic diameter were found to be extremely significantly different in both groups (p = 0.0001). Mean values of the aortic diameter at the level of the sinotubular junction and tubular ascending aorta, mean aortic diameters (p = 0.002 and p = 0.0001, respectively), annual increase in diameter (p = 0.0001 and p = 0.0001, respectively), and mean annual difference in diameter (p = 0.0001 and p = 0.0001, respectively) at one and three years postoperatively were statistically significantly different between the groups. In patients with ascending aortic dilatation who did not require surgical intervention and who had proximal anastomosis of the ascending aorta and underwent only CABG, we detected statistically significant increases in the diameter of the sinotubular junction and tubular aorta up to three years postoperatively.

[Current status of cadmium exposure among Japanese, especially regarding the safety standard for cadmium concentration in rice and adverse effects on proximal renal tubular function observed in farmers exposed to cadmium through consumption of self-grown rice].

PubMed

Horiguchi, Hyogo

2012-01-01

Because the staple food in Japan is rice, which absorbs cadmium (Cd) from the soil efficiently, rice is the main source of exposure to Cd in the Japanese population. In addition, there have been many Cd-contaminated farming areas in Japan. Therefore, a safety standard for the Cd concentration in rice was set as 0.4 ppm by the Japanese government. This safety standard has been followed for decades without any appropriate scientific or legal basis. However, recent epidemiological studies of female Japanese farmers exposed to Cd through self-grown rice, that is, a series of Japanese Multi-centered Environmental Toxicant Study (JMETS), showed evidence that the safety standard is appropriate. Therefore, general Japanese consumers are unlikely exposed to Cd excessively with the application of this safety standard, considering the trend of decreasing amount of rice consumed among the Japanese population. On the other hand, Japanese farmers were found to be at risk of Cd exposure through the consumption of self-grown rice with a high Cd concentration. Actually, the JMETS showed that female farmers at 70 years of age or older had a decreased proximal renal tubular function due to the high renal accumulation of Cd. On the basis of these findings, "medical examinations for Cd exposure" have recently been implemented for farmers residing in Cd-polluted areas in northern Japan. Because it has been estimated that such Cd-polluted areas are actually larger, it is necessary to implement medical examinations of more farmers there, particularly the elderly.

Proximal hypospadias: A persistent challenge. Single institution outcome analysis of three surgical techniques over a 10-year period.

PubMed

Pippi Salle, J L; Sayed, S; Salle, A; Bagli, D; Farhat, W; Koyle, M; Lorenzo, A J

2016-02-01

The optimal treatment of proximal hypospadias remains controversial. Several techniques have been described, but the best approach remains unsettled. To evaluate and compare the complication rates of proximal hypospadias with and without ventral curvature (VC), according to three different surgical techniques: tubularized incised plate (TIP) uretroplasty, dorsal inlay graft TIP (DIG), and staged preputial repair (SR). It was hypothesized that SR performs better than TIP and DIG for proximal hypospadias. Single-center, retrospective chart review of all patients with primary proximal hypospadias reconstructed between 2003 and 2013. The DIG was selectively employed in cases with narrow urethral plate (UP) and deficient spongiosum. Extensive urethral plate (UP) mobilization (UPM), dorsal plication (DP) and/or deep transverse incisions of tunica albuginea (DTITA) were selectively performed when attempting to spare transecting the UP. Division of UP and SR was favored in cases with severe VC (>50°), which was often concurrently managed with DTITA if intrinsic curvature was present. For SR, tubularization of the graft was performed 6 months later. A total of 140 patients were included. Tubularized incised plate (TIP), DIG, and SR techniques were performed in 57, 23, and 60 patients, respectively. The TIP and DIG techniques achieved similar success rates, although DIG was performed in cases of narrow and spongiosum-deficient plates. Reoperation rates with TIP and DIG techniques was 52.6% and 52.1% (NS). Urethro-cutaneous fistulas were seen in 31.5% and 13% of TIP and DIG techniques, respectively. Staged repair accomplished better results than both TIP and DIG techniques, despite being performed in the most unfavorable cases (reoperation rate 28%). After technical modifications, the DIG technique achieved similar outcomes of SR. Proximal hypospadias remains challenging, regardless of the technique utilized for its repair. Urethro-cutaneous fistulas were more commonly seen after long TIP repairs. Approximately half of the patients undergoing long TIP and DIG procedures needed re-intervention, although the percentage decreased significantly with late modifications in the DIG group. Recurrence of VC after TIP and DIG techniques seemed to be a significant and under-reported complication. Staged repairs, despite being performed for the most severe cases, resulted in overall better outcomes. Copyright © 2015 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.

Quantifying Glomerular Permeability of Fluorescent Macromolecules Using 2-Photon Microscopy in Munich Wistar Rats

PubMed Central

Sandoval, Ruben M.; Molitoris, Bruce A.

2013-01-01

Kidney diseases involving urinary loss of large essential macromolecules, such as serum albumin, have long been thought to be caused by alterations in the permeability barrier comprised of podocytes, vascular endothelial cells, and a basement membrane working in unison. Data from our laboratory using intravital 2-photon microscopy revealed a more permeable glomerular filtration barrier (GFB) than previously thought under physiologic conditions, with retrieval of filtered albumin occurring in an early subset of cells called proximal tubule cells (PTC)1,2,3. Previous techniques used to study renal filtration and establishing the characteristic of the filtration barrier involved micropuncture of the lumen of these early tubular segments with sampling of the fluid content and analysis4. These studies determined albumin concentration in the luminal fluid to be virtually non-existent; corresponding closely to what is normally detected in the urine. However, characterization of dextran polymers with defined sizes by this technique revealed those of a size similar to serum albumin had higher levels in the tubular lumen and urine; suggesting increased permeability5. Herein is a detailed outline of the technique used to directly visualize and quantify glomerular fluorescent albumin permeability in vivo. This method allows for detection of filtered albumin across the filtration barrier into Bowman's space (the initial chamber of urinary filtration); and also allows quantification of albumin reabsorption by proximal tubules and visualization of subsequent albumin transcytosis6. The absence of fluorescent albumin along later tubular segments en route to the bladder highlights the efficiency of the retrieval pathway in the earlier proximal tubule segments. Moreover, when this technique was applied to determine permeability of dextrans having a similar size to albumin virtually identical permeability values were reported2. These observations directly support the need to expand the focus of many proteinuric renal diseases to included alterations in proximal tubule cell reclamation. PMID:23628966

Xenon Treatment Protects Against Cold Ischemia Associated Delayed Graft Function and Prolongs Graft Survival in Rats

PubMed Central

Zhao, H; Watts, H R; Chong, M; Huang, H; Tralau-Stewart, C; Maxwell, P H; Maze, M; George, A J T; Ma, D

2013-01-01

Prolonged hypothermic storage causes ischemia-reperfusion injury (IRI) in the renal graft, which is considered to contribute to the occurrence of the delayed graft function (DGF) and chronic graft failure. Strategies are required to protect the graft and to prolong renal graft survival. We demonstrated that xenon exposure to human proximal tubular cells (HK-2) led to activation of range of protective proteins. Xenon treatment prior to or after hypothermia–hypoxia challenge stabilized the HK-2 cellular structure, diminished cytoplasmic translocation of high-mobility group box (HMGB) 1 and suppressed NF-κB activation. In the syngeneic Lewis-to-Lewis rat model of kidney transplantation, xenon exposure to donors before graft retrieval or to recipients after engraftment decreased caspase-3 expression, localized HMGB-1 within nuclei and prevented TLR-4/NF-κB activation in tubular cells; serum pro-inflammatory cytokines IL-1β, IL-6 and TNF-α were reduced and renal function was preserved. Xenon treatment of graft donors or of recipients prolonged renal graft survival following IRI in both Lewis-to-Lewis isografts and Fischer-to-Lewis allografts. Xenon induced cell survival or graft functional recovery was abolished by HIF-1α siRNA. Our data suggest that xenon treatment attenuates DGF and enhances graft survival. This approach could be translated into clinical practice leading to a considerable improvement in long-term graft survival. PMID:23710625

Diuretics and salt transport along the nephron.

PubMed

Bernstein, Paul L; Ellison, David H

2011-11-01

The clinical use of diuretics almost uniformly predated the localization of their site of action. The consequence of diuretic specificity predicts clinical application and side effect, and the proximity of the sodium transporters, one to the next, often dictates potency or diuretic efficiency. All diuretics function by inhibiting the normal transport of sodium from the filtrate into the renal tubular cells. This movement of sodium into the renal epithelial cells on the apical side is facilitated by a series of transporters whose function is, in turn, dependent on the adenosine triphosphate (ATP)-dependent Na-K cotransporter on the basolateral side of the cell. Our growing understanding of the physiology of sodium transport has spawned new possibilities for diuretic development. Copyright © 2011 Elsevier Inc. All rights reserved.

Factor h and properdin recognize different epitopes on renal tubular epithelial heparan sulfate.

PubMed

Zaferani, Azadeh; Vivès, Romain R; van der Pol, Pieter; Navis, Gerjan J; Daha, Mohamed R; van Kooten, Cees; Lortat-Jacob, Hugues; Seelen, Marc A; van den Born, Jacob

2012-09-07

During proteinuria, renal tubular epithelial cells become exposed to ultrafiltrate-derived serum proteins, including complement factors. Recently, we showed that properdin binds to tubular heparan sulfates (HS). We now document that factor H also binds to tubular HS, although to a different epitope than properdin. Factor H was present on the urinary side of renal tubular cells in proteinuric, but not in normal renal tissues and colocalized with properdin in proteinuric kidneys. Factor H dose-dependently bound to proximal tubular epithelial cells (PTEC) in vitro. Preincubation of factor H with exogenous heparin and pretreatment of PTECs with heparitinase abolished the binding to PTECs. Surface plasmon resonance experiments showed high affinity of factor H for heparin and HS (K(D) values of 32 and 93 nm, respectively). Using a library of HS-like polysaccharides, we showed that chain length and high sulfation density are the most important determinants for glycosaminoglycan-factor H interaction and clearly differ from properdin-heparinoid interaction. Coincubation of properdin and factor H did not hamper HS/heparin binding of one another, indicating recognition of different nonoverlapping epitopes on HS/heparin by factor H and properdin. Finally we showed that certain low anticoagulant heparinoids can inhibit properdin binding to tubular HS, with a minor effect on factor H binding to tubular HS. As a result, these heparinoids can control the alternative complement pathway. In conclusion, factor H and properdin interact with different HS epitopes of PTECs. These interactions can be manipulated with some low anticoagulant heparinoids, which can be important for preventing complement-derived tubular injury in proteinuric renal diseases.

Neuropilin-1 and neuropilin-2 are differentially expressed in human proteinuric nephropathies and cytokine-stimulated proximal tubular cells.

PubMed

Schramek, Herbert; Sarközi, Rita; Lauterberg, Christina; Kronbichler, Andreas; Pirklbauer, Markus; Albrecht, Rudolf; Noppert, Susie-Jane; Perco, Paul; Rudnicki, Michael; Strutz, Frank M; Mayer, Gert

2009-11-01

Neuropilin-1 (NRP1) and neuropilin-2 (NRP2) are transmembrane glycoproteins with large extracellular domains that interact with class 3 semaphorins, vascular endothelial growth factor (VEGF) family members, and ligands, such as hepatocyte growth factor, platelet-derived growth factor BB, transforming growth factor-beta1 (TGF-beta1), and fibroblast growth factor2 (FGF2). Neuropilins (NRPs) have been implicated in tumor growth and vascularization, as novel mediators of the primary immune response and in regeneration and repair; however, their role in renal pathophysiology is largely unknown. Here, we report upregulation of tubular and interstitial NRP2 protein expression in patients with focal segmental glomerulosclerosis (FSGS). In an additional cohort of patients with minimal change disease (MCD), membranous nephropathy (MN), and FSGS, elevated NRP2 mRNA expression in kidney biopsies inversely correlated with estimated glomerular filtration rate (eGFR) at the time of biopsy. Furthermore, upregulation of NRP2 mRNA correlated with post-bioptic decline of kidney function. Expression of NRP1 and NRP2 in human proximal tubular cells (PTCs) was differentially affected after stimulation with TGF-beta1, interleukin-1beta (IL-1beta), and oncostatin M (OSM). Although the pro-fibrotic mediators, TGF-beta1 and IL-1beta, induced upregulation of NRP2 expression but downregulation of NRP1 expression, OSM stimulated the expression of both NRP1 and NRP2. Basal and OSM-induced NRP1 mRNA expression, as well as TGF-beta1-induced NRP2 mRNA and protein expression were partially mediated by MEK1/2-ERK1/2 signaling. This is the first report suggesting a differential role of NRP1 and NRP2 in renal fibrogenesis, and TGF-beta1, IL-1beta, and OSM represent the first ligands known to stimulate NRP2 expression in mammalian cells.

Fanconi syndrome and severe polyuria: an uncommon clinicobiological presentation of a Gitelman syndrome

PubMed Central

2014-01-01

Background Gitelman syndrome is an autosomal recessive tubulopathy characterized by hypokalemia, hypomagnesemia, metabolic alkalosis and hypocalciuria. The majority of patients do not present with symptoms until late childhood or adulthood, and the symptoms are generally mild. We report here the first case of Gitelman syndrome presenting with the biological features of Fanconi syndrome and an early polyuria since the neonatal period. We discuss in this article the atypical electrolytes losses found in our patient, as well as the possible mechanisms of severe polyuria. Case presentation A 6-year-old Caucasian girl was admitted via the Emergency department for vomiting, and initial laboratory investigations found hyponatremia, hypokalemia, metabolic acidosis with normal anion gap, hypophosphatemia, and hypouricemia. Urinalysis revealed Na, K, Ph and uric acid losses. Thus, the initial biological profile was in favor of a proximal tubular defect. However, etiological investigations were inconclusive and the patient was discharged with potassium chloride and phosphorus supplementation. Three weeks later, further laboratory analysis indicated persistent hypokalemia, a metabolic alkalosis, hypomagnesemia, and hypocalciuria. We therefore sequenced the SLC12A3 gene and found a compound heterozygosity for 2 known missense mutations. Conclusions Gitelman syndrome can have varying and sometimes atypical presentations, and should be suspected in case of hypokalemic tubular disorders that do not belong to any obvious syndromic entity. In this case, the proximal tubular dysfunction could be secondary to the severe hypokalemia. This report emphasizes the need for clinicians to repeat laboratory tests in undiagnosed tubular disorders, especially not during decompensation episodes. PMID:25112827

Models for coupling of salt and water transport; Proximal tubular reabsorption in Necturus kidney.

PubMed

Sackin, H; Boulpaep, E L

1975-12-01

Models for coupling of salt and water transport are developed with two important assumptions appropriate for leaky epithelia. (a) The tight junction is permeable to both sale and water. (b) Active Na transport into the lateral speces is assumed to occur uniformly along the length of the channel. The proposed models deal specifically with the intraepithelial mechanism of proximal tubular resbsorption in the Necturus kidney although they have implications for epithelial transport in the gallbladder and small intestine as well. The first model (continuous version) is similar to the standing gradient model devised by Diamond and Bossert but used different boundary conditions. In contrast to Diamond and Bossert's model, the predicted concentration profiles are relatively flat with no sizable gradients along the interspace. The second model (compartment version) expands Curran's model of epithelial salt and water transport by including additional compartments and considering both electrical and chemical driving forces for individual Na and Cl ions as well as hydraulic and osmotic driving forces for water. In both models, ion and water fluxes are investigated as a function of the transport parameters. The behavior of the models is consistent with previously suggested mechanisms for the control of net transport, particularly during saline diuresis. Under all conditions the predicted ratio of net solute to solvent flux, or emergent concentration, deviates from exact isotonicity (except when the basement membrane has an appreciable salt reflection coefficient). However, the degree of hypertonicity may be small enough to be experimentally indistinguishable from isotonic transport.

Porcine proximal tubular cells (LLC-PK1) are able to tolerate high levels of lithium chloride in vitro: assessment of the influence of 1-20 mM LiCl on cell death and alterations in cell biology and biochemistry.

PubMed

Lucas, Kirsten C; Hart, David A; Becker, Rolf W

2010-01-25

Lithium, a prophylactic drug for the treatment of bipolar disorder, is prescribed with caution due to its side effects, including renal damage. In this study porcine LLC-PK1 renal tubular cells were used to establish the direct toxicity of lithium on proximal cells and gain insights into the molecular mechanisms involved. In the presence of LiCl, cell proliferation exhibited insignificant decreases in a concentration-dependent manner, but once confluent, constant cell numbers were observed. Cell cycle studies indicated a small dose-dependent accumulation of cells in the G2/M stage after 24 h, as well as an increase in cells in the G0/G1 phase after treatment with 1-10 mM LiCl, but not at 20 mM LiCl. No evidence of apoptosis was observed based on cell morphology or DNA fragmentation studies, or evidence of protein expression changes for Bax, Bcl-2, and p53 proteins using immunocytochemistry. In addition caspases 3, 8 and 9 activity remained unaltered between control and lithium-treated cultures. To conclude, exposure to high concentrations of lithium did not result in overt toxic effects to LLC-PK1 renal cells, although LiCl did alter some aspects of cell behaviour, which could potentially influence function over time.

Tight junctions of the proximal tubule and their channel proteins.

PubMed

Fromm, Michael; Piontek, Jörg; Rosenthal, Rita; Günzel, Dorothee; Krug, Susanne M

2017-08-01

The renal proximal tubule achieves the majority of renal water and solute reabsorption with the help of paracellular channels which lead through the tight junction. The proteins forming such channels in the proximal tubule are claudin-2, claudin-10a, and possibly claudin-17. Claudin-2 forms paracellular channels selective for small cations like Na + and K + . Independently of each other, claudin-10a and claudin-17 form anion-selective channels. The claudins form the paracellular "pore pathway" and are integrated, together with purely sealing claudins and other tight junction proteins, in the belt of tight junction strands surrounding the tubular epithelial cells. In most species, the proximal tubular tight junction consists of only 1-2 (pars convoluta) to 3-5 (pars recta) horizontal strands. Even so, they seal the tubule very effectively against leak passage of nutrients and larger molecules. Remarkably, claudin-2 channels are also permeable to water so that 20-25% of proximal water absorption may occur paracellularly. Although the exact structure of the claudin-2 channel is still unknown, it is clear that Na + and water share the same pore. Already solved claudin crystal structures reveal a characteristic β-sheet, comprising β-strands from both extracellular loops, which is anchored to a left-handed four-transmembrane helix bundle. This allowed homology modeling of channel-forming claudins present in the proximal tubule. The surface of cation- and anion-selective claudins differ in electrostatic potentials in the area of the proposed ion channel, resulting in the opposite charge selectivity of these claudins. Presently, while models of the molecular structure of the claudin-based oligomeric channels have been proposed, its full understanding has only started.

A novel Ile1455Thr variant in the skeletal muscle sodium channel alpha-subunit in a patient with a severe adult-onset proximal myopathy with electrical myotonia and a patient with mild paramyotonia phenotype.

PubMed

Bednarz, Marcin; Stunnenberg, Bas C; Kusters, Benno; Kamsteeg, Erik-Jan; Saris, Christiaan G; Groome, James; Winston, Vern; Meola, Giovanni; Jurkat-Rott, Karin; Voermans, Nicol C

2017-02-01

In sodium channelopathies, a severe fixed myopathy caused by a dominant mutation is rare. We describe two unrelated patients with a novel variant, p.Ile1455Thr, with phenotypes of paramyotonia in one case and fixed proximal myopathy with latent myotonia in another. In-vitro whole cell patch-clamp studies show that the mutation slows inactivation and accelerates recovery, in line with other paramyotonia variants with destabilized fast inactivation as pathomechanism. Additionally, p.IleI1455 causes a loss-of-function by reduced membrane insertion, right-shift of activation, and slowed kinetics. Molecular dynamics simulations comparing wild type and mutant Nav1.4 showed that threonine substitution hindered D4S4 mobility in response to membrane depolarization, consistent with effects of the mutation on channel inactivation. The fixed myopathy is likely to be associated to gain-of-function leading to sodium accumulation, regional edema, T-tubular swelling and mitochondrial stress. A possible contribution of the loss-of-function features towards myotonia and myopathy is discussed. Copyright © 2016. Published by Elsevier B.V.

Secretory NaCl and volume flow in renal tubules.

PubMed

Beyenbach, K W

1986-05-01

This review attempts to give a retrospective survey of the available evidence concerning the secretion of NaCl and fluid in renal tubules of the vertebrate kidney. In the absence of glomerular filtration, epithelial secretory mechanisms, which to this date have not been elucidated, are responsible for the renal excretion of NaCl and water in aglomerular fish. However, proximal tubules isolated from glomerular fish kidneys of the flounder, killifish, and the shark also have the capacity to secrete NaCl and fluid. In shark proximal tubules, fluid secretion appears to be driven via secondary active transport of Cl. In another marine vertebrate, the sea snake, secretion of Na (presumably NaCl) and fluid is observed in freshwater-adapted and water-loaded animals. Proximal tubules of mammals can be made to secrete NaCl in vitro together with secretion of aryl acids. An epithelial cell line derived from dog kidney exhibits secondary active secretion of Cl when stimulated with catecholamines. Tubular secretion of NaCl and fluid may serve a variety of renal functions, all of which are considered here. The occurrence of NaCl and fluid secretion in glomerular proximal tubules of teleosts, elasmobranchs, and reptiles and in mammalian renal tissue cultures suggests that the genetic potential for NaCl secretion is present in every vertebrate kidney.

Increased Fatty Acid Oxidation in Differentiated Proximal Tubular Cells Surviving a Reversible Episode of Acute Kidney Injury.

PubMed

Bataille, Aurélien; Galichon, Pierre; Chelghoum, Nadjim; Oumoussa, Badreddine Mohand; Ziliotis, Marie-Julia; Sadia, Iman; Vandermeersch, Sophie; Simon-Tillaux, Noémie; Legouis, David; Cohen, Raphaël; Xu-Dubois, Yi-Chun; Commereuc, Morgane; Rondeau, Eric; Le Crom, Stéphane; Hertig, Alexandre

2018-06-19

Fatty acid oxidation (FAO), the main source of energy produced by tubular epithelial cells in the kidney, was found to be defective in tubulo-interstitial samples dissected out in kidney biopsies from patients with chronic kidney disease (CKD). Experimental data indicated that this decrease was a strong determinant of renal fibrogenesis, hence a focus for therapeutic interventions. Nevertheless, whether persistently differentiated renal tubules, surviving in a pro-fibrotic environment, also suffer from a decrease in FAO, is currently unknown. To address this question, we isolated proximal tubules captured ex vivo on the basis of the expression of an intact brush border antigen (Prominin-1) in C57BL6/J mice subjected to a controlled, two-hit model of renal fibrosis (reversible ischemic acute kidney injury (AKI) or sham surgery, followed by angiotensin 2 administration). A transcriptomic high throughput sequencing was performed on total mRNA from these cells, and on whole kidneys. In contrast to mice subjected to sham surgery, mice with a history of AKI displayed histologically more renal fibrosis when exposed to angiotensin 2. High throughput RNA sequencing, principal component analysis and clustering showed marked consistency within experimental groups. As expected, FAO transcripts were decreased in whole fibrotic kidneys. Surprisingly, however, up- rather than down-regulation of metabolic pathways (oxidative phosphorylation, fatty acid metabolism, glycolysis, and PPAR signalling pathway) was a hallmark of the differentiated tubules captured from fibrotic kidneys. Immunofluorescence co-staining analysis confirmed that the expression of FAO enzymes was dependent of tubular trophicity. These data suggest that in differentiated proximal tubules energetic hyperactivity is promoted concurrently with organ fibrogenesis. © 2018 The Author(s). Published by S. Karger AG, Basel.

Nonalbumin proteinuria predominates in biopsy-proven tenofovir nephrotoxicity.

PubMed

Sise, Meghan E; Hirsch, Jamie S; Canetta, Pietro A; Herlitz, Leal; Mohan, Sumit

2015-05-15

Tenofovir disoproxil fumarate (TDF) nephrotoxicity is characterized by proximal renal tubular injury and dysmorphic mitochondria resulting in proteinuria, orthoglycemic glycosuria, and other markers of proximal tubular dysfunction. The objective of this study was to determine the pattern of proteinuria in patients with biopsy-proven TDF nephrotoxicity. Retrospective chart review. Patients with biopsy-proven TDF nephrotoxicity were identified and their medical charts and biopsy reports were reviewed. Comparison was made with HIV-infected patients not on TDF who underwent kidney biopsy. We identified 43 biopsy-proven cases of TDF nephrotoxicity; mean age 54.7 ± 0.4 years, 53% men, 42% whites. Thirty-seven cases reported proteinuria by dipstick of which only 60% had at least 2+ proteinuria. Twenty-seven patients had urine protein quantified by either 24-h collection or spot urine protein-to-creatinine ratio; median proteinuria was 1742 mg/day [interquartile range (IQR) 1200-2000 mg] and 1667 mg/g creatinine (IQR 851-1967 mg/g), respectively. Ten patients had concurrent urinary albumin measured, with a median 236 mg/g creatinine (IQR 137-343 mg/g). The mean urine albumin-to-urine protein ratio (uAPR) was 0.17 (IQR 0.14-0.19), confirming that TDF nephrotoxicity is primarily associated with nonalbumin proteinuria. Control cases had a uAPR of 0.65 (IQR 0.55-0.79) P < 0.001. Histopathology showed the predominance of proximal tubular injury with characteristic mitochondrial abnormalities. In the largest published cohort of patients with biopsy-proven TDF nephrotoxicity, we show that low uAPR is a reliable feature of this disease. Because of the predominance of nonalbumin proteinuria, dipstick urinalysis may be unreliable in TDF nephrotoxicity.

Paralysis Episodes in Carbonic Anhydrase II Deficiency.

PubMed

Al-Ibrahim, Alia; Al-Harbi, Mosa; Al-Musallam, Sulaiman

2003-01-01

Carbonic anhydrase II (CAII) deficiency is an autosomal recessive disorder manifest by osteopetrosis, renal tubular acidosis, and cerebral calcification. Other features include growth failure and mental retardation. Complications of the osteopetrosis include frequent bone fractures, cranial nerve compression, and dental mal-occlusion. A hyper-chloremic metabolic acidosis, sometimes with hypokalemia, occurs due to renal tubular acidosis that may be proximal, distal, or more commonly, the combined type. Such patients may present with global hypotonia, muscle weakness or paralysis. We report a case of CA II deficiency with recurrent attacks of acute paralysis which was misdiagnosed initially as Guillian-Barre syndrome.

Alteration of Fatty Acid Oxidation in Tubular Epithelial Cells: From Acute Kidney Injury to Renal Fibrogenesis

PubMed Central

Simon, Noémie; Hertig, Alexandre

2015-01-01

Renal proximal tubular cells are the most energy-demanding cells in the body. The ATP that they use is mostly produced in their mitochondrial and peroxisomal compartments, by the oxidation of fatty acids. When those cells are placed under a biological stress, such as a transient hypoxia, fatty acid oxidation (FAO) is shut down for a period of time that outlasts injury, and carbohydrate oxidation does not take over. Facing those metabolic constraints, surviving tubular epithelial cells exhibit a phenotypic switch that includes cytoskeletal rearrangement and production of extracellular matrix proteins, most probably contributing to acute kidney injury-induced renal fibrogenesis, thence to the development of chronic kidney disease. Here, we review experimental evidence that dysregulation of FAO profoundly affects the fate of tubular epithelial cells, by promoting epithelial-to-mesenchymal transition, inflammation, and eventually interstitial fibrosis. Restoring physiological production of energy is undoubtedly a possible therapeutic approach to unlock the mesenchymal reprograming of tubular epithelial cells in the kidney. In this respect, the benefit of the use of fibrates is uncertain, but new drugs that could specifically target this metabolic pathway, and, hopefully, attenuate renal fibrosis merit future research. PMID:26301223

Autophagy activation promotes removal of damaged mitochondria and protects against renal tubular injury induced by albumin overload.

PubMed

Tan, Jin; Wang, Miaohong; Song, Shuling; Miao, Yuyang; Zhang, Qiang

2018-01-10

Proteinuria (albuminuria) is an important cause of aggravating tubulointerstitial injury. Previous studies have shown that autophagy activation can alleviate renal tubular epithelial cell injury caused by urinary protein, but the mechanism is not clear. Here, we investigated the role of clearance of damaged mitochondria in this protective effect. We found that albumin overload induces a significant increase in turnover of LC3-II and decrease in p62 protein level in renal proximal tubular (HK-2) cells in vitro. Albumin overload also induces an increase in mitochondrial damage. ALC, a mitochondrial torpent, alleviates mitochondrial damage induced by albumin overload and also decreases autophagy, while mitochondrial damage revulsant CCCP further increases autophagy. Furthermore, pretreatment of HK-2 cells with rapamycin reduced the amount of damaged mitochondria and the level of apoptosis induced by albumin overload. In contrast, blocking autophagy with chloroquine exerted an opposite effect. Taken together, our results indicated autophagy activation promotes removal of damaged mitochondria and protects against renal tubular injury caused by albumin overload. This further confirms previous research that autophagy activation is an adaptive response in renal tubular epithelial cells after urinary protein overload.

Mitochondria-targeted therapies for acute kidney injury.

PubMed

Tábara, Luis Carlos; Poveda, Jonay; Martin-Cleary, Catalina; Selgas, Rafael; Ortiz, Alberto; Sanchez-Niño, Maria D

2014-08-08

Acute kidney injury (AKI) is a serious clinical condition with no effective treatment. Tubular cells are key targets in AKI. Tubular cells and, specifically, proximal tubular cells are extremely rich in mitochondria and mitochondrial changes had long been known to be a feature of AKI. However, only recent advances in understanding the molecules involved in mitochondria biogenesis and dynamics and the availability of mitochondria-targeted drugs has allowed the exploration of the specific role of mitochondria in AKI. We now review the morphological and functional mitochondrial changes during AKI, as well as changes in the expression of mitochondrial genes and proteins. Finally, we summarise the current status of novel therapeutic strategies specifically targeting mitochondria such as mitochondrial permeability transition pore (MPTP) opening inhibitors (cyclosporine A (CsA)), quinone analogues (MitoQ, SkQ1 and SkQR1), superoxide dismutase (SOD) mimetics (Mito-CP), Szeto-Schiller (SS) peptides (Bendavia) and mitochondrial division inhibitors (mdivi-1). MitoQ, SkQ1, SkQR1, Mito-CP, Bendavia and mdivi-1 have improved the course of diverse experimental models of AKI. Evidence for a beneficial effect of CsA on human cardiac ischaemia-reperfusion injury derives from a clinical trial; however, CsA is nephrotoxic. MitoQ and Bendavia have been shown to be safe for humans. Ongoing clinical trials are testing the efficacy of Bendavia in AKI prevention following renal artery percutaneous transluminal angioplasty.

Intestinal atresia and ectopia in a bovine fetus.

PubMed

Lejeune, B; Miclard, J; Stoffel, M H; Meylan, M

2011-07-01

A 2-year-old Red Holstein cow was presented with uterine torsion at 235 days of pregnancy. The fetus extracted by cesarean section had weak vital signs and marked abdominal distention. An edematous pouch that contained tubular structures with peristaltic activity was associated with the umbilical cord. Because of poor prognosis, both dam and fetus were euthanized. At necropsy, the fetus had severe distention of the forestomachs, abomasum, and proximal small intestine; absence of distal small intestine, cecum, and proximal colon; atresia of the 2 blind ends of the intestine; and atrophy of distal colon and rectum. The tubular structures associated with the umbilical cord were identified as the segments of intestine that were absent in the fetus. Intestinal atresia combined with ectopia may be caused by local ischemia during temporary herniation and rotation of the fetal gut into the extraembryonic coelom. The close connection between ectopic intestine and amniotic sheath of the umbilical cord in this case may have facilitated vascularization and allowed development and viability of the ectopic intestine. © The Authors 2011

Combination Direct Renin Inhibition with Angiotensin Type 1 Receptor Blockade improves Aldosterone but does not improve Kidney Injury in the Transgenic Ren2 rat

PubMed Central

Whaley-Connell, Adam; Habibi, Javad; Nistala, Ravi; Hayden, Melvin R; Pulakat, Lakshmi; Sinak, Catherine; Locher, Bonnie; Ferrario, Carlos M; Sowers, James R

2012-01-01

Enhanced renin-angiotensin-aldosterone system (RAAS) activation contributes to proteinuria and chronic kidney disease by increasing glomerular and tubulointerstitial oxidative stress, promotion of fibrosis. Renin activation is the rate limiting step in angiotensin (Ang II) and aldosterone generation, and recent work suggests direct renin inhibition improves proteinuria comparable to that seen with Ang type 1 receptor (AT1R) blockade. This is important as, even with contemporary use of AT1R blockade, the burden of kidney disease remains high. Thereby, we sought to determine if combination direct renin inhibition with AT1R blockade in vivo, via greater attenuation of kidney oxidative stress, would attenuate glomerular and proximal tubule injury to a greater extent than either intervention alone. We utilized the transgenic Ren2 rat with increased tissue RAS activity and higher serum levels of aldosterone, which manifests hypertension and proteinuria. Ren2 rats were treated with renin inhibition (aliskiren), AT1R blockade (valsartan), the combination (aliskiren+valsartan), or vehicle for 21 days. Compared to Sprague-Dawley controls, Ren2 rats displayed increased systolic pressure (SBP), circulating aldosterone, proteinuria and greater urine levels of the proximal tubule protein excretory marker beta-N-acetylglucosaminidase (β-NAG). These functional and biochemical alterations were accompanied by increases in kidney tissue NADPH oxidase subunit Rac1 and 3-nitrotyrosine (3-NT) content as well as fibronectin and collagen type III. These findings occurred in conjunction with reductions in the podocyte-specific protein podocin as well as the proximal tubule-specific megalin. Further, in transgenic animals there was increased tubulointerstitial fibrosis on light microscopy as well as ultrastructural findings of glomerular podocyte foot-process effacement and reduced tubular apical endosomal/lysosomal activity. Combination therapy led to greater reductions in SBP and serum aldosterone, but did not result in greater improvement in markers of glomerular and tubular injury (ie. β-NAG) compared to either intervention alone. Further, combination therapy did not improve markers of oxidative stress and podocyte and proximal tubule integrity in this transgenic model of RAAS-mediated kidney damage despite greater reductions in serum aldosterone and BP levels. PMID:22465166

Potential Use of Autologous Renal Cells from Diseased Kidneys for the Treatment of Renal Failure.

PubMed

George, Sunil K; Abolbashari, Mehran; Jackson, John D; Aboushwareb, Tamer; Atala, Anthony; Yoo, James J

2016-01-01

Chronic kidney disease (CKD) occurs when certain conditions cause the kidneys to gradually lose function. For patients with CKD, renal transplantation is the only treatment option that restores kidney function. In this study, we evaluated primary renal cells obtained from diseased kidneys to determine whether their normal phenotypic and functional characteristics are retained, and could be used for cell therapy. Primary renal cells isolated from both normal kidneys (NK) and diseased kidneys (CKD) showed similar phenotypic characteristics and growth kinetics. The expression levels of renal tubular cell markers, Aquaporin-1 and E-Cadherin, and podocyte-specific markers, WT-1 and Nephrin, were similar in both NK and CKD kidney derived cells. Using fluorescence- activated cell sorting (FACS), specific renal cell populations were identified and included proximal tubular cells (83.1% from NK and 80.3% from CKD kidneys); distal tubular cells (11.03% from NK and 10.9% from CKD kidneys); and podocytes (1.91% from NK and 1.78% from CKD kidneys). Ultra-structural analysis using scanning electron microscopy (SEM) revealed microvilli on the apical surface of cultured cells from NK and CKD samples. Moreover, transmission electron microscopy (TEM) analysis showed a similar organization of tight junctions, desmosomes, and other intracellular structures. The Na+ uptake characteristics of NK and CKD derived renal cells were also similar (24.4 mmol/L and 25 mmol/L, respectively) and no significant differences were observed in the protein uptake and transport characteristics of these two cell isolates. These results show that primary renal cells derived from diseased kidneys such as CKD have similar structural and functional characteristics to their counterparts from a normal healthy kidney (NK) when grown in vitro. This study suggests that cells derived from diseased kidney may be used as an autologous cell source for renal cell therapy, particularly in patients with CKD or end-stage renal disease (ESRD).

Reference values of renal tubular function tests are dependent on age and kidney function.

PubMed

Bech, Anneke P; Wetzels, Jack F M; Nijenhuis, Tom

2017-12-01

Electrolyte disorders due to tubular disorders are rare, and knowledge about validated clinical diagnostic tools such as tubular function tests is sparse. Reference values for tubular function tests are based on studies with small sample size in young healthy volunteers. Patients with tubular disorders, however, frequently are older and can have a compromised renal function. We therefore evaluated four tubular function tests in individuals with different ages and renal function. We performed furosemide, thiazide, furosemide-fludrocortisone, and desmopressin tests in healthy individuals aged 18-50 years, healthy individuals aged more than 50 years and individuals with compromised renal function. For each tubular function test we included 10 individuals per group. The responses in young healthy individuals were in line with previously reported values in literature. The maximal increase in fractional chloride excretion after furosemide was below the lower limit of young healthy individuals in 5/10 older subjects and in 2/10 patients with compromised renal function. The maximal increase in fractional chloride excretion after thiazide was below the lower limit of young healthy individuals in 6/10 older subjects and in 7/10 patients with compromised renal function. Median maximal urine osmolality after desmopressin was 1002 mosmol/kg H 2 O in young healthy individuals, 820 mosmol/kg H 2 O in older subjects and 624 mosmol/kg H 2 O in patients with compromised renal function. Reference values for tubular function tests obtained in young healthy adults thus cannot simply be extrapolated to older patients or patients with compromised kidney function. Larger validation studies are needed to define true reference values in these patient categories. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Expression patterns of the aquaporin gene family during renal development: influence of genetic variability.

PubMed

Parreira, Kleber S; Debaix, Huguette; Cnops, Yvette; Geffers, Lars; Devuyst, Olivier

2009-08-01

High-throughput analyses have shown that aquaporins (AQPs) belong to a cluster of genes that are differentially expressed during kidney organogenesis. However, the spatiotemporal expression patterns of the AQP gene family during tubular maturation and the potential influence of genetic variation on these patterns and on water handling remain unknown. We investigated the expression patterns of all AQP isoforms in fetal (E13.5 to E18.5), postnatal (P1 to P28), and adult (9 weeks) kidneys of inbred (C57BL/6J) and outbred (CD-1) mice. Using quantitative polymerase chain reaction (PCR), we evidenced two mRNA patterns during tubular maturation in C57 mice. The AQPs 1-7-11 showed an early (from E14.5) and progressive increase to adult levels, similar to the mRNA pattern observed for proximal tubule markers (Megalin, NaPi-IIa, OAT1) and reflecting the continuous increase in renal cortical structures during development. By contrast, AQPs 2-3-4 showed a later (E15.5) and more abrupt increase, with transient postnatal overexpression. Most AQP genes were expressed earlier and/or stronger in maturing CD-1 kidneys. Furthermore, adult CD-1 kidneys expressed more AQP2 in the collecting ducts, which was reflected by a significant delay in excreting a water load. The expression patterns of proximal vs. distal AQPs and the earlier expression in the CD-1 strain were confirmed by immunoblotting and immunostaining. These data (1) substantiate the clustering of important genes during tubular maturation and (2) demonstrate that genetic variability influences the regulation of the AQP gene family during tubular maturation and water handling by the mature kidney.

The Physiology Teacher, Vol. 5 No. 1.

ERIC Educational Resources Information Center

Reynolds, Orr E., Ed.

Outlined in this publication is a basic laboratory exercise which characterizes tubular secretion, using an isolated renal tubule preparation from teleost fish. Background information is given showing how these tubules of teleost fish, particularly marine teleosts, correspond to the proximal tubule of mammalian kidney. Materials needed, including…

Improved outcomes after technical modifications in tubularized incised plate urethroplasty for mid-shaft and proximal hypospadias.

PubMed

Tam, Yuk Him; Pang, Kristine Kit Yi; Wong, Yuen Shan; Tsui, Siu Yan; Wong, Hei Yi; Mou, Jennifer Wai Cheung; Chan, Kin Wai; Lee, Kim Hung

2016-11-01

To investigate and compare the outcomes after tubularized incised plate (TIP) urethroplasty in mid-shaft and proximal hypospadias using a standard and a modified technique. We conducted a retrospective study in 104 consecutive children who underwent mid-shaft or proximal TIP repairs from Jan 2007 to Sept 2015. Patients in Cohort One had dorsal dartos (DD) neourethral coverage while patients in Cohort Two had either de-epithelialized split preputial (DESP) or tunica vaginalis (TV) flap coverage. TV flap was used only when DESP flap was not sufficient to cover the neourethra. There were 52 patients each in Cohort One (DD, n = 52) and Cohort Two (DESP, n = 38; TV, n = 14) with no difference in ratio of mid-shaft/proximal between the two cohorts. At a median follow-up of 28 months, 36 patients (34.6 %) developed 47 complications including fistula (n = 19; 18.3 %) and neourethral dehiscence (n = 4; 3.8 %). Cohort One patients had significantly more fistula (28.8 vs 7.7 %; p = 0.005) and neourethral dehiscence (7.7 vs 0 %; p = 0.04) than Cohort Two. There was no difference between the two cohorts in the complication rates of meatal stenosis, recurrent ventral curvature and neourethral stricture. Both DESP and TV flap appear to be superior to DD in preventing fistula and neourethral dehiscence in non-distal TIP repairs.

Deferasirox-induced iron depletion promotes BclxL downregulation and death of proximal tubular cells

PubMed Central

Martin-Sanchez, Diego; Gallegos-Villalobos, Angel; Fontecha-Barriuso, Miguel; Carrasco, Susana; Sanchez-Niño, Maria Dolores; Lopez-Hernandez, Francisco J; Ruiz-Ortega, Marta; Egido, Jesus; Ortiz, Alberto; Sanz, Ana Belén

2017-01-01

Iron deficiency has been associated with kidney injury. Deferasirox is an oral iron chelator used to treat blood transfusion-related iron overload. Nephrotoxicity is the most serious and common adverse effect of deferasirox and may present as an acute or chronic kidney disease. However, scarce data are available on the molecular mechanisms of nephrotoxicity. We explored the therapeutic modulation of deferasirox-induced proximal tubular cell death in culture. Deferasirox induced dose-dependent tubular cell death and AnexxinV/7AAD staining showed features of apoptosis and necrosis. However, despite inhibiting caspase-3 activation, the pan-caspase inhibitor zVAD-fmk failed to prevent deferasirox-induced cell death. Moreover, zVAD increased deferasirox-induced cell death, a feature sometimes found in necroptosis. Electron microscopy identified mitochondrial injury and features of necrosis. However, neither necrostatin-1 nor RIP3 knockdown prevented deferasirox-induced cell death. Deferasirox caused BclxL depletion and BclxL overexpression was protective. Preventing iron depletion protected from BclxL downregulation and deferasirox cytotoxicity. In conclusion, deferasirox promoted iron depletion-dependent cell death characterized by BclxL downregulation. BclxL overexpression was protective, suggesting a role for BclxL downregulation in iron depletion-induced cell death. This information may be used to develop novel nephroprotective strategies. Furthermore, it supports the concept that monitoring kidney tissue iron depletion may decrease the risk of deferasirox nephrotoxicity. PMID:28139717

Deferasirox-induced iron depletion promotes BclxL downregulation and death of proximal tubular cells.

PubMed

Martin-Sanchez, Diego; Gallegos-Villalobos, Angel; Fontecha-Barriuso, Miguel; Carrasco, Susana; Sanchez-Niño, Maria Dolores; Lopez-Hernandez, Francisco J; Ruiz-Ortega, Marta; Egido, Jesus; Ortiz, Alberto; Sanz, Ana Belén

2017-01-31

Iron deficiency has been associated with kidney injury. Deferasirox is an oral iron chelator used to treat blood transfusion-related iron overload. Nephrotoxicity is the most serious and common adverse effect of deferasirox and may present as an acute or chronic kidney disease. However, scarce data are available on the molecular mechanisms of nephrotoxicity. We explored the therapeutic modulation of deferasirox-induced proximal tubular cell death in culture. Deferasirox induced dose-dependent tubular cell death and AnexxinV/7AAD staining showed features of apoptosis and necrosis. However, despite inhibiting caspase-3 activation, the pan-caspase inhibitor zVAD-fmk failed to prevent deferasirox-induced cell death. Moreover, zVAD increased deferasirox-induced cell death, a feature sometimes found in necroptosis. Electron microscopy identified mitochondrial injury and features of necrosis. However, neither necrostatin-1 nor RIP3 knockdown prevented deferasirox-induced cell death. Deferasirox caused BclxL depletion and BclxL overexpression was protective. Preventing iron depletion protected from BclxL downregulation and deferasirox cytotoxicity. In conclusion, deferasirox promoted iron depletion-dependent cell death characterized by BclxL downregulation. BclxL overexpression was protective, suggesting a role for BclxL downregulation in iron depletion-induced cell death. This information may be used to develop novel nephroprotective strategies. Furthermore, it supports the concept that monitoring kidney tissue iron depletion may decrease the risk of deferasirox nephrotoxicity.

Effects of lead intoxication on intercellular junctions and biochemical alterations of the renal proximal tubule cells.

PubMed

Navarro-Moreno, L G; Quintanar-Escorza, M A; González, S; Mondragón, R; Cerbón-Solorzáno, J; Valdés, J; Calderón-Salinas, J V

2009-10-01

Lead intoxication is a worldwide health problem which frequently affects the kidney. In this work, we studied the effects of chronic lead intoxication (500 ppm of Pb in drinking water during seven months) on the structure, function and biochemical properties of rat proximal tubule cells. Lead-exposed animals showed increased lead concentration in kidney, reduction of calcium and amino acids uptake, oxidative damage and glucosuria, proteinuria, hematuria and reduced urinary pH. These biochemical and physiological alterations were related to striking morphological modifications in the structure of tubule epithelial cells and in the morphology of their mitochondria, nuclei, lysosomes, basal and apical membranes. Interestingly, in addition to the nuclei, inclusion bodies were found in the cytoplasm and in mitochondria. The epithelial cell structure modifications included an early loss of the apical microvillae, followed by a decrement of the luminal space and the respective apposition and proximity of apical membranes, resulting in the formation of atypical intercellular contacts and adhesion structures. Similar but less marked alterations were observed in subacute lead intoxication as well. Our work contributes in the understanding of the physiopathology of lead intoxication on the structure of renal tubular epithelial cell-cell contacts in vivo.

Xenon treatment protects against cold ischemia associated delayed graft function and prolongs graft survival in rats.

PubMed

Zhao, H; Watts, H R; Chong, M; Huang, H; Tralau-Stewart, C; Maxwell, P H; Maze, M; George, A J T; Ma, D

2013-08-01

Prolonged hypothermic storage causes ischemia-reperfusion injury (IRI) in the renal graft, which is considered to contribute to the occurrence of the delayed graft function (DGF) and chronic graft failure. Strategies are required to protect the graft and to prolong renal graft survival. We demonstrated that xenon exposure to human proximal tubular cells (HK-2) led to activation of range of protective proteins. Xenon treatment prior to or after hypothermia-hypoxia challenge stabilized the HK-2 cellular structure, diminished cytoplasmic translocation of high-mobility group box (HMGB) 1 and suppressed NF-κB activation. In the syngeneic Lewis-to-Lewis rat model of kidney transplantation, xenon exposure to donors before graft retrieval or to recipients after engraftment decreased caspase-3 expression, localized HMGB-1 within nuclei and prevented TLR-4/NF-κB activation in tubular cells; serum pro-inflammatory cytokines IL-1β, IL-6 and TNF-α were reduced and renal function was preserved. Xenon treatment of graft donors or of recipients prolonged renal graft survival following IRI in both Lewis-to-Lewis isografts and Fischer-to-Lewis allografts. Xenon induced cell survival or graft functional recovery was abolished by HIF-1α siRNA. Our data suggest that xenon treatment attenuates DGF and enhances graft survival. This approach could be translated into clinical practice leading to a considerable improvement in long-term graft survival. © Copyright 2013 The American Society of Transplantation and the American Society of Transplant Surgeons.

Carbonic anhydrase II binds to and increases the activity of the epithelial sodium-proton exchanger, NHE3

PubMed Central

Krishnan, Devishree; Liu, Lei; Wiebe, Shane A.; Casey, Joseph R.; Cordat, Emmanuelle; Alexander, R. Todd

2016-01-01

Two-thirds of sodium filtered by the renal glomerulus is reabsorbed from the proximal tubule via a sodium/proton exchanger isoform 3 (NHE3)-dependent mechanism. Since sodium and bicarbonate reabsorption are coupled, we postulated that the molecules involved in their reabsorption [NHE3 and carbonic anhydrase II (CAII)] might physically and functionally interact. Consistent with this, CAII and NHE3 were closely associated in a renal proximal tubular cell culture model as revealed by a proximity ligation assay. Direct physical interaction was confirmed in solid-phase binding assays with immobilized CAII and C-terminal NHE3 glutathione-S-transferase fusion constructs. To assess the effect of CAII on NHE3 function, we expressed NHE3 in a proximal tubule cell line and measured NHE3 activity as the rate of intracellular pH recovery, following an acid load. NHE3-expressing cells had a significantly greater rate of intracellular pH recovery than controls. Inhibition of endogenous CAII activity with acetazolamide significantly decreased NHE3 activity, indicating that CAII activates NHE3. To ascertain whether CAII binding per se activates NHE3, we expressed NHE3 with wild-type CAII, a catalytically inactive CAII mutant (CAII-V143Y), or a mutant unable to bind other transporters (CAII-HEX). NHE3 activity increased upon wild-type CAII coexpression, but not in the presence of the CAII V143Y or HEX mutant. Together these studies support an association between CAII and NHE3 that alters the transporter’s activity. PMID:26041446

Idiopathic Fanconi's syndrome with nephrogenic diabetes insipidus in a child who presented as vitamin D resistant rickets--a case report and review of literature.

PubMed

Patra, Soumya; Nadri, Gulnaz; Chowdhary, Harish; Pemde, Harish K; Singh, Varinder; Chandra, Jagdish

2011-01-01

Fanconi's syndrome is a complex of multiple tubular dysfunctions of proximal tubular cells occurring alone or in association with a variety of inherited (primary) or acquired (secondary) disorders. It is characterized by aminoaciduria, normoglycemic glycosuria, tubular proteinuria without hematuria, metabolic acidosis without anion gap and excessive urinary excretion of phosphorous, calcium, uric acid, bicarbonate, sodium, potassium and magnesium. Diabetes insipidus is a disease of collecting tubules and a child mainly presents with dehydration and hypernatremia. We report the first case of idiopathic Fanconi's syndrome along with nephrogenic diabetes insipidus (NDI) in a child who presented to us as resistant rickets. Medline search did not reveal any case of nephrogenic diabetes insipidus associated with idiopathic Fanconi's syndrome. We hypothesized that the NDI may be due to severe hypokalemia induced tubular dysfunction. The child was treated for hypophosphatemic rickets with severe metabolic acidosis and the treatment for NDI was also given. Now he has healed rickets and normal blood pH, sodium and osmolarity.

Lysosomal Changes in Renal Proximal Tubular Epithelial Cells of Male Sprague Dawley Rats Following Decalin Exposure

DTIC Science & Technology

1990-01-01

induced by decalin exposure are processes, accelerated apoptosis has been describedin renal tissue with hydronephrosis (6), during the clearly intact...experimental hydronephrosis in topathology and cell proliferation induced by 2,2.4- the rat. Lab. Invest. 56(3): 273-281. trimethylpentane in the

Role of serotonin in the regulation of renal proximal tubular epithelial cells.

PubMed

Erikci, Acelya; Ucar, Gulberk; Yabanoglu-Ciftci, Samiye

2016-08-01

In various renal injuries, tissue damage occurs and platelet activation is observed. Recent studies suggest that some factors, such as serotonin, are released into microenvironment upon platelet activation following renal injury. In the present study, we aimed to investigate whether platelets and platelet-released serotonin are involved in the functional regulation of renal proximal tubular epithelial cells (PTECs). PTECs were obtained by primary cell culture and treated with platelet lysate (PL) (2 × 10(6)/mL, 4 × 10(6)/mL, 8 × 10(6)/mL) or serotonin (1 μM or 5 μM) for 12 or 24 h. Phenotypic transdifferentiation of epithelial cells into myofibroblasts were demonstrated under light microscope and confirmed by the determination of α-smooth muscle actin gene expression. Serotonin and PL were shown to induce epithelial-mesenchymal transdifferentiation of PTECs. After stimulation of PTECs with serotonin or PL, matrix metalloproteinase-2, tissue inhibitor of metalloproteinase-1, and collagen-α1 gene expressions, which were reported to be elevated in renal injury, were determined by real-time PCR and found to be upregulated. Expressions of some inflammatory cytokines such as tumor necrosis factor-α, interleukin-6, and transforming growth factor-β1 were found to be increased in both protein and gene levels. Recently there is no published report on the effect of serotonin on renal PTECs. Results obtained in this study have lightened the role of serotonin and platelet-mediated effects of serotonin on fibrotic and inflammatory processes in PTECs.

Models for coupling of salt and water transport; Proximal tubular reabsorption in Necturus kidney

PubMed Central

Sackin, H; Boulpaep, EL

1975-01-01

Models for coupling of salt and water transport are developed with two important assumptions appropriate for leaky epithelia. (a) The tight junction is permeable to both sale and water. (b) Active Na transport into the lateral speces is assumed to occur uniformly along the length of the channel. The proposed models deal specifically with the intraepithelial mechanism of proximal tubular resbsorption in the Necturus kidney although they have implications for epithelial transport in the gallbladder and small intestine as well. The first model (continuous version) is similar to the standing gradient model devised by Diamond and Bossert but used different boundary conditions. In contrast to Diamond and Bossert's model, the predicted concentration profiles are relatively flat with no sizable gradients along the interspace. The second model (compartment version) expands Curran's model of epithelial salt and water transport by including additional compartments and considering both electrical and chemical driving forces for individual Na and Cl ions as well as hydraulic and osmotic driving forces for water. In both models, ion and water fluxes are investigated as a function of the transport parameters. The behavior of the models is consistent with previously suggested mechanisms for the control of net transport, particularly during saline diuresis. Under all conditions the predicted ratio of net solute to solvent flux, or emergent concentration, deviates from exact isotonicity (except when the basement membrane has an appreciable salt reflection coefficient). However, the degree of hypertonicity may be small enough to be experimentally indistinguishable from isotonic transport. PMID:1104761

Fluorescent Labeling and Biodistribution of Latex Nanoparticles Formed by Surfactant-Free RAFT Emulsion Polymerization.

PubMed

Poon, Cheuk Ka; Tang, Owen; Chen, Xin-Ming; Kim, Byung; Hartlieb, Matthias; Pollock, Carol A; Hawkett, Brian S; Perrier, Sébastien

2017-10-01

The authors report the preparation of a novel range of functional polyacrylamide stabilized polystyrene nanoparticles, obtained by surfactant-free reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization, their fluorescent tagging, cellular uptake, and biodistribution. The authors show the versatility of the RAFT emulsion process for the design of functional nanoparticles of well-defined size that can be used as drug delivery vectors. Functionalization with a fluorescent tag offers a useful visualization tool for tracing, localization, and clearance studies of these carriers in biological models. The studies are carried out by labeling the sterically stabilized latex particles chemically with rhodamine B. The fluorescent particles are incubated in a healthy human renal proximal tubular cell line model, and intravenously injected into a mouse model. Cellular localization and biodistribution of these particles on the biological models are explored. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Albumin-bound fatty acids but not albumin itself alter redox balance in tubular epithelial cells and induce a peroxide-mediated redox-sensitive apoptosis

PubMed Central

Ruggiero, Christine; Elks, Carrie M.; Kruger, Claudia; Cleland, Ellen; Addison, Kaity; Noland, Robert C.

2014-01-01

Albuminuria is associated with metabolic syndrome and diabetes. It correlates with the progression of chronic kidney disease, particularly with tubular atrophy. The fatty acid load on albumin significantly increases in obesity, presenting a proinflammatory environment to the proximal tubules. However, little is known about changes in the redox milieu during fatty acid overload and how redox-sensitive mechanisms mediate cell death. Here, we show that albumin with fatty acid impurities or conjugated with palmitate but not albumin itself compromised mitochondrial and cell viability, membrane potential and respiration. Fatty acid overload led to a redox imbalance which deactivated the antioxidant protein peroxiredoxin 2 and caused a peroxide-mediated apoptosis through the redox-sensitive pJNK/caspase-3 pathway. Transfection of tubular cells with peroxiredoxin 2 was protective and mitigated apoptosis. Mitochondrial fatty acid entry and ceramide synthesis modulators suggested that mitochondrial β oxidation but not ceramide synthesis may modulate lipotoxic effects on tubular cell survival. These results suggest that albumin overloaded with fatty acids but not albumin itself changes the redox environment in the tubules, inducing a peroxide-mediated redox-sensitive apoptosis. Thus, mitigating circulating fatty acid levels may be an important factor in both preserving redox balance and preventing tubular cell damage in proteinuric diseases. PMID:24500687

Transcription factor Nrf2 hyperactivation in early-phase renal ischemia-reperfusion injury prevents tubular damage progression.

PubMed

Nezu, Masahiro; Souma, Tomokazu; Yu, Lei; Suzuki, Takafumi; Saigusa, Daisuke; Ito, Sadayoshi; Suzuki, Norio; Yamamoto, Masayuki

2017-02-01

Acute kidney injury is a devastating disease with high morbidity in hospitalized patients and contributes to the pathogenesis of chronic kidney disease. An underlying mechanism of acute kidney injury involves ischemia-reperfusion injury which, in turn, induces oxidative stress and provokes organ damage. Nrf2 is a master transcription factor that regulates the cellular response to oxidative stress. Here, we examined the role of Nrf2 in the progression of ischemia-reperfusion injury-induced kidney damage in mice using genetic and pharmacological approaches. Both global and tubular-specific Nrf2 activation enhanced gene expression of antioxidant and NADPH synthesis enzymes, including glucose-6-phosphate dehydrogenase, and ameliorated both the initiation of injury in the outer medulla and the progression of tubular damage in the cortex. Myeloid-specific Nrf2 activation was ineffective. Short-term administration of the Nrf2 inducer CDDO during the initial phase of injury ameliorated the late phase of tubular damage. This inducer effectively protected the human proximal tubular cell line HK-2 from oxidative stress-mediated cell death while glucose-6-phosphate dehydrogenase knockdown increased intracellular reactive oxygen species. These findings demonstrate that tubular hyperactivation of Nrf2 in the initial phase of injury prevents the progression of reactive oxygen species-mediated tubular damage by inducing antioxidant enzymes and NADPH synthesis. Thus, Nrf2 may be a promising therapeutic target for preventing acute kidney injury to chronic kidney disease transition. Copyright © 2016 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

Claudins and renal salt transport.

PubMed

Muto, Shigeaki; Furuse, Mikio; Kusano, Eiji

2012-02-01

Tight junctions (TJs) are the most apical component of junctional complexes and regulate the movement of electrolytes and solutes by the paracellular pathway across epithelia. The defining ultrastructural features of TJs are strands of transmembrane protein particles that adhere to similar strands on adjacent cells. These strands are mainly composed of linearly polymerized integral membrane proteins called claudins. Claudins comprise a multigene family consisting of more than 20 members in mammals. Recent work has shown that claudins form barriers, determined by the paracellular electrical resistance and charge selectivity, and pores in the TJ strands. The paracellular pathways in renal tubular epithelia such as the proximal tubule, which reabsorbs the largest fraction of filtered NaCl and water, are important routes for the transport of electrolytes and water. Their transport characteristics vary among different nephron segments. Multiple claudins are expressed at TJs of individual nephron segments in a nephron segment-specific manner. Among them, claudin-2 is highly expressed at TJs of proximal tubules, which are leaky epithelia. Overexpression and knockdown of claudin-2 in epithelial cell lines, and knockout of the claudin-2 gene in mice, have demonstrated that claudin-2 forms high-conductance cation-selective pores in the proximal tubule. Here, we review the renal physiology of paracellular transport and the physiological roles of claudins in kidney function, especially claudin-2 and proximal tubule paracellular NaCl transport.

Transforming Growth Factor Beta 1 Drives a Switch in Connexin Mediated Cell-to-Cell Communication in Tubular Cells of the Diabetic Kidney.

PubMed

Hills, Claire; Price, Gareth William; Wall, Mark John; Kaufmann, Timothy John; Chi-Wai Tang, Sidney; Yiu, Wai Han; Squires, Paul Edward

2018-01-01

Changes in cell-to-cell communication have been linked to several secondary complications of diabetes, but the mechanism by which connexins affect disease progression in the kidney is poorly understood. This study examines a role for glucose-evoked changes in the beta1 isoform of transforming growth factor (TGFβ1), on connexin expression, gap-junction mediated intercellular communication (GJIC) and hemi-channel ATP release from tubular epithelial cells of the proximal renal nephron. Biopsy material from patients with and without diabetic nephropathy was stained for connexin-26 (CX26) and connexin-43 (CX43). Changes in expression were corroborated by immunoblot analysis in human primary proximal tubule epithelial cells (hPTECs) and model epithelial cells from human renal proximal tubules (HK2) cultured in either low glucose (5mmol/L) ± TGFβ1 (2-10ng/ml) or high glucose (25mmol/L) for 48h or 7days. Secretion of the cytokine was determined by ELISA. Paired whole cell patch clamp recordings were used to measure junctional conductance in control versus TGFβ1 treated (10ng/ml) HK2 cells, with carboxyfluorescein uptake and ATP-biosensing assessing hemi-channel function. A downstream role for ATP in mediating the effects of TGF-β1 on connexin mediated cell communication was assessed by incubating cells with ATPγS (1-100µM) or TGF-β1 +/- apyrase (5 Units/ml). Implications of ATP release were measured through immunoblot analysis of interleukin 6 (IL-6) and fibronectin expression. Biopsy material from patients with diabetic nephropathy exhibited increased tubular expression of CX26 and CX43 (P<0.01, n=10), data corroborated in HK2 and hPTEC cells cultured in TGFβ1 (10ng/ml) for 7days (P<0.001, n=3). High glucose significantly increased TGFβ1 secretion from tubular epithelial cells (P<0.001, n=3). The cytokine (10ng/ml) reduced junctional conductance between HK2 cells from 4.5±1.3nS in control to 1.15±0.9nS following 48h TGFβ1 and to 0.42±0.2nS after 7days TGFβ1 incubation (P<0.05, n=5). Acute (48h) and chronic (7day) challenge with TGFβ1 produced a carbenoxolone (200µM)-sensitive increase in carboxyfluorescein loading, matched by an increase in ATP release from 0.29±0.06μM in control to 1.99±0.47μM after 48hr incubation with TGFβ1 (10ng/ml; P<0.05, n=3). TGF-β1 (2-10ng/ml) and ATPγs (1-100µM) increased expression of IL-6 (P<0.001 n=3) and fibronectin (P<0.01 n=3). The effect of TGF-β1 on IL-6 and fibronectin expression was partially blunted when preincubated with apyrase (n=3). These data suggest that chronic exposure to glucose-evoked TGFβ1 induce an increase in CX26 and CX43 expression, consistent with changes observed in tubular epithelia from patients with diabetic nephropathy. Despite increased connexin expression, direct GJIC communication decreases, whilst hemichannel expression/function and paracrine release of ATP increases, changes that trigger increased levels of expression of interleukin 6 and fibronectin. Linked to inflammation and fibrosis, local increases in purinergic signals may exacerbate disease progression and highlight connexin mediated cell communication as a future therapeutic target for diabetic nephropathy. © 2018 The Author(s). Published by S. Karger AG, Basel.

Cellular Uptake and Localization of Polymyxins in Renal Tubular Cells Using Rationally Designed Fluorescent Probes

PubMed Central

Yun, Bo; Azad, Mohammad A. K.; Nowell, Cameron J.; Nation, Roger L.; Thompson, Philip E.; Roberts, Kade D.

2015-01-01

Polymyxins are cyclic lipopeptide antibiotics that serve as a last line of defense against Gram-negative bacterial superbugs. However, the extensive accumulation of polymyxins in renal tubular cells can lead to nephrotoxicity, which is the major dose-limiting factor in clinical use. In order to gain further insights into the mechanism of polymyxin-induced nephrotoxicity, we have rationally designed novel fluorescent polymyxin probes to examine the localization of polymyxins in rat renal tubular (NRK-52E) cells. Our design strategy focused on incorporating a dansyl fluorophore at the hydrophobic centers of the polymyxin core structure. To this end, four novel regioselectively labeled monodansylated polymyxin B probes (MIPS-9541, MIPS-9542, MIPS-9543, and MIPS-9544) were designed, synthesized, and screened for their antimicrobial activities and apoptotic effects against rat kidney proximal tubular cells. On the basis of the assessment of antimicrobial activities, cellular uptake, and apoptotic effects on renal tubular cells, incorporation of a dansyl fluorophore at either position 6 or 7 (MIPS-9543 and MIPS-9544, respectively) of the polymyxin core structure appears to be an appropriate strategy for generating representative fluorescent polymyxin probes to be utilized in intracellular imaging and mechanistic studies. Furthermore, confocal imaging experiments utilizing these probes showed evidence of partial colocalization of the polymyxins with both the endoplasmic reticulum and mitochondria in rat renal tubular cells. Our results highlight the value of these new fluorescent polymyxin probes and provide further insights into the mechanism of polymyxin-induced nephrotoxicity. PMID:26392495

Using optical coherence tomography (OCT) to evaluate the status of human donor kidneys (Conference Presentation)

NASA Astrophysics Data System (ADS)

Andrews, Peter M.; Konkel, Brandon; Anderson, Erik; Stein, Matthew; Cooper, Matthew; Verbesey, Jennifer E.; Ghasemian, Seyed; Chen, Yu

2016-02-01

The main cause of delayed renal function following the transplant of donor kidneys is ischemic induced acute tubular necrosis (ATN). The ability to determine the degree of ATN suffered by donor kidneys prior to their transplant would enable transplant surgeons to use kidneys that might otherwise be discarded and better predict post-transplant renal function. Currently, there are no reliable tests to determine the extent of ATN of donor kidneys prior to their transplant. In ongoing clinical trials, we have been using optical coherence tomography (OCT) to non-invasively image the superficial proximal tubules of human donor kidneys prior to and following transplant, and correlate these observations with post-transplant renal function. Thus far we have studied over 40 living donor kidneys and 10 cadaver donor kidneys, and demonstrated that this imaging can be performed in a sterile and expeditious fashion in the operating room (OR). Because of many variables associated with a diverse population of donors/recipients and transplant operation parameters, more transplant data must be collected prior to drawing definite conclusions. Nevertheless, our observations have thus far mirrored our previously published laboratory results indicating that damage to the kidney proximal tubules as indicated by tubule swelling is a good measure of post-transplant ATN and delayed graft function. We conclude that OCT is a useful procedure for analyzing human donor kidneys.

Fibroblast growth factor-23 increases mouse PGE2 production in vivo and in vitro.

PubMed

Syal, Ashu; Schiavi, Susan; Chakravarty, Sumana; Dwarakanath, Vangipuram; Quigley, Raymond; Baum, Michel

2006-02-01

Fibroblast growth factor-23 (FGF-23) has been implicated in the renal phosphate wasting in X-linked hypophosphatemia, tumor-induced osteomalacia, and autosomal dominant hypophosphatemic rickets. Recently, we demonstrated that Hyp mice have greater urinary PGE2 levels compared with C57/B6 mice and that indomethacin administration in vivo and in vitro ameliorates the phosphate transport defect in Hyp mice. To determine further whether altered prostaglandin metabolism plays a role in the renal phosphate transport defect in Hyp mice, we incubated renal proximal tubules with arachidonic acid. We find that PGE2 production was higher in Hyp mice than in C57/B6 mice. Incubation of C57/B6 mouse renal proximal tubules with FGF-23R176Q, an active mutant form of FGR23, increased tubular PGE2 production, an effect that was inhibited by 50 microM PD-98059 and 10 microM SB-203580, inhibitors of the MAP kinase pathway. C57/B6 mice injected with FGF-23R176Q had a approximately 10-fold increase in PGE2 excretion 24 h after intraperitoneal injection of FGF-23R176Q compared with vehicle-treated controls. Finally, we show that PGE2 inhibited both phosphate and volume absorption in mouse proximal convoluted tubules perfused in vitro and reduced brush-border membrane vesicle NaPi-2a protein abundance from renal cortex incubated in vitro with PGE2. In conclusion, FGF-23 increases urinary and renal tubular PGE2 production via the MAP kinase pathway and PGE2 inhibits proximal tubule phosphate transport.

Fibroblast growth factor-23 increases mouse PGE2 production in vivo and in vitro

PubMed Central

Syal, Ashu; Schiavi, Susan; Chakravarty, Sumana; Dwarakanath, Vangipuram; Quigley, Raymond; Baum, Michel

2014-01-01

Fibroblast growth factor-23 (FGF-23) has been implicated in the renal phosphate wasting in X-linked hypophosphatemia, tumor-induced osteomalacia, and autosomal dominant hypophosphatemic rickets. Recently, we demonstrated that Hyp mice have greater urinary PGE2 levels compared with C57/B6 mice and that indomethacin administration in vivo and in vitro ameliorates the phosphate transport defect in Hyp mice. To determine further whether altered prostaglandin metabolism plays a role in the renal phosphate transport defect in Hyp mice, we incubated renal proximal tubules with arachidonic acid. We find that PGE2 production was higher in Hyp mice than in C57/B6 mice. Incubation of C57/B6 mouse renal proximal tubules with FGF-23R176Q, an active mutant form of FGR23, increased tubular PGE2 production, an effect that was inhibited by 50 μM PD-98059 and 10 μM SB-203580, inhibitors of the MAP kinase pathway. C57/B6 mice injected with FGF-23R176Q had a ~10-fold increase in PGE2 excretion 24 h after intraperitoneal injection of FGF-23R176Q compared with vehicle-treated controls. Finally, we show that PGE2 inhibited both phosphate and volume absorption in mouse proximal convoluted tubules perfused in vitro and reduced brush-border membrane vesicle NaPi-2a protein abundance from renal cortex incubated in vitro with PGE2. In conclusion, FGF-23 increases urinary and renal tubular PGE2 production via the MAP kinase pathway and PGE2 inhibits proximal tubule phosphate transport. PMID:16144964

Adhesion, biofilm and genotypic characteristics of antimicrobial resistant Escherichia coli isolates.

PubMed

Cergole-Novella, Maria C; Pignatari, Antonio C C; Guth, Beatriz E C

2015-03-01

Aggregative adherence to human epithelial cells, most to renal proximal tubular (HK-2) cells, and biofilm formation was identified among antimicrobial resistant Escherichia coli strains mainly isolated from bacteremia. The importance of these virulence properties contributing to host colonization and infection associated with multiresistant E. coli should not be neglected.

Importance of inhibiting sodium-glucose cotransporter and its compelling indication in type 2 diabetes: pathophysiological hypothesis.

PubMed

Kimura, Genjiro

2016-03-01

Primarily the sodium-glucose cotransporter 2 (SGLT2) inhibitors suppress the cotransport of glucose and sodium from the tubular lumen of proximal tubules to the blood and enhance the glucose excretion into urine. Therefore, glucose and caloric balances become negative, making the blood glucose level as well as insulin secretion both reduced. On the other hand, the proximal tubular fluid, constituting with low chloride concentration because of SGLT2 inhibition, is transferred to the loop of Henle. On the low chloride conditions, the reabsorption mechanisms in the loop of Henle do not work, as if loop diuretics are given. Finally, blood pressure is also lowered secondarily due to the loop diuretic action by SGLT2 inhibitions. Thus, the metabolic and hemodynamic combined systems synergistically interact further to suppress the risks leading to atherosclerosis and organs damage. Precise mechanisms for SGLT2 inhibitors to work in various aspects especially in preventing organ damage and cardiovascular events must be clarified further. Copyright © 2016 American Society of Hypertension. Published by Elsevier Inc. All rights reserved.

Pathophysiology of Cisplatin-Induced Acute Kidney Injury

PubMed Central

Ozkok, Abdullah; Edelstein, Charles L.

2014-01-01

Cisplatin and other platinum derivatives are the most widely used chemotherapeutic agents to treat solid tumors including ovarian, head and neck, and testicular germ cell tumors. A known complication of cisplatin administration is acute kidney injury (AKI). The nephrotoxic effect of cisplatin is cumulative and dose-dependent and often necessitates dose reduction or withdrawal. Recurrent episodes of AKI may result in chronic kidney disease. The pathophysiology of cisplatin-induced AKI involves proximal tubular injury, oxidative stress, inflammation, and vascular injury in the kidney. There is predominantly acute tubular necrosis and also apoptosis in the proximal tubules. There is activation of multiple proinflammatory cytokines and infiltration of inflammatory cells in the kidney. Inhibition of the proinflammatory cytokines TNF-α or IL-33 or depletion of CD4+ T cells or mast cells protects against cisplatin-induced AKI. Cisplatin also causes endothelial cell injury. An understanding of the pathogenesis of cisplatin-induced AKI is important for the development of adjunctive therapies to prevent AKI, to lessen the need for dose decrease or drug withdrawal, and to lessen patient morbidity and mortality. PMID:25165721

SGLT2 Inhibitors and the Diabetic Kidney.

PubMed

Fioretto, Paola; Zambon, Alberto; Rossato, Marco; Busetto, Luca; Vettor, Roberto

2016-08-01

Diabetic nephropathy (DN) is the most common cause of end-stage renal disease worldwide. Blood glucose and blood pressure control reduce the risk of developing this complication; however, once DN is established, it is only possible to slow progression. Sodium-glucose cotransporter 2 (SGLT2) inhibitors, the most recent glucose-lowering oral agents, may have the potential to exert nephroprotection not only through improving glycemic control but also through glucose-independent effects, such as blood pressure-lowering and direct renal effects. It is important to consider, however, that in patients with impaired renal function, given their mode of action, SGLT2 inhibitors are less effective in lowering blood glucose. In patients with high cardiovascular risk, the SGLT2 inhibitor empagliflozin lowered the rate of cardiovascular events, especially cardiovascular death, and substantially reduced important renal outcomes. Such benefits on DN could derive from effects beyond glycemia. Glomerular hyperfiltration is a potential risk factor for DN. In addition to the activation of the renin-angiotensin-aldosterone system, renal tubular factors, including SGLT2, contribute to glomerular hyperfiltration in diabetes. SGLT2 inhibitors reduce sodium reabsorption in the proximal tubule, causing, through tubuloglomerular feedback, afferent arteriole vasoconstriction and reduction in hyperfiltration. Experimental studies showed that SGLT2 inhibitors reduced hyperfiltration and decreased inflammatory and fibrotic responses of proximal tubular cells. SGLT2 inhibitors reduced glomerular hyperfiltration in patients with type 1 diabetes, and in patients with type 2 diabetes, they caused transient acute reductions in glomerular filtration rate, followed by a progressive recovery and stabilization of renal function. Interestingly, recent studies consistently demonstrated a reduction in albuminuria. Although these data are promising, only dedicated renal outcome trials will clarify whether SGLT2 inhibitors, in addition to their glycemic and blood pressure benefits, may provide nephroprotective effects. © 2016 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

A case of severe osteomalacia caused by Tubulointerstitial nephritis with Fanconi syndrome in asymptomotic primary biliary cirrhosis.

PubMed

Yamaguchi, Shintaro; Maruyama, Tatsuya; Wakino, Shu; Tokuyama, Hirobumi; Hashiguchi, Akinori; Tada, Shinichiro; Homma, Koichiro; Monkawa, Toshiaki; Thomas, James; Miyashita, Kazutoshi; Kurihara, Isao; Yoshida, Tadashi; Konishi, Konosuke; Hayashi, Koichi; Hayashi, Matsuhiko; Itoh, Hiroshi

2015-11-11

Primary biliary cirrhosis (PBC) is an immune-mediated chronic cholestatic liver disease, characterized by increased concentrations of serum IgM and the presence of circulating anti-mitochondrial antibodies. Although bone diseases such as osteoporosis or osteodystrophy are commonly associated with PBC, osteomalacia which is caused by abnormal vitamin D metabolism, mineralization defects, and phosphate deficiency has not been recognized as a complication of PBC. We report the case of a 49-year-old Japanese woman who complained of multiple fractures. Hypophosphatemic osteomalacia was diagnosed from a low serum phosphorus level, 1,25-dihydroxyvitamin D3 level, high levels of bone specific alkaline phosphatase and the findings of bone scintigraphy, although a bone biopsy was not performed. Twenty four hour urine demonstrated a low renal fractional tubular reabsorption of phosphate, increased fractional excretion of uric acid and generalized aminoaciduria. An intravenous bicarbonate loading test suggested the presence of proximal renal tubular acidosis (RTA). These biochemical data indicated Fanconi syndrome with proximal RTA. A kidney biopsy demonstrated the features of tubulointerstitial nephritis (TIN). The patient was also suspected as having primary biliary cirrhosis (PBC) because of high levels of alkaline phosphatase, IgM and the presence of anti-mitochondrial M2 antibody, though biochemical liver function was normal. Sequential liver biopsy was compatible with PBC and the diagnosis of PBC was definite. After administration of 1,25 dihydroxyvitamin D3, neutral potassium phosphate, sodium bicarbonate for osteomalacia and subsequent predonizolone for TIN, symptoms of fractures were relieved and renal function including Fanconi syndrome was ameliorated. In this case, asymptomatic PBC was shown to induce TIN with Fanconi syndrome with dysregulation of electrolytes and vitamin D metabolism, which in turn led to osteomalacia with multiple fractures. Osteomalacia has not been recognized as a result of the renal involvement of PBC. PBC and its rare complication of TIN with Fanconi syndrome should be considered in adult patients with unexplained osteomalacia even in the absence of liver dysfunction.

Trans-proximal tubular steady-state concentration differences studied by micro-puncture and tissue content of sodium and chloride at varying intraluminal sodium concentrations in vitro in rat kidney cortex slices: evidence for a multisite sodium transport system.

PubMed Central

Györy, A Z; Roby, H

1977-01-01

1. With the aid of micropuncture techniques, proximal tubular transepithelial concentration differences for Na (deltaC Na) and chloride (deltaC Cl) were measured in kidney cortex slices at bathing fluid Na concentrations from 10 to 400 m-mole. kg-1. Tissue content of water, Na and K was also measured in such slices. Under steady-state conditions of zero net flux of NaCl and water, deltaC Na represents the sum of active Na transport, factored by the tubular permeability coefficient added to a component of flux due to electrical forces. 2. The relation between bathing fluid Na concentraton and deltaC Na appeared sigmoid in form suggesting an allosteric mechanism for the transport step. 3. Transtubular potential difference, calculated from transepithelial Cl distribution ratios, did not appear constant at the various bathing fluid Na concentrations. Correcting for the effect of these potential differences on the value of each deltaC Na did not convert the sigmoid transport curve to a hyperbolic one, confirming the suggested allosteric nature of the active Na transport step. 4. Intracellular Na content varied linearly with bathing fluid Na concentrations implying free entry of this cation into the cell. This also suggests that the sigmoid transport curve is related to the properties of the active Na transport pump. PMID:856986

[Study on the assay of proximal tubular antigen in urine and serum with an anti-human renal monoclonal antibody].

PubMed

Taniai, K

1991-10-01

Monoclonal antibodies (Mabs) were produced by immunizing mice with human kidney microsomal antigen. Mab-B1 recognized brushborder (B1-Ag) in proximal tubules. Using Mab-B1, B1-Ag was assayed in the urine and serum of renal disease patients by sandwich ELISA. The subjects included normal control (Nor), minimal change nephrotic syndrome (MCNS), IgA nephropathy (IgA), membranous nephropathy (MN), membranoproliferative glomerulonephritis (MPGN), and chronic renal failure (CRF) (s-Cr greater than 2 mg/dl). Urinary B1-Ag demonstrated significant increases in the IgA (p less than 0.001), MN (p less than 0.001), MPGN (p less than 0.001) and CRF (p less than 0.01) groups as compared to the Nor group. There was no significant increase in the MCNS group. In the CRF group, B1-Ag in urine showed a significant increase in the progressive CRF group with delta s-Cr greater than 1.0 mg/dl/month as compared to the stationary CRF group with delta s-Cr less than 1.0 mg/dl/month. No correlation was observed between urinary B1-Ag and proteinuria, hematuria, s-Cr, s-BMG and u-NAG. The above findings suggested that the assay of urinary B1-Ag was useful as a new parameter in detecting the site and degree of proximal tubular damage.

Characterization of Organic Anion Transporter 2 (SLC22A7): A Highly Efficient Transporter for Creatinine and Species-Dependent Renal Tubular Expression.

PubMed

Shen, Hong; Liu, Tongtong; Morse, Bridget L; Zhao, Yue; Zhang, Yueping; Qiu, Xi; Chen, Cliff; Lewin, Anne C; Wang, Xi-Tao; Liu, Guowen; Christopher, Lisa J; Marathe, Punit; Lai, Yurong

2015-07-01

The contribution of organic anion transporter OAT2 (SLC22A7) to the renal tubular secretion of creatinine and its exact localization in the kidney are reportedly controversial. In the present investigation, the transport of creatinine was assessed in human embryonic kidney (HEK) cells that stably expressed human OAT2 (OAT2-HEK) and isolated human renal proximal tubule cells (HRPTCs). The tubular localization of OAT2 in human, monkey, and rat kidney was characterized. The overexpression of OAT2 significantly enhanced the uptake of creatinine in OAT2-HEK cells. Under physiologic conditions (creatinine concentrations of 41.2 and 123.5 µM), the initial rate of OAT2-mediated creatinine transport was approximately 11-, 80-, and 80-fold higher than OCT2, multidrug and toxin extrusion protein (MATE)1, and MATE2K, respectively, resulting in approximately 37-, 1850-, and 80-fold increase of the intrinsic transport clearance when normalized to the transporter protein concentrations. Creatinine intracellular uptake and transcellular transport in HRPTCs were decreased in the presence of 50 µM bromosulfophthalein and 100 µM indomethacin, which inhibited OAT2 more potently than other known creatinine transporters, OCT2 and multidrug and toxin extrusion proteins MATE1 and MATE2K (IC50: 1.3 µM vs. > 100 µM and 2.1 µM vs. > 200 µM for bromosulfophthalein and indomethacin, respectively) Immunohistochemistry analysis showed that OAT2 protein was localized to both basolateral and apical membranes of human and cynomolgus monkey renal proximal tubules, but appeared only on the apical membrane of rat proximal tubules. Collectively, the findings revealed the important role of OAT2 in renal secretion and possible reabsorption of creatinine and suggested a molecular basis for potential species difference in the transporter handling of creatinine. Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.

Interferon-γ biphasically regulates angiotensinogen expression via a JAK-STAT pathway and suppressor of cytokine signaling 1 (SOCS1) in renal proximal tubular cells

PubMed Central

Satou, Ryousuke; Miyata, Kayoko; Gonzalez-Villalobos, Romer A.; Ingelfinger, Julie R.; Navar, L. Gabriel; Kobori, Hiroyuki

2012-01-01

Renal inflammation modulates angiotensinogen (AGT) production in renal proximal tubular cells (RPTCs) via inflammatory cytokines, including interleukin-6, tumor necrosis factor α, and interferon-γ (IFN-γ). Among these, the effects of IFN-γ on AGT regulation in RPTCs are incompletely delineated. This study aimed to elucidate mechanisms by which IFN-γ regulates AGT expression in RPTCs. RPTCs were incubated with or without IFN-γ up to 48 h. AGT expression, STAT1 and STAT3 activities, and SOCS1 expression were evaluated. RNA interference studies against STAT1, SOCS1, and STAT3 were performed to elucidate a signaling cascade. IFN-γ decreased AGT expression at 6 h (0.61±0.05, ratio to control) and 12 h (0.47±0.03). In contrast, longer exposure for 24 and 48 h increased AGT expression (1.76±0.18, EC50=3.4 ng/ml, and 1.45±0.08, respectively). IFN-γ treatment for 6 h strongly induced STAT1 phosphorylation and SOCS1 augmentation, and decreased STAT3 activity. However, STAT1 phosphorylation and SOCS1 augmentation waned at 24 h, while STAT3 activity increased. RNA interference studies revealed that activation of STAT1-SOCS1 axis decreased STAT3 activity. Thus, IFN-γ biphasically regulates AGT expression in RPTCs via STAT3 activity modulated by STAT1-SOCS1 axis, suggesting the STAT1-SOCS1 axis is important in IFN-γ-induced activation of the intrarenal renin-angiotensin system.—Satou, R., Miyata, K., Gonzalez-Villalobos, R. A., Ingelfinger, J. R., Navar, L. G., Kobori, H. Interferon-γ biphasically regulates angiotensinogen expression via a JAK-STAT pathway and suppressor of cytokine signaling 1 (SOCS1) in renal proximal tubular cells. PMID:22302831

Telmisartan, a possible PPAR-δ agonist, reduces TNF-α-stimulated VEGF-C production by inhibiting the p38MAPK/HSP27 pathway in human proximal renal tubular cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kimura, Hideki, E-mail: hkimura@u-fukui.ac.jp; Department of Clinical Laboratories and Nephrology, University of Fukui Hospital, Fukui; Mikami, Daisuke

Highlights: • TNF-α increased VEGF-C expression by enhancing phosphorylation of p38MAPK and HSP27. • Telmisartan decreased TNF-α-stimulated expression of VEGF-C. • Telmisartan suppressed TNF-α-induced phosphorylation of p38MAPK and HSP27. • Telmisartan activated endogenous PPAR-δ protein. • Telmisartan suppressed p38MAPK phosphorylation in a PPAR-δ-dependent manner. - Abstract: Vascular endothelial growth factor-C (VEGF-C) is a main inducer of inflammation-associated lymphangiogenesis in various inflammatory disorders including chronic progressive kidney diseases, for which angiotensin II receptor type 1 blockers (ARBs) are widely used as the main treatment. Although proximal renal tubular cells may affect the formation of lymphatic vessels in the interstitial area bymore » producing VEGF-C, the molecular mechanisms of VEGF-C production and its manipulation by ARB have not yet been examined in human proximal renal tubular epithelial cells (HPTECs). In the present study, TNF-α dose-dependently induced the production of VEGF-C in HPTECs. The TNF-α-induced production of VEGF-C was mediated by the phosphorylation of p38MAPK and HSP27, but not by that of ERK or NFkB. Telmisartan, an ARB that can activate the peroxisome proliferator-activated receptor (PPAR), served as a PPAR-δ activator and reduced the TNF-α-stimulated production of VEGF-C. This reduction was partially attributed to a PPAR-δ-dependent decrease in p38MAPK phosphorylation. Our results indicate that TNF-α induced the production of VEGF-C in HPTECs by activating p38MAPK/HSP27, and this was partially inhibited by telmisartan in a PPAR-δ dependent manner. These results provide a novel insight into inflammation-associated lymphangiogenesis.« less

Elevated ventricular wall stress disrupts cardiomyocyte t-tubule structure and calcium homeostasis.

PubMed

Frisk, Michael; Ruud, Marianne; Espe, Emil K S; Aronsen, Jan Magnus; Røe, Åsmund T; Zhang, Lili; Norseng, Per Andreas; Sejersted, Ole M; Christensen, Geir A; Sjaastad, Ivar; Louch, William E

2016-10-01

Invaginations of the cellular membrane called t-tubules are essential for maintaining efficient excitation-contraction coupling in ventricular cardiomyocytes. Disruption of t-tubule structure during heart failure has been linked to dyssynchronous, slowed Ca(2+) release and reduced power of the heartbeat. The underlying mechanism is, however, unknown. We presently investigated whether elevated ventricular wall stress triggers remodelling of t-tubule structure and function. MRI and blood pressure measurements were employed to examine regional wall stress across the left ventricle of sham-operated and failing, post-infarction rat hearts. In failing hearts, elevated left ventricular diastolic pressure and ventricular dilation resulted in markedly increased wall stress, particularly in the thin-walled region proximal to the infarct. High wall stress in this proximal zone was associated with reduced expression of the dyadic anchor junctophilin-2 and disrupted cardiomyocyte t-tubular structure. Indeed, local wall stress measurements predicted t-tubule density across sham and failing hearts. Elevated wall stress and disrupted cardiomyocyte structure in the proximal zone were also associated with desynchronized Ca(2+) release in cardiomyocytes and markedly reduced local contractility in vivo. A causative role of wall stress in promoting t-tubule remodelling was established by applying stretch to papillary muscles ex vivo under culture conditions. Loads comparable to wall stress levels observed in vivo in the proximal zone reduced expression of junctophilin-2 and promoted t-tubule loss. Elevated wall stress reduces junctophilin-2 expression and disrupts t-tubule integrity, Ca(2+) release, and contractile function. These findings provide new insight into the role of wall stress in promoting heart failure progression. © The Author 2016. Published by Oxford University Press on behalf of the European Society of Cardiology.

FGF23 regulates renal sodium handling and blood pressure

PubMed Central

Andrukhova, Olena; Slavic, Svetlana; Smorodchenko, Alina; Zeitz, Ute; Shalhoub, Victoria; Lanske, Beate; Pohl, Elena E; Erben, Reinhold G

2014-01-01

Fibroblast growth factor-23 (FGF23) is a bone-derived hormone regulating renal phosphate reabsorption and vitamin D synthesis in renal proximal tubules. Here, we show that FGF23 directly regulates the membrane abundance of the Na+:Cl− co-transporter NCC in distal renal tubules by a signaling mechanism involving the FGF receptor/αKlotho complex, extracellular signal-regulated kinase 1/2 (ERK1/2), serum/glucocorticoid-regulated kinase 1 (SGK1), and with-no lysine kinase-4 (WNK4). Renal sodium (Na+) reabsorption and distal tubular membrane expression of NCC are reduced in mouse models of Fgf23 and αKlotho deficiency. Conversely, gain of FGF23 function by injection of wild-type mice with recombinant FGF23 or by elevated circulating levels of endogenous Fgf23 in Hyp mice increases distal tubular Na+ uptake and membrane abundance of NCC, leading to volume expansion, hypertension, and heart hypertrophy in a αKlotho and dietary Na+-dependent fashion. The NCC inhibitor chlorothiazide abrogates FGF23-induced volume expansion and heart hypertrophy. Our findings suggest that FGF23 is a key regulator of renal Na+ reabsorption and plasma volume, and may explain the association of FGF23 with cardiovascular risk in chronic kidney disease patients. PMID:24797667

Optical coherence tomography and computer-aided diagnosis of a murine model of chronic kidney disease

NASA Astrophysics Data System (ADS)

Wang, Bohan; Wang, Hsing-Wen; Guo, Hengchang; Anderson, Erik; Tang, Qinggong; Wu, Tongtong; Falola, Reuben; Smith, Tikina; Andrews, Peter M.; Chen, Yu

2017-12-01

Chronic kidney disease (CKD) is characterized by a progressive loss of renal function over time. Histopathological analysis of the condition of glomeruli and the proximal convolutional tubules over time can provide valuable insights into the progression of CKD. Optical coherence tomography (OCT) is a technology that can analyze the microscopic structures of a kidney in a nondestructive manner. Recently, we have shown that OCT can provide real-time imaging of kidney microstructures in vivo without administering exogenous contrast agents. A murine model of CKD induced by intravenous Adriamycin (ADR) injection is evaluated by OCT. OCT images of the rat kidneys have been captured every week up to eight weeks. Tubular diameter and hypertrophic tubule population of the kidneys at multiple time points after ADR injection have been evaluated through a fully automated computer-vision system. Results revealed that mean tubular diameter and hypertrophic tubule population increase with time in post-ADR injection period. The results suggest that OCT images of the kidney contain abundant information about kidney histopathology. Fully automated computer-aided diagnosis based on OCT has the potential for clinical evaluation of CKD conditions.

Experimental investigation of the structural behavior of equine urethra.

PubMed

Natali, Arturo Nicola; Carniel, Emanuele Luigi; Frigo, Alessandro; Fontanella, Chiara Giulia; Rubini, Alessandro; Avital, Yochai; De Benedictis, Giulia Maria

2017-04-01

An integrated experimental and computational investigation was developed aiming to provide a methodology for characterizing the structural response of the urethral duct. The investigation provides information that are suitable for the actual comprehension of lower urinary tract mechanical functionality and the optimal design of prosthetic devices. Experimental activity entailed the execution of inflation tests performed on segments of horse penile urethras from both proximal and distal regions. Inflation tests were developed imposing different volumes. Each test was performed according to a two-step procedure. The tubular segment was inflated almost instantaneously during the first step, while volume was held constant for about 300s to allow the development of relaxation processes during the second step. Tests performed on the same specimen were interspersed by 600s of rest to allow the recovery of the specimen mechanical condition. Results from experimental activities were statistically analyzed and processed by means of a specific mechanical model. Such computational model was developed with the purpose of interpreting the general pressure-volume-time response of biologic tubular structures. The model includes parameters that interpret the elastic and viscous behavior of hollow structures, directly correlated with the results from the experimental activities. Post-processing of experimental data provided information about the non-linear elastic and time-dependent behavior of the urethral duct. In detail, statistically representative pressure-volume and pressure relaxation curves were identified, and summarized by structural parameters. Considering elastic properties, initial stiffness ranged between 0.677 ± 0.026kPa and 0.262 ± 0.006kPa moving from proximal to distal region of penile urethra. Viscous parameters showed typical values of soft biological tissues, as τ 1 =0.153±0.018s, τ 2 =17.458 ± 1.644s and τ 1 =0.201 ± 0.085, τ 2 = 8.514 ± 1.379s for proximal and distal regions respectively. A general procedure for the mechanical characterization of the urethral duct has been provided. The proposed methodology allows identifying mechanical parameters that properly express the mechanical behavior of the biological tube. The approach is especially suitable for evaluating the influence of degenerative phenomena on the lower urinary tract mechanical functionality. The information are mandatory for the optimal design of potential surgical procedures and devices. Copyright © 2017 Elsevier B.V. All rights reserved.

An atypical pattern of Epstein-Barr virus infection in a case with idiopathic tubulointerstitial nephritis.

PubMed

Okada, Hirokazu; Ikeda, Naofumi; Kobayashi, Tatsuya; Inoue, Tsutomu; Kanno, Yoshihiko; Sugahara, Souichi; Nakamoto, Hidetomo; Yamamoto, Takako; Suzuki, Hiromichi

2002-10-01

Recently, Epstein-Barr virus (EBV) received attention because a latent form of its infection in renal proximal tubular epithelial cells was found to cause idiopathic, chronic tubulointerstitial nephritis. In this report, we describe the case of a patient with a replicative form of EBV infection, chronic active EBV infection (CAEBV), who developed acute tubulointerstitial nephritis and minimal change nephrotic syndrome. A renal biopsy revealed papillary infoldings of atypical tubular epithelium and adjacent dense infiltration of lymphocytes. Using in situ polymerase chain reaction methods, we detected the EBV genome in some of the infiltrating lymphocytes, but not in the tubular epithelial cells. EBV-infected T cells are thought to activate other educated T cells, as well as secrete an unrestricted variety of cytokines, thus playing a pivotal role in CAEBV and its end organ disease. Therefore, in our case, the CAEBV activated, educated T cells may have followed the EBV-infected lymphocytes as they infiltrated into the peritubular interstitium, and promoted focal tubular epithelial atypia and minimal change nephrotic syndrome. The long-term observation of such patients is important because CAEBV may progress into lymphoproliferative diseases. Copyright 2002 S. Karger AG, Basel

Retention of differentiated characteristics by cultures of defined rabbit kidney epithelia.

PubMed

Wilson, P D; Anderson, R J; Breckon, R D; Nathrath, W; Schrier, R W

1987-02-01

Rabbit nephron segments of proximal convoluted tubules (PCT); proximal straight tubules (PST); cortical and medullary thick ascending limbs of Henle's loop (CAL, MAL); and cortical, outer medullary, and inner medullary collecting tubules (CCT, OMCT, IMCT) were individually microdissected and grown in monolayer culture in hormone supplemented, defined media. Factors favoring a rapid onset of proliferation included young donor age, distal tubule origin, and the addition of 3% fetal calf serum to the medium. All primary cultures had polarized morphology with apical microvilli facing the medium and basement membrane-like material adjacent to the dish. Differentiated properties characteristic of the tubular epithelium of origin retained in cultures included ultrastructural characteristics and cytochemically demonstrable marker enzyme proportions. PCT and PST were rich in alkaline phosphatase; CAL stained strongly for NaK-ATPase; CCT contained two cell populations with regard to cytochrome oxidase reaction. A CCT-specific anti-keratin antibody (aLEA) was immunolocalized in CCT cultures, and a PST cytokeratin antibody stained PST cultures. The biochemical response of adenylate cyclase to putative stimulating agents was the same in primary cultures as in freshly isolated tubules. In PCT and PST adenylate cyclase activity was stimulated by parathyroid hormone (PTH) but not by arginine vasopressin (AVP); CAL and MAL adenylate cyclase was stimulated by neither PTH nor AVP; CCT, OMCT, and IMCT adenylate cyclase was stimulated by AVP but not by PTH. NaF stimulated adenylate cyclase activity in every cultured segment. It is concluded that primary cultures of individually microdissected rabbit PCT, PST, CAL, MAL, CCT, OMCT, and IMCT retain differentiated characteristics with regard to ultrastructure, marker enzymes, cytoskeletal proteins, and hormone response of adenylate cyclase and provide a new system for studying normal and abnormal functions of the heterogeneous tubular epithelia in the kidney.

Combination of direct renin inhibition with angiotensin type 1 receptor blockade improves aldosterone but does not improve kidney injury in the transgenic Ren2 rat.

PubMed

Whaley-Connell, Adam; Habibi, Javad; Nistala, Ravi; Hayden, Melvin R; Pulakat, Lakshmi; Sinak, Catherine; Locher, Bonnie; Ferrario, Carlos M; Sowers, James R

2012-06-10

Enhanced renin-angiotensin-aldosterone system (RAAS) activation contributes to proteinuria and chronic kidney disease by increasing glomerular and tubulointerstitial oxidative stress, promotion of fibrosis. Renin activation is the rate limiting step in angiotensin (Ang II) and aldosterone generation, and recent work suggests direct renin inhibition improves proteinuria comparable to that seen with Ang type 1 receptor (AT(1)R) blockade. This is important as, even with contemporary use of AT(1)R blockade, the burden of kidney disease remains high. Thereby, we sought to determine if combination of direct renin inhibition with AT(1)R blockade in vivo, via greater attenuation of kidney oxidative stress, would attenuate glomerular and proximal tubule injury to a greater extent than either intervention alone. We utilized the transgenic Ren2 rat with increased tissue RAS activity and higher serum levels of aldosterone, which manifests hypertension and proteinuria. Ren2 rats were treated with renin inhibition (aliskiren), AT(1)R blockade (valsartan), the combination (aliskiren+valsartan), or vehicle for 21days. Compared to Sprague-Dawley controls, Ren2 rats displayed increased systolic pressure (SBP), circulating aldosterone, proteinuria and greater urine levels of the proximal tubule protein excretory marker beta-N-acetylglucosaminidase (β-NAG). These functional and biochemical alterations were accompanied by increases in kidney tissue NADPH oxidase subunit Rac1 and 3-nitrotyrosine (3-NT) content as well as fibronectin and collagen type III. These findings occurred in conjunction with reductions in the podocyte-specific protein podocin as well as the proximal tubule-specific megalin. Further, in transgenic animals there was increased tubulointerstitial fibrosis on light microscopy as well as ultrastructural findings of glomerular podocyte foot-process effacement and reduced tubular apical endosomal/lysosomal activity. Combination therapy led to greater reductions in SBP and serum aldosterone, but did not result in greater improvement in markers of glomerular and tubular injury (i.e. β-NAG) compared to either intervention alone. Further, combination therapy did not improve markers of oxidative stress and podocyte and proximal tubule integrity in this transgenic model of RAAS-mediated kidney damage despite greater reductions in serum aldosterone and BP levels. Published by Elsevier B.V.

Creatinine reabsorption by the aged kidney.

PubMed

Musso, Carlos G; Michelángelo, Hernán; Vilas, Manuel; Reynaldi, Juliana; Martinez, Bernardo; Algranati, Luis; Macías Núñez, Juan F

2009-01-01

The handling of renal creatinine in human beings has classically been described as the result of two particular physiological processes: glomerular filtration and proximal tubular secretion. However, there are particular physiological situations in which tubular creatinine reabsorption has been documented, such as in the case of healthy newborns and premature babies. We performed a prospective study in order to evaluate if there is tubular creatinine reabsorption in healthy elderly people. We studied prospectively nine healthy volunteers, four of them young (20-33 years old) and the remaining five, old (65-73 years old). Since creatinine is secreted in the proximal tubules, and its secretion can be completely blocked by cimetidine administration, a creatinine clearance with cimetidine reliably represents the glomerular filtration rate. Therefore, if the ratio creatinine clearance (Ccr)/creatinine clearance with cimetidine (CcrWC) is higher than one, this would indicate net creatinine secretion, whereas a ratio lower than one would indicate a net renal creatinine tubular reabsorption; a ratio equal to one indicates creatinine filtration. Finally, the Ccr, CcrWC, and Ccr/CcrWC ratios were compared between the young and old group. Mann-Whitney and Wilcoxon tests were used. As expected, creatinine clearance in the elderly was significantly lower than in the young [Ccr: 74.4 ml/min (47.9-100.9) (old) vs. 153.8 ml/min (108.3-199.2) (young), p = 0.014]. Similarly, the creatinine clearance with cimetidine (CcrWC) was significantly lower in the elderly compared to the young [CcrWC: 81.8 ml/min (69.2-94.5) (old) vs. 122.5 ml/min (82.6-162.4) (young), p = 0.028]. The ratio of Ccr/CcrWC was 0.9 in the elderly vs. 1.26 in the young (p = 0.014), indicating net creatinine reabsorption in the elderly and net creatinine secretion in the young. Our findings indicate that there seems to be a net reabsorption of creatinine in the renal tubules of healthy old persons.

The 6-hydroxychromanol derivative SUL-109 ameliorates renal injury after deep hypothermia and rewarming in rats.

PubMed

Vogelaar, Pieter C; Roorda, Maurits; de Vrij, Edwin L; Houwertjes, Martin C; Goris, Maaike; Bouma, Hjalmar; van der Graaf, Adrianus C; Krenning, Guido; Henning, Robert H

2018-04-11

Mitochondrial dysfunction plays an important role in kidney damage in various pathologies, including acute and chronic kidney injury and diabetic nephropathy. In addition to the well-studied ischaemia/reperfusion (I/R) injury, hypothermia/rewarming (H/R) also inflicts acute kidney injury. Substituted 6-hydroxychromanols are a novel class of mitochondrial medicines that ameliorate mitochondrial oxidative stress and protect the mitochondrial network. To identify a novel 6-hydroxychromanol that protects mitochondrial structure and function in the kidney during H/R, we screened multiple compounds in vitro and subsequently assessed the efficacy of the 6-hydroxychromanol derivatives SUL-109 and SUL-121 in vivo to protect against kidney injury after H/R in rats. Human proximal tubule cell viability was assessed following exposure to H/R for 48/4 h in the presence of various 6-hydroxychromanols. Selected compounds (SUL-109, SUL-121) or vehicle were administered to ketamine-anaesthetized male Wistar rats (IV 135 µg/kg/h) undergoing H/R at 15°C for 3 h followed by rewarming and normothermia for 1 h. Metabolic parameters and body temperature were measured throughout. In addition, renal function, renal injury, histopathology and mitochondrial fitness were assessed. H/R injury in vitro lowered cell viability by 94 ± 1%, which was counteracted dose-dependently by multiple 6-hydroxychomanols derivatives. In vivo, H/R in rats showed kidney injury molecule 1 expression in the kidney and tubular dilation, accompanied by double-strand DNA breaks and protein nitrosylation. SUL-109 and SUL-121 ameliorated tubular kidney damage, preserved mitochondrial mass and maintained cortical adenosine 5'-triphosphate (ATP) levels, although SUL-121 did not reduce protein nitrosylation. The substituted 6-hydroxychromanols SUL-109 and SUL-121 ameliorate kidney injury during in vivo H/R by preserving mitochondrial mass, function and ATP levels. In addition, both 6-hydroxychromanols limit DNA damage, but only SUL-109 also prevented protein nitrosylation in tubular cells. Therefore SUL-109 offers a promising therapeutic strategy to preserve kidney mitochondrial function.

[Effect of Cordyceps sinensis on the expression of HIF-1α and NGAL in rats with renal ischemia-reperfusion injury].

PubMed

Yu, Honglei; Zhou, Qiaoling; Huang, Renfa; Yuan, Mingxia; Ao, Xiang; Yang, Jinghua

2012-01-01

To observe the level of urinary neutrophil gelatinase-associated lipocalin (NGAL), the expression of hypoxia inducible factor-1α (HIF-1α) and NGAL in rat kidney after renal ischemia and reperfusion (I/R), before and after the treatment with Cordyceps Sinensis (C. sinensis), and to explore the mechanism of C. sinensis against I/R injury. A total of 45 healthy male Sprague-Dawley rats were randomly divided into a sham group, a renal I/R model group, and a C. sinensis group (15 in each group).The rats in the sham group and the renal I/R model group were intragastrically administered saline (2 mL/d), and rats in the treatment group were intragastricabby administered of C. sinensis [5.0 g/(kg.d)]. The rats were sacrificed at 24, 48, and 72 h, respectively after the reperfusion and urinary N-acetyl-β-D-glucosaminidase (NAG) level was measured, renal function in rats was detected, and the pathological changes were observed with HE staining. We determined the urinary NGAL levels in the rats by ELISA, the expression of HIF-1α mRNA by RT-PCR, and the expressions of HIF-1α and NGAL proteins by confocal immunofluorescence. Compared with the sham group, the levels of BUN, SCr, levels of NAG and NGAL in urine were increased in the I/R group and the C. sinensis group, reached a peak at 24 h after the reperfusion and slowly declined at 48 and 72 h. Glomerular and tubulointerstitial areas in the sham group did not show any pathological change. Induced pathological changes included tubular cell necrosis, focal areas of proximal tubular dilation, distal tubular casts, effacement and loss of proximal tubule brush border, etc. Compared with the sham group, the expression of HIF-1α and NGAL in the kidney tissues of the I/R group and the C. sinensis group increased. C. sinensis can lower the level of NAG and NGAL in the urine and the expression of NGAL protein in the kidney tissues. It up-regulated the expression of HIF-1α mRNA and protein in the kidney tissues whilst attenuated the pathological changes. Renal I/R injury in rats can lead to pathological changes in renal tubular epithelial cells and renal interstitial damage, which are consistent with the pathological features of acute kidney injury (AKI).The level of urinary NAGL increases after the I/R, and positively correlates with the level of urinary NAG and pathological changes, suggesting that urinary NGAL may serve as a urinary biomarker for specific detection of tubular injury in AKI. C. sinensis can attenuate the renal I/ R-induced AKI. Its mechanism may be associated with up-regulating the expression of HIF-1α and down-regulating the expression of NGAL in the kidney tissues.

Congenital myasthenic syndrome with tubular aggregates caused by GFPT1 mutations.

PubMed

Guergueltcheva, Velina; Müller, Juliane S; Dusl, Marina; Senderek, Jan; Oldfors, Anders; Lindbergh, Christopher; Maxwell, Susan; Colomer, Jaume; Mallebrera, Cecilia Jimenez; Nascimento, Andres; Vilchez, Juan J; Muelas, Nuria; Kirschner, Janbernd; Nafissi, Shahriar; Kariminejad, Ariana; Nilipour, Yalda; Bozorgmehr, Bita; Najmabadi, Hossein; Rodolico, Carmelo; Sieb, Jörn P; Schlotter, Beate; Schoser, Benedikt; Herrmann, Ralf; Voit, Thomas; Steinlein, Ortrud K; Najafi, Abdolhamid; Urtizberea, Andoni; Soler, Doriette M; Muntoni, Francesco; Hanna, Michael G; Chaouch, Amina; Straub, Volker; Bushby, Kate; Palace, Jacqueline; Beeson, David; Abicht, Angela; Lochmüller, Hanns

2012-05-01

Congenital myasthenic syndrome (CMS) is a clinically and genetically heterogeneous group of inherited disorders of the neuromuscular junction. A difficult to diagnose subgroup of CMS is characterised by proximal muscle weakness and fatigue while ocular and facial involvement is only minimal. DOK7 mutations have been identified as causing the disorder in about half of the cases. More recently, using classical positional cloning, we have identified mutations in a previously unrecognised CMS gene, GFPT1, in a series of DOK7-negative cases. However, detailed description of clinical features of GFPT1 patients has not been reported yet. Here we describe the clinical picture of 24 limb-girdle CMS (LG-CMS) patients and pathological findings of 18 of them, all carrying GFPT1 mutations. Additional patients with CMS, but without tubular aggregates, and patients with non-fatigable weakness with tubular aggregates were also screened. In most patients with GFPT1 mutations, onset of the disease occurs in the first decade of life with characteristic limb-girdle weakness and fatigue. A common feature was beneficial and sustained response to acetylcholinesterase inhibitor treatment. Most of the patients who had a muscle biopsy showed tubular aggregates in myofibers. Analysis of endplate morphology in one of the patients revealed unspecific abnormalities. Our study delineates the phenotype of CMS associated with GFPT1 mutations and expands the understanding of neuromuscular junction disorders. As tubular aggregates in context of a neuromuscular transmission defect appear to be highly indicative, we suggest calling this condition congenital myasthenic syndrome with tubular aggregates (CMS-TA).

Cellular Uptake and Localization of Polymyxins in Renal Tubular Cells Using Rationally Designed Fluorescent Probes.

PubMed

Yun, Bo; Azad, Mohammad A K; Nowell, Cameron J; Nation, Roger L; Thompson, Philip E; Roberts, Kade D; Velkov, Tony; Li, Jian

2015-12-01

Polymyxins are cyclic lipopeptide antibiotics that serve as a last line of defense against Gram-negative bacterial superbugs. However, the extensive accumulation of polymyxins in renal tubular cells can lead to nephrotoxicity, which is the major dose-limiting factor in clinical use. In order to gain further insights into the mechanism of polymyxin-induced nephrotoxicity, we have rationally designed novel fluorescent polymyxin probes to examine the localization of polymyxins in rat renal tubular (NRK-52E) cells. Our design strategy focused on incorporating a dansyl fluorophore at the hydrophobic centers of the polymyxin core structure. To this end, four novel regioselectively labeled monodansylated polymyxin B probes (MIPS-9541, MIPS-9542, MIPS-9543, and MIPS-9544) were designed, synthesized, and screened for their antimicrobial activities and apoptotic effects against rat kidney proximal tubular cells. On the basis of the assessment of antimicrobial activities, cellular uptake, and apoptotic effects on renal tubular cells, incorporation of a dansyl fluorophore at either position 6 or 7 (MIPS-9543 and MIPS-9544, respectively) of the polymyxin core structure appears to be an appropriate strategy for generating representative fluorescent polymyxin probes to be utilized in intracellular imaging and mechanistic studies. Furthermore, confocal imaging experiments utilizing these probes showed evidence of partial colocalization of the polymyxins with both the endoplasmic reticulum and mitochondria in rat renal tubular cells. Our results highlight the value of these new fluorescent polymyxin probes and provide further insights into the mechanism of polymyxin-induced nephrotoxicity. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Enzymatic and histopathologic biomarkers as indicators of contaminant exposure and effect in Asian clam (Potamocorbula amurensis)

USGS Publications Warehouse

Teh, S.J.; Clark, S.L.; Brown, C.L.; Luoma, S.N.; Hinton, D.E.

1999-01-01

Enzymatic and histopathologic alterations of the digestive gland, gill, gonad, and kidney were studied in Asian clam (Potamocorbula amurensis) in April, 1997 from each of four United States Geological Survey (USGS) stations in the San Francisco Estuary. Stations were selected based on differing body burdens of metallic contaminants in clams (Stn 4.1>6.1>8.1>12.5) observed over 7 years. Because no pristine sites are known within the estuary and because no laboratory-reared stocks of P. amurensis were available, clams from station 12.5 served as reference animals. Histopathologic analysis revealed no lesions in clams collected from station 12.5. Mild digestive gland atrophy and moderate distal kidney tubular vacuolation were seen in clams collected from station 8.1. Mild digestive gland atrophy, moderate kidney tubular atrophy, and moderate gill inflammation were seen in clams collected from station 6.1. Lesions found only in clams from station 4.1 were: (1) severe inflammation and moderate atrophy of primary ducts and diverticula, and decreased numbers of heterophagosomes and heterolysosomes in diverticula of the digestive gland; (2) severe gill inflammation; (3) severe kidney tubular atrophy; (4) severe ovarian and testicular inflammation and necrosis (5) decreased numbers of mature ova; and (6) decreased number of glycogen storage cells in the ovary and testis. Localization of specific enzymes including adenosine triphosphatase (ATP), acid phosphatase (ACP), alkaline phosphatase (ALKP), gamma-glutamyl transpeptidase (GGT), and glucose-6-phosphate dehydrogenase (G6PDH) was performed and correlated, in serial sections with glycogen (PAS) and haematoxylin and eosin stains. Enzymatic analysis revealed: (1) increased digestive diverticula ATP in stations 6.1 and 4.1; (2) decreased digestive diverticula ACP in stations 6.1 and 4.1 and proximal kidney tubular ACP deficiency in station 4.1; (3) no ALKP differences among stations; (4) increased distal kidney tubular GGT at station 12.5 and decreased distal kidney tubular GGT at station 4.1; (5) decreased digestive diverticula G6PDH G6PDH in all stations except 12.5 and decreased proximal kidney tubular G6PDH in stations 8.1 and 6.1. It is possible that other anthropogenic and natural stressors may have affected the results in this study. However, the prevalence and increased severity of lesions in clams with highest metal body burden suggests a contaminant- associated etiology. Enzymatic and histopathologic biomarker alterations identified in this study were positively correlated with the metal body burden. Clams with the higher prevalence of diseases and enzyme alterations also showed a lower condition index and glycogen content in the month when histopathological assessment was performed. Further study will seek to develop enzymatic and histopathologic biomarkers for use in controlled laboratory conditions to help validate the field study.

Interactive toxicity of inorganic mercury and trichloroethylene in rat and human proximal tubules: Effects on apoptosis, necrosis, and glutathione status

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lash, Lawrence H.; Putt, David A.; Hueni, Sarah E.

Simultaneous or prior exposure to one chemical may alter the concurrent or subsequent response to another chemical, often in unexpected ways. This is particularly true when the two chemicals share common mechanisms of action. The present study uses the paradigm of prior exposure to study the interactive toxicity between inorganic mercury (Hg{sup 2+}) and trichloroethylene (TRI) or its metabolite S-(1,2-dichlorovinyl)-L-cysteine (DCVC) in rat and human proximal tubule. Pretreatment of rats with a subtoxic dose of Hg{sup 2+} increased expression of glutathione S-transferase-{alpha}1 (GST{alpha}1) but decreased expression of GST{alpha}2, increased activities of several GSH-dependent enzymes, and increased GSH conjugation of TRI.more » Primary cultures of rat proximal tubular (rPT) cells exhibited both necrosis and apoptosis after incubation with Hg{sup 2+}. Pretreatment of human proximal tubular (hPT) cells with Hg{sup 2+} caused little or no changes in GST expression or activities of GSH-dependent enzymes, decreased apoptosis induced by TRI or DCVC, but increased necrosis induced by DCVC. In contrast, pretreatment of hPT cells with TRI or DCVC protected from Hg{sup 2+} by decreasing necrosis and increasing apoptosis. Thus, whereas pretreatment of hPT cells with Hg{sup 2+} exacerbated cellular injury due to TRI or DCVC by shifting the response from apoptosis to necrosis, pretreatment of hPT cells with either TRI or DCVC protected from Hg{sup 2+}-induced cytotoxicity by shifting the response from necrosis to apoptosis. These results demonstrate that by altering processes related to GSH status, susceptibilities of rPT and hPT cells to acute injury from Hg{sup 2+}, TRI, or DCVC are markedly altered by prior exposures.« less

Two-dimensional transthoracic echocardiographic normal reference ranges for proximal aorta dimensions: results from the EACVI NORRE study.

PubMed

Saura, Daniel; Dulgheru, Raluca; Caballero, Luis; Bernard, Anne; Kou, Seisyou; Gonjilashvili, Natalia; Athanassopoulos, George D; Barone, Daniele; Baroni, Monica; Cardim, Nuno; Hagendorff, Andreas; Hristova, Krasimira; Lopez, Teresa; de la Morena, Gonzalo; Popescu, Bogdan A; Penicka, Martin; Ozyigit, Tolga; Rodrigo Carbonero, Jose David; Van De Veire, Nico; Von Bardeleben, Ralph Stephan; Vinereanu, Dragos; Zamorano, Jose Luis; Gori, Ann-Stephan; Cosyns, Bernard; Donal, Erwan; Habib, Gilbert; Addetia, Karima; Lang, Roberto M; Badano, Luigi P; Lancellotti, Patrizio

2017-02-01

To report normal reference ranges for echocardiographic dimensions of the proximal aorta obtained in a large group of healthy volunteers recruited using state-of-the-art cardiac ultrasound equipment, considering different measurement conventions, and taking into account gender, age, and body size of individuals. A total of 704 (mean age: 46.0 ± 13.5 years) healthy volunteers (310 men and 394 women) were prospectively recruited from the collaborating institutions of the Normal Reference Ranges for Echocardiography (NORRE) study. A comprehensive echocardiographic examination was obtained in all subjects following pre-defined protocols. Aortic dimensions were obtained in systole and diastole, following both the leading-edge to leading-edge and the inner-edge to inner-edge conventions. Diameters were measured at four levels: ventricular-arterial junction, sinuses of Valsalva, sino-tubular junction, and proximal tubular ascending aorta. Measures of aortic root in the short-axis view following the orientation of each of the three sinuses were also performed. Men had significantly larger body sizes when compared with women, and showed larger aortic dimensions independently of the measurement method used. Dimensions indexed by height and body surface area are provided, and stratification by age ranges is also displayed. In multivariable analysis, the independent predictors of aortic dimensions were age, gender, and height or body surface area. The NORRE study provides normal values of proximal aorta dimensions as assessed by echocardiography. Reference ranges for different anatomical levels using different (i) measurement conventions and (ii) at different times of the cardiac cycle (i.e. mid-systole and end-diastole) are provided. Age, gender, and body size were significant determinants of aortic dimensions. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.

Atgl gene deletion predisposes to proximal tubule damage by impairing the fatty acid metabolism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Wen; Zhang, Qiong; Cheng, Shiwu

Fibrosis is the final common pathway of chronic kidney disease (CKD). Normal lipid metabolism is integral to renal physiology, and disturbances of renal lipid metabolism are increasingly being linked with CKD, including the fibrosis. Adipose triglyceride lipase (ATGL) is the rate-limiting enzyme of lipolysis. In the present study, we used Atgl{sup −/−} mice to investigate whether ATGL played a role in the regulation of proximal convoluted tubule (PCT) lipid metabolism and renal fibrosis development. ATGL deficiency led to lipid vacuolation of PCT and tubulointerstitial fibrosis, accompanied by massive albuminuria and decreased creatinine clearance rate (Ccr). In vitro experiments indicated that inhibitionmore » of ATGL in proximal tubular cell line HK-2 promoted intracellular lipid deposition, reactive oxygen species (ROS) accumulation and cell apoptosis. Both in vitro and in vivo experiments showed that ATGL inhibition decreased the renal peroxisome proliferator-activated receptorα(PPARα) expression, which implied the suppressed lipid metabolism. The antioxidant N-acetylcysteine (NAC) could partially reverse the effect of ROS accumulation and cell apoptosis, but could not restore the PPARαdecrease. These data raise the possibility that ATGL deficiency could impair the renal fatty acid metabolism though inhibiting PPARαexpression, which may lead to lipid deposition and cell apoptosis of PCT, and finally contribute to the renal fibrosis and dysfunction. - Highlights: • Atgl{sup −/−} mice develop tubulointerstitial damage and renal dysfunction. • ATGL deficiency results in lipid accumulation and apoptosis of proximal tubular cells. • ROS scavenger alleviates the ATGL-knockdown mediated lipid accumulation and apoptosis. • PPARαdown-regulation is the reason of ROS elevating in ATGL-knockdown HK-2 cells.« less

Interobserver agreement for post mortem renal histopathology and diagnosis of acute tubular necrosis in critically ill patients.

PubMed

Glassford, Neil J; Skene, Alison; Guardiola, Maria B; Chan, Matthew J; Bagshaw, Sean M; Bellomo, Rinaldo; Solez, Kim

2017-12-01

The renal histopathology of critically ill patients dying with acute kidney injury (AKI) in intensive care units of high income countries remains uncertain. Retrospective observational assessment of interobserver agreement in the reporting of renal post mortem histopathology, and the ability of pathologists blinded to the clinical context to independently identify the presence of pre-mortem AKI from digital images of histological sections from 34 critically ill patients dying in teaching hospitals in Australia and Canada. We identified a heterogeneous cohort with a median age of 65 years (interquartile range [IQR], 56.5-77), APACHE II score of 27 (IQR, 19-33), and sepsis as the most common admission diagnosis (12/34; 35%). The most common proximate causes of death were cardiovascular (19/34; 56%) and respiratory (7/34; 21%) failure. AKI was common, with 23 patients (68%) developing RIFLE-F AKI, and 21 patients (62%) receiving renal replacement therapy. Structured reporting for tubular inflammation showed excellent agreement (kappa = 1), but no other subdomain demonstrated better than moderate agreement (kappa < 0.6). Only fair agreement (55.9% of cases; kappa = 0.23) was demonstrated on the diagnosis of moderate to severe acute tubular necrosis (ATN). Pathologist A predicted RIFLE-I or worse AKI with the diagnosis of ATN, with an overall accuracy of 61.8%; pathologist B predicted AKI with an accuracy of 35.3%. Post mortem assessment of the renal histopathology in critically ill patients is neither robust nor reproducible; independent pathologists agree poorly on the diagnosis of ATN, and their structural assessment appears dissociated from ante-mortem renal function.

Bmi-1 plays a critical role in protection from renal tubulointerstitial injury by maintaining redox balance

PubMed Central

Jin, Jianliang; Lv, Xianhui; Chen, Lulu; Zhang, Wei; Li, Jinbo; Wang, Qian; Wang, Rong; Lu, Xiang; Miao, Dengshun

2014-01-01

To determine whether Bmi-1 deficiency could lead to renal tubulointerstitial injury by mitochondrial dysfunction and increased oxidative stress in the kidney, 3-week-old Bmi-1-/- mice were treated with the antioxidant N-acetylcysteine (NAC, 1 mg mL−1) in their drinking water, or pyrro-quinoline quinone (PQQ, 4 mg kg−1 diet) in their diet for 2 weeks, and their renal phenotypes were compared with vehicle-treated Bmi1-/- and wild-type mice. Bmi-1 was knocked down in human renal proximal tubular epithelial (HK2) cells which were treated with 1 mm NAC for 72 or 96 h, and their phenotypes were compared with control cells. Five-week-old vehicle-treated Bmi-1-/- mice displayed renal interstitial fibrosis, tubular atrophy, and severe renal function impairment with decreased renal cell proliferation, increased renal cell apoptosis and senescence, and inflammatory cell infiltration. Impaired mitochondrial structure, decreased mitochondrial numbers, and increased oxidative stress occurred in Bmi-1-/- mice; subsequently, this caused DNA damage, the activation of TGF-β1/Smad signaling, and the imbalance between extracellular matrix synthesis and degradation. Oxidative stress-induced epithelial-to-mesenchymal transition of renal tubular epithelial cells was enhanced in Bmi-1 knocked down HK2 cells. All phenotypic alterations caused by Bmi-1 deficiency were ameliorated by antioxidant treatment. These findings indicate that Bmi-1 plays a critical role in protection from renal tubulointerstitial injury by maintaining redox balance and will be a novel therapeutic target for preventing renal tubulointerstitial injury. PMID:24915841

α-Ketoglutarate regulates acid-base balance through an intrarenal paracrine mechanism

PubMed Central

Tokonami, Natsuko; Morla, Luciana; Centeno, Gabriel; Mordasini, David; Ramakrishnan, Suresh Krishna; Nikolaeva, Svetlana; Wagner, Carsten A.; Bonny, Olivier; Houillier, Pascal; Doucet, Alain; Firsov, Dmitri

2013-01-01

Paracrine communication between different parts of the renal tubule is increasingly recognized as an important determinant of renal function. Previous studies have shown that changes in dietary acid-base load can reverse the direction of apical α-ketoglutarate (αKG) transport in the proximal tubule and Henle’s loop from reabsorption (acid load) to secretion (base load). Here we show that the resulting changes in the luminal concentrations of αKG are sensed by the αKG receptor OXGR1 expressed in the type B and non-A–non-B intercalated cells of the connecting tubule (CNT) and the cortical collecting duct (CCD). The addition of 1 mM αKG to the tubular lumen strongly stimulated Cl–-dependent HCO3– secretion and electroneutral transepithelial NaCl reabsorption in microperfused CCDs of wild-type mice but not Oxgr1–/– mice. Analysis of alkali-loaded mice revealed a significantly reduced ability of Oxgr1–/– mice to maintain acid-base balance. Collectively, these results demonstrate that OXGR1 is involved in the adaptive regulation of HCO3– secretion and NaCl reabsorption in the CNT/CCD under acid-base stress and establish αKG as a paracrine mediator involved in the functional coordination of the proximal and the distal parts of the renal tubule. PMID:23934124

Low Risk of Proximal Tubular Dysfunction Associated With Emtricitabine-Tenofovir Disoproxil Fumarate Preexposure Prophylaxis in Men and Women

PubMed Central

Mugwanya, Kenneth; Baeten, Jared; Celum, Connie; Donnell, Deborah; Nickolas, Thomas; Mugo, Nelly; Branch, Andrea; Tappero, Jordan; Kiarie, James; Ronald, Allan; Yin, Michael; Wyatt, Christina

2016-01-01

Objective. Tenofovir disoproxil fumarate (TDF) is associated with proximal tubular dysfunction (tubulopathy) when used in the treatment of human immunodeficiency virus (HIV) infection. We evaluated whether TDF causes tubulopathy when used as HIV preexposure prophylaxis (PrEP) and whether tubulopathy predicts clinically relevant decline (≥25%) in the estimated glomerular filtration rate (eGFR). Methods. A subgroup analysis of the Partners PrEP Study, a randomized, placebo-controlled trial of daily oral TDF, alone or with emtricitabine (FTC), in HIV-uninfected African men and women (Clinicaltrials.gov NCT00557245). Tubulopathy was assessed in concurrently obtained urine and serum samples at the 24-month or last on-treatment visit, predefined as ≥2 of the following: tubular proteinuria, euglycemic glycosuria, increased urinary phosphate, and uric acid excretion. Results. Of 1549 persons studied (776 receiving FTC-TDF, 773 receiving placebo), 64% were male, and the median age was 37 years. Over a median 24 months of study-drug exposure, the frequency of tubulopathy was 1.7% for FTC-TDF versus 1.3% for placebo (odds ratio, 1.30; 95% confidence interval, .52–3.33; P = .68); Tubulopathy occurred in 2 of 52 persons (3.8%) with versus 3 of 208 (1.4%) without ≥25% eGFR decline (adjusted odds ratio, 1.39; .10–14.0; P > .99). Conclusions. Daily oral FTC-TDF PrEP was not significantly associated with tubulopathy over the course of 24 months, nor did tubulopathy predict clinically relevant eGFR decline. PMID:27029778

Lysophosphatidic acid signaling through its receptor initiates profibrotic epithelial cell fibroblast communication mediated by epithelial cell derived connective tissue growth factor.

PubMed

Sakai, Norihiko; Chun, Jerold; Duffield, Jeremy S; Lagares, David; Wada, Takashi; Luster, Andrew D; Tager, Andrew M

2017-03-01

The expansion of the fibroblast pool is a critical step in organ fibrosis, but the mechanisms driving expansion remain to be fully clarified. We previously showed that lysophosphatidic acid (LPA) signaling through its receptor LPA 1 expressed on fibroblasts directly induces the recruitment of these cells. Here we tested whether LPA-LPA 1 signaling drives fibroblast proliferation and activation during the development of renal fibrosis. LPA 1 -deficient (LPA 1 -/- ) or -sufficient (LPA 1 +/+ ) mice were crossed to mice with green fluorescent protein expression (GFP) driven by the type I procollagen promoter (Col-GFP) to identify fibroblasts. Unilateral ureteral obstruction-induced increases in renal collagen were significantly, though not completely, attenuated in LPA 1 -/- Col-GFP mice, as were the accumulations of both fibroblasts and myofibroblasts. Connective tissue growth factor was detected mainly in tubular epithelial cells, and its levels were suppressed in LPA 1 -/- Col-GFP mice. LPA-LPA 1 signaling directly induced connective tissue growth factor expression in primary proximal tubular epithelial cells, through a myocardin-related transcription factor-serum response factor pathway. Proximal tubular epithelial cell-derived connective tissue growth factor mediated renal fibroblast proliferation and myofibroblast differentiation. Administration of an inhibitor of myocardin-related transcription factor/serum response factor suppressed obstruction-induced renal fibrosis. Thus, targeting LPA-LPA 1 signaling and/or myocardin-related transcription factor/serum response factor-induced transcription could be promising therapeutic strategies for renal fibrosis. Copyright © 2016 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

The Fate of Nephrons in Congenital Obstructive Nephropathy: Adult Recovery is Limited by Nephron Number Despite Early Release of Obstruction

PubMed Central

Sergio, Maria; Galarreta, Carolina I.; Thornhill, Barbara A.; Forbes, Michael S.; Chevalier, Robert L.

2015-01-01

Purpose Urinary tract obstruction and reduced nephron number often occur together as a result of maldevelopment of kidneys and urinary tract. We wished to determine the role of nephron number on the adaptation of remaining nephrons of mice subjected to neonatal partial unilateral ureteral obstruction (UUO) and followed through adulthood. Materials and Methods Wild-type (WT) and Os/+ mice (with 50% fewer nephrons) were subjected to sham operation or partial UUO in the first 2 days of life. Additional mice underwent release of UUO at 7 days. All kidneys were harvested at 3 weeks (weaning) or 6 weeks (adulthood). Glomerular number and area, glomerulotubular junction integrity, proximal tubular volume fraction, and interstitial fibrosis were measured by histomorphometry. Results In the obstructed kidney, UUO caused additional nephron loss in Os/+ but not WT mice. Glomerular growth from 3 to 6 weeks was impaired by ipsilateral UUO and was not preserved by release in WT or Os/+. Proximal tubular growth was impaired and interstitial collagen was increased by ipsilateral UUO in all mice. These were attenuated by release of UUO in WT mice, but were not restored in Os/+ mice. UUO increased interstitial collagen in the contralateral kidney; release of UUO enhanced tubular growth and reduced interstitial collagen. Conclusions We conclude that UUO in early postnatal development impairs adaptation to reduced nephron number and induces additional nephron loss despite release of obstruction. Premature and low birth weight infants with congenital obstructive nephropathy are likely at increased risk for progression of chronic kidney disease. PMID:25912494

Long-term treatment with tenofovir in Asian-American chronic hepatitis B patients is associated with abnormal renal phosphate handling.

PubMed

Tien, Connie; Xu, Jason J; Chan, Linda S; Chang, Mimi; Lim, Carolina; Lee, Sue; Huh, Brian; Shinada, Shuntaro; Bae, Ho S; Fong, Tse-Ling

2015-02-01

Increased risk of defective urinary phosphate reabsorption and osteoporosis has been reported in HIV and chronic hepatitis B (CHB) patients treated with tenofovir disoproxil fumarate (TDF). Goals of this study were to evaluate the prevalence of renal phosphate wasting and abnormal bone mineral density in CHB patients taking TDF compared to CHB patients treated with entecavir (ETV) and untreated CHB patients. This is a cross-sectional study of 146 consecutive Asian-American CHB patients who were treatment naïve (n = 60) or treated with either TDF (n = 42) or ETV (n = 44). Proximal tubular handling of phosphate was assessed by the maximal rate of tubular reabsorption of phosphate (TmPO4) divided by glomerular filtration rate (GFR) (TmPO4/GFR). Bone mineral density (BMD) was measured using dual X-ray absorptiometry. TmPO4/GFR was similar among CHB patients treated with TDF compared to untreated patients and patients taking ETV. However, among patients treated with ≥18 months of TDF or ETV, prevalence of abnormal TmPO4/GFR was higher among patients treated with TDF compared to ETV (48.5 % (16/33) vs. 12.5 % (3/24), p = 0.005). Overall prevalence of osteoporosis in this cohort of CHB patients was 14 %, with no significant difference between the three groups. Renal phosphate handling did not correlate with osteoporosis. Chronic hepatitis B patients treated with ≥18 months of TDF experienced an increased risk of proximal tubular dysfunction. TDF did not increase the risk of osteoporosis. Longitudinal studies are needed to confirm these findings.

Exposure of cultured human proximal tubular cells to cadmium, mercury, zinc and bismuth: toxicity and metallothionein induction.

PubMed

Rodilla, V; Miles, A T; Jenner, W; Hawksworth, G M

1998-08-14

The kidney, in particular the proximal convoluted tubule, is a major target site for the toxic effects of various metals. However, little is known about the early effects of these metals after acute exposure in man. In the present study we have evaluated the toxicity of several inorganic metal compounds (CdCl2, HgCl2, ZnCl2, and Bi(NO3)3) and the induction of metallothionein by these compounds in cultured human proximal tubular (HPT) cells for up to 4 days. The results showed that bismuth was not toxic even at the highest dose (100 microM) used, while zinc, cadmium and mercury exhibited varying degrees of toxicity, zinc being the least toxic and mercury the most potent. A significant degree of interindividual variation between the different isolates used in these experiments was also observed. All metals used in the present study induced MT, as revealed by immunocytochemistry. All metals showed maximal induction between 1 and 3 days after treatment. Although a certain amount of constitutive MT was present in the cultures, the intensity of the staining varied with time in culture and between the different isolates studied. No correlation could be made between the intensity of the staining in control cultures (indicating total amount of constitutive MT) and the susceptibility of a given isolate to metal toxicity. Furthermore, no correlation could be made between metal-induced MT and the susceptibility of a given isolate to that particular metal.

Expression of Translationally Controlled Tumor Protein in Human Kidney and in Renal Cell Carcinoma.

PubMed

Ambrosio, Maria R; Rocca, Bruno J; Barone, Aurora; Onorati, Monica; Mundo, Lucia; Crivelli, Filippo; Di Nuovo, Franca; De Falco, Giulia; del Vecchio, Maria T; Tripodi, Sergio A; Tosi, Piero

2015-01-01

Translationally controlled tumor protein is a multifaceted protein involved in several physiological and biological functions. Its expression in normal kidney and in renal carcinomas, once corroborated by functional data, may add elements to elucidate renal physiology and carcinogenesis. In this study, translationally controlled tumor protein expression was evaluated by quantitative real time polymerase chain reaction and western blotting, and its localization was examined by immunohistochemistry on 84 nephrectomies for cancer. In normal kidney protein expression was found in the cytoplasm of proximal and distal tubular cells, in cells of the thick segment of the loop of Henle, and in urothelial cells of the pelvis. It was also detectable in cells of renal carcinoma with different pattern of localization (membranous and cytoplasmic) depending on tumor histotype. Our data may suggest an involvement of translationally controlled tumor protein in normal physiology and carcinogenesis. However, functional in vitro and in vivo studies are needed to verify this hypothesis.

Expression of Translationally Controlled Tumor Protein in Human Kidney and in Renal Cell Carcinoma

PubMed Central

Ambrosio, Maria R.; Rocca, Bruno J.; Barone, Aurora; Onorati, Monica; Mundo, Lucia; Crivelli, Filippo; Di Nuovo, Franca; De Falco, Giulia; del Vecchio, Maria T.; Tripodi, Sergio A.; Tosi, Piero

2015-01-01

Translationally controlled tumor protein is a multifaceted protein involved in several physiological and biological functions. Its expression in normal kidney and in renal carcinomas, once corroborated by functional data, may add elements to elucidate renal physiology and carcinogenesis. In this study, translationally controlled tumor protein expression was evaluated by quantitative real time polymerase chain reaction and western blotting, and its localization was examined by immunohistochemistry on 84 nephrectomies for cancer. In normal kidney protein expression was found in the cytoplasm of proximal and distal tubular cells, in cells of the thick segment of the loop of Henle, and in urothelial cells of the pelvis. It was also detectable in cells of renal carcinoma with different pattern of localization (membranous and cytoplasmic) depending on tumor histotype. Our data may suggest an involvement of translationally controlled tumor protein in normal physiology and carcinogenesis. However, functional in vitro and in vivo studies are needed to verify this hypothesis. PMID:26425551

BAG3 regulates ECM accumulation in renal proximal tubular cells induced by TGF-β1.

PubMed

Du, Feng; Li, Si; Wang, Tian; Zhang, Hai-Yan; Li, De-Tian; Du, Zhen-Xian; Wang, Hua-Qin; Wang, Yan-Qiu

2015-01-01

Previously we have demonstrated that Bcl-2-associated athanogene 3 (BAG3) is increased in renal fibrosis using a rat unilateral ureteral obstruction model. The current study investigated the role of BAG3 in renal fibrosis using transforming growth factor (TGF)-β1-treated human proximal tubular epithelial (HK-2) cells. An upregulation of BAG3 in vitro models was observed, which correlated with the increased synthesis of extracellular matrix (ECM) proteins and expression of tissue-type plasminogen activator inhibitor (PAI)-1. Blockade of BAG3 induction by shorting hairpin RNA suppressed the expression of ECM proteins but had no effect on PAI-1 expression induced by TGF-β1. Forced overexpression of BAG3 selectively increased collagens. TGF-β1-induced BAG3 expression in HK-2 cells was attenuated by ERK1/2 and JNK MAPK inhibitors. In addition, forced BAG3 overexpression blocked attenuation of collagens expression by ERK1/2 and JNK inhibitors. These data suggest that ERK1/2 and JNK signaling events are involved in modulating the expression of BAG3, which would ultimately contribute to renal fibrosis by enhancing the synthesis and deposition of ECM proteins.

BAG3 regulates ECM accumulation in renal proximal tubular cells induced by TGF-β1

PubMed Central

Du, Feng; Li, Si; Wang, Tian; Zhang, Hai-Yan; Li, De-Tian; Du, Zhen-Xian; Wang, Hua-Qin; Wang, Yan-Qiu

2015-01-01

Previously we have demonstrated that Bcl-2-associated athanogene 3 (BAG3) is increased in renal fibrosis using a rat unilateral ureteral obstruction model. The current study investigated the role of BAG3 in renal fibrosis using transforming growth factor (TGF)-β1-treated human proximal tubular epithelial (HK-2) cells. An upregulation of BAG3 in vitro models was observed, which correlated with the increased synthesis of extracellular matrix (ECM) proteins and expression of tissue-type plasminogen activator inhibitor (PAI)-1. Blockade of BAG3 induction by shorting hairpin RNA suppressed the expression of ECM proteins but had no effect on PAI-1 expression induced by TGF-β1. Forced overexpression of BAG3 selectively increased collagens. TGF-β1-induced BAG3 expression in HK-2 cells was attenuated by ERK1/2 and JNK MAPK inhibitors. In addition, forced BAG3 overexpression blocked attenuation of collagens expression by ERK1/2 and JNK inhibitors. These data suggest that ERK1/2 and JNK signaling events are involved in modulating the expression of BAG3, which would ultimately contribute to renal fibrosis by enhancing the synthesis and deposition of ECM proteins. PMID:26885277

Analysis of accumulation of 99mTc-octreotide and 99mTc-EDDA/HYNIC-Tyr3-octreotide in the rat kidneys.

PubMed

Kopecky, Martin; Semecky, Vladimir; Trejtnar, Frantisek; Laznicek, Milan; Laznickova, Alice; Nachtigal, Petr; Decristoforo, Clemens; Mather, Stephen J; Mäcke, Helmut R

2004-02-01

The aim of this study was to compare renal handling and distribution of (99m)Tc-octreotide and (99m)Tc-EDDA/HYNIC-Tyr(3)-octreotide (HYNIC-TOC) in rats. In kidney perfusion experiments, the renal clearance value of (99m)Tc-octreotide was three times lower than that of (99m)Tc-EDDA/HYNIC-TOC. The predominant renal excretion of (99m)Tc-EDDA/HYNIC-TOC was associated with a high and long-term renal accumulation up to 48 hrs. Microautoradiographic results indicated that (99m)Tc-EDDA/HYNIC-TOC was retained mainly in the renal medulla within the cells of the collecting ducts and in the surrounding tissue. Lower positivity was found in the proximal and distal tubular cells. We conclude that the mechanism of renal accumulation of somatostatin analogues renal accumulation is complex and that proximal tubular reabsorption is probably not the main mechanism for uptake of (99m)Tc-EDDA/HYNIC-TOC in the kidneys. The presence of the somatostatin receptors, differences in the tonicity level within kidneys and other possible mechanisms could participate in their renal accumulation.

Effects of maternal subtotal nephrectomy on the development of the fetal kidney: A morphometric study.

PubMed

Kondo, Tomohiro; Kitano-Amahori, Yoko; Nagai, Hiroaki; Mino, Masaki; Takeshita, Ai; Kusakabe, Ken Takeshi; Okada, Toshiya

2015-11-01

The present study was designed to explore if maternal subtotal (5/6) nephrectomy affects the development of fetal rat kidneys using morphometric methods and examining whether there are any apoptotic changes in the fetal kidney. To generate 5/6 nephrectomized model rats, animals underwent 2/3 left nephrectomy on gestation day (GD) 5 and total right nephrectomy on GD 12. The fetal kidneys were examined on GDs 16 and 22. A significant decrease in fetal body weight resulting from maternal 5/6 nephrectomy was observed on GD 16, and a significant decrease in fetal renal weight and fetal body weight caused by maternal nephrectomy was observed on GD 22. Maternal 5/6 nephrectomy induced a significant increase in glomerular number, proximal tubular length, and total proximal tubular volume of fetuses on GD 22. Maternal 5/6 nephrectomy resulted in an increase in the number of apoptotic cells in the metanephric mesenchyme of the kidney on GD 16, and in the collecting tubules on GD 22. These findings suggest that maternal 5/6 nephrectomy stimulates the development of the fetal kidney while suppressing fetal growth. © 2015 Japanese Teratology Society.

Smad ubiquitination regulatory factor-2 in the fibrotic kidney: regulation, target specificity, and functional implication.

PubMed

Tan, Ruoyun; He, Weichun; Lin, Xia; Kiss, Lawrence P; Liu, Youhua

2008-05-01

Smad ubiquitination regulatory factor-2 (Smurf2) is an E3 ubiqutin ligase that plays a pivotal role in regulating TGF-beta signaling via selectively targeting key components of the Smad pathway for degradation. In this study, we have investigated the regulation of Smurf2 expression, its target specificity, and the functional implication of its induction in the fibrotic kidney. Immunohistochemical staining revealed that Smurf2 was upregulated specifically in renal tubules of kidney biopsies from patients with various nephropathies. In vitro, Smurf2 mRNA and protein were induced in human proximal tubular epithelial cells (HKC-8) upon TGF-beta1 stimulation. Ectopic expression of Smurf2 was sufficient to reduce the steady-state levels of Smad2, but not Smad1, Smad3, Smad4, and Smad7, in HKC-8 cells. Interestingly, Smurf2 was also able to downregulate the Smad transcriptional corepressors Ski, SnoN, and TG-interacting factor. Inhibition of the proteasomal pathway prevented Smurf2-mediated downregulation of Smad2 and Smad corepressors. Functionally, overexpression of Smurf2 enhanced the transcription of the TGF-beta-responsive promoter and augmented TGF-beta1-mediated E-cadherin suppression, as well as fibronectin and type I collagen induction in HKC-8 cells. These results indicate that Smurf2 specifically targets both positive and negative Smad regulators for destruction in tubular epithelial cells, thereby providing a complex fine-tuning of TGF-beta signaling. It appears that dysregulation of Smurf2 could contribute to an aberrant TGF-beta/Smad signaling in the pathogenesis of kidney fibrosis.

[Mechanism of the diuretic effect of eufillin].

PubMed

Kantariia, V A; Lebedev, A A

1975-01-01

In acute experiments on rats the xanthine diuretic euphylline did not block the short-circuited current in the proximal tubule, nor did it lower the transtubular potential and the transepithelial resistance of the nephron wall. The diuretic speeded up significantly the passage of the tubular fluid along the proximal region of the nephron and Henle's loop. The dihydroergotoxin and inderal blocking of adrenoreceptors did not produce any influence on the renal effects of the xanthine agent. Reserpine totally blocked the diuretic and saluretic effects of euphylline, whereas other sympatholytics, such as alpha-methyl-dofa, anthabus and hemedin, did not modify the action of the diuretic.

Sirt1 protects against oxidative stress-induced renal tubular cell apoptosis by the bidirectional regulation of catalase expression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hasegawa, Kazuhiro; Wakino, Shu; Yoshioka, Kyoko

2008-07-18

NAD{sup +}-dependent protein deacetylase Sirt1 regulates cellular apoptosis. We examined the role of Sirt1 in renal tubular cell apoptosis by using HK-2 cells, proximal tubular cell lines with or without reactive oxygen species (ROS), H{sub 2}O{sub 2}. Without any ROS, Sirt1 inhibitors enhanced apoptosis and the expression of ROS scavenger, catalase, and Sirt1 overexpression downregulated catalase. When apoptosis was induced with H{sub 2}O{sub 2}, Sirt1 was upregulated with the concomitant increase in catalase expression. Sirt1 overexpression rescued H{sub 2}O{sub 2}-induced apoptosis through the upregulation of catalase. H{sub 2}O{sub 2} induced the nuclear accumulation of forkhead transcription factor, FoxO3a and themore » gene silencing of FoxO3a enhanced H{sub 2}O{sub 2}-induced apoptosis. In conclusion, endogenous Sirt1 maintains cell survival by regulating catalase expression and by preventing the depletion of ROS required for cell survival. In contrast, excess ROS upregulates Sirt1, which activates FoxO3a and catalase leading to rescuing apoptosis. Thus, Sirt1 constitutes a determinant of renal tubular cell apoptosis by regulating cellular ROS levels.« less

Tubular iron deposition and iron handling proteins in human healthy kidney and chronic kidney disease.

PubMed

Raaij, Sanne van; Swelm, Rachel van; Bouman, Karlijn; Cliteur, Maaike; Heuvel, Marius van den; Pertijs, Jeanne; Patel, Dominic; Bass, Paul; Goor, Harry van; Unwin, Robert; Srai, Surjit Kaila; Swinkels, Dorine

2018-06-19

Iron is suggested to play a detrimental role in the progression of chronic kidney disease (CKD). The kidney recycles iron back into the circulation. However, the localization of proteins relevant for physiological tubular iron handling and their potential role in CKD remain unclear. We examined associations between iron deposition, expression of iron handling proteins and tubular injury in kidney biopsies from CKD patients and healthy controls using immunohistochemistry. Iron was deposited in proximal (PT) and distal tubules (DT) in 33% of CKD biopsies, predominantly in pathologies with glomerular dysfunction, but absent in controls. In healthy kidney, PT contained proteins required for iron recycling including putative iron importers ZIP8, ZIP14, DMT1, iron storage proteins L- and H-ferritin and iron exporter ferroportin, while DT only contained ZIP8, ZIP14, and DMT1. In CKD, iron deposition associated with increased intensity of iron importers (ZIP14, ZIP8), storage proteins (L-, H-ferritin), and/or decreased ferroportin abundance. This demonstrates that tubular iron accumulation may result from increased iron uptake and/or inadequate iron export. Iron deposition associated with oxidative injury as indicated by heme oxygenase-1 abundance. In conclusion, iron deposition is relatively common in CKD, and may result from altered molecular iron handling and may contribute to renal injury.

Genome-Wide Association Studies of Metabolites in Patients with CKD Identify Multiple Loci and Illuminate Tubular Transport Mechanisms.

PubMed

Li, Yong; Sekula, Peggy; Wuttke, Matthias; Wahrheit, Judith; Hausknecht, Birgit; Schultheiss, Ulla T; Gronwald, Wolfram; Schlosser, Pascal; Tucci, Sara; Ekici, Arif B; Spiekerkoetter, Ute; Kronenberg, Florian; Eckardt, Kai-Uwe; Oefner, Peter J; Köttgen, Anna

2018-05-01

Background The kidneys have a central role in the generation, turnover, transport, and excretion of metabolites, and these functions can be altered in CKD. Genetic studies of metabolite concentrations can identify proteins performing these functions. Methods We conducted genome-wide association studies and aggregate rare variant tests of the concentrations of 139 serum metabolites and 41 urine metabolites, as well as their pairwise ratios and fractional excretions in up to 1168 patients with CKD. Results After correction for multiple testing, genome-wide significant associations were detected for 25 serum metabolites, two urine metabolites, and 259 serum and 14 urinary metabolite ratios. These included associations already known from population-based studies. Additional findings included an association for the uremic toxin putrescine and variants upstream of an enzyme catalyzing the oxidative deamination of polyamines ( AOC1 , P -min=2.4×10 -12 ), a relatively high carrier frequency (2%) for rare deleterious missense variants in ACADM that are collectively associated with serum ratios of medium-chain acylcarnitines ( P -burden=6.6×10 -16 ), and associations of a common variant in SLC7A9 with several ratios of lysine to neutral amino acids in urine, including the lysine/glutamine ratio ( P =2.2×10 -23 ). The associations of this SLC7A9 variant with ratios of lysine to specific neutral amino acids were much stronger than the association with lysine concentration alone. This finding is consistent with SLC7A9 functioning as an exchanger of urinary cationic amino acids against specific intracellular neutral amino acids at the apical membrane of proximal tubular cells. Conclusions Metabolomic indices of specific kidney functions in genetic studies may provide insight into human renal physiology. Copyright © 2018 by the American Society of Nephrology.

Dysfunctional tubular endoplasmic reticulum constitutes a pathological feature of Alzheimer's disease.

PubMed

Sharoar, M G; Shi, Q; Ge, Y; He, W; Hu, X; Perry, G; Zhu, X; Yan, R

2016-09-01

Pathological features in Alzheimer's brains include mitochondrial dysfunction and dystrophic neurites (DNs) in areas surrounding amyloid plaques. Using a mouse model that overexpresses reticulon 3 (RTN3) and spontaneously develops age-dependent hippocampal DNs, here we report that DNs contain both RTN3 and REEPs, topologically similar proteins that can shape tubular endoplasmic reticulum (ER). Importantly, ultrastructural examinations of such DNs revealed gradual accumulation of tubular ER in axonal termini, and such abnormal tubular ER inclusion is found in areas surrounding amyloid plaques in biopsy samples from Alzheimer's disease (AD) brains. Functionally, abnormally clustered tubular ER induces enhanced mitochondrial fission in the early stages of DN formation and eventual mitochondrial degeneration at later stages. Furthermore, such DNs are abrogated when RTN3 is ablated in aging and AD mouse models. Hence, abnormally clustered tubular ER can be pathogenic in brain regions: disrupting mitochondrial integrity, inducing DNs formation and impairing cognitive function in AD and aging brains.

Mechanism of intracellular signal transduction during injury of renal tubular cells induced by postasphyxial serum in neonates with asphyxia.

PubMed

Zhao, Jin; Dong, Wen-Bin; Li, Peng-yun; Deng, Chun-liang

2009-01-01

Renal injury is a severe and extremely common complication that occurs early in neonates with asphyxia. Reperfusion injury has been suggested as the cause of kidney damage during resuscitation of neonatal asphyxia. Previous studies have demonstrated that postasphyxial serum from neonates with asphyxia may result in apoptosis of renal tubular cells. However, the mechanisms that mediate renal tubular cell apoptosis induced by postasphyxial serum remain poorly understood. In this report we investigate the intracellular signal transduction mechanisms that operate during injury of renal tubular cells induced by postasphyxial serum in neonates. Cultured human renal proximal tubular cells HK-2 cell were exposed to 10% fetal calf serum (normal control), 20% postasphyxial serum or 20% postasphyxial serum with pyrrolidine dithiocarbamate (PDTC). The expression of both BAD and BAX in the cytoplasm was detected by immunohistochemistry. The mitochondria membrane potential (Deltapsim) was examined by confocal microscopy, and the release of the apoptogenic mitochondrial proteins cytochrome C and AIF was assessed by Western blot analysis. Loss of mitochondria membrane potential was detected in HK-2 cells treated with 20% postasphyxial serum as compared to cells in normal serum or PTDC-pretreated cells in 20% postasphyxial serum. A significant increase of Bad and Bax protein expression was also detected, along with the release of cytochrome C and AIF from mitochondria to cytosol in the postasphyxial serum treated cells, but not in the normal or PTDC-pretreated control cells. Our findings suggest that postasphyxial serum may induce renal tubular cell apoptosis through the mitochondrial pathway, and its intracellular signal transduction mechanism includes the activation of nuclear factor-kappaB. Copyright 2009 S. Karger AG, Basel.

Loxosceles gaucho Venom-Induced Acute Kidney Injury – In Vivo and In Vitro Studies

PubMed Central

Lucato, Rui V.; Abdulkader, Regina C. R. M.; Barbaro, Katia C.; Mendes, Glória E.; Castro, Isac; Baptista, Maria A. S. F.; Cury, Patrícia M.; Malheiros, Denise M. C.; Schor, Nestor; Yu, Luis; Burdmann, Emmanuel A.

2011-01-01

Background Accidents caused by Loxosceles spider may cause severe systemic reactions, including acute kidney injury (AKI). There are few experimental studies assessing Loxosceles venom effects on kidney function in vivo. Methodology/Principal Findings In order to test Loxosceles gaucho venom (LV) nephrotoxicity and to assess some of the possible mechanisms of renal injury, rats were studied up to 60 minutes after LV 0.24 mg/kg or saline IV injection (control). LV caused a sharp and significant drop in glomerular filtration rate, renal blood flow and urinary output and increased renal vascular resistance, without changing blood pressure. Venom infusion increased significantly serum creatine kinase and aspartate aminotransferase. In the LV group renal histology analysis found acute epithelial tubular cells degenerative changes, presence of cell debris and detached epithelial cells in tubular lumen without glomerular or vascular changes. Immunohistochemistry disclosed renal deposition of myoglobin and hemoglobin. LV did not cause injury to a suspension of fresh proximal tubules isolated from rats. Conclusions/Significance Loxosceles gaucho venom injection caused early AKI, which occurred without blood pressure variation. Changes in glomerular function occurred likely due to renal vasoconstriction and rhabdomyolysis. Direct nephrotoxicity could not be demonstrated in vitro. The development of a consistent model of Loxosceles venom-induced AKI and a better understanding of the mechanisms involved in the renal injury may allow more efficient ways to prevent or attenuate the systemic injury after Loxosceles bite. PMID:21655312

Dissociation between the effects of P1, P4-diadenosine tetraphosphate (Ap4A) on renal haemodynamics and tubular function in anaesthetized rats.

PubMed

Jankowski, M; Angielski, S; Szczepańska-Konkel, M

2008-03-01

Previous studies from our laboratory have reported a marked reduction in glomerular filtration rate (GFR) and sodium reabsorption in renal proximal tubule during intravenous infusion of P(1),P(4)-diadenosine tetraphosphate (Ap(4)A) at dose of 1.0 micromol/kg + 10 nmol/kg/min (i.v., injection followed by infusion) in anaesthetized Wistar rats. In the present study, the changes of GFR and urine sodium excretion were investigated in response to systemic infusion of Ap(4)A at different doses. Ap(4)A at dose of 0.1 micromol/kg + 1.0 nmol/kg/min did not change GFR and sodium urinary excretion whereas 2-fold higher dose produced significant (3.4-fold) increase in sodium excretion without changes in GFR. Significant but transient reduction in GFR by approximately 21% was observed during infusion of Ap(4)A at dose of 0.5 micromol/kg + 5.0 nmol/kg/min. Higher doses of Ap(4)A (1.0 micromol/kg + 10 nmol/kg/min and 2.0 micromol/kg + 20 nmol/kg/min) reduction in GFR and marked natriuresis. Our results suggest that tubular sodium transport systems are more sensitive to Ap(4)A than systems involved in GFR regulation.

Potential immunotoxic effects of trichloroethylene-induced IV allergic reaction in renal impairment

PubMed Central

Yu, Jun-Feng; Feng, Yan-Yan

2017-01-01

Trichloroethylene (TCE) is known to induce allergic contact dermatitis and subsequent occupational medicamentosa-like dermatitis (OMLD) with multi-system injuries, including liver, kidney, and skin injuries. However, the mechanisms underlying immune system dysfunction that result in organ injury have not yet been clearly elucidated. In the present study, we measured the levels of secreted cytokines by effect or T cells in TCE-treated guinea pigs to better understand the contribution of allergic disorders in renal injuries. We immunized guinea pigs with trichloroethylene using the Guinea Pig Maximization Test (GPMT) and scored the inflammation on the guinea pigs’ skin. The kidney function and ultra-structural changes in the kidneys were detected using biochemical methods and electron microscopy. The deposition of cytokines was determined using immunohistochemistry. The sensitization rate was 63.16% in the TCE-sensitized groups. The electron microscopy results showed tubular epithelial cell mitochondrial swelling, vacuolar degeneration, and atrophy of the microvillus in the sensitized groups. A high degree of cytokine deposition was observed in the renal tubular proximal epithelial cells in the TCE-sensitized groups. As observed in this study, the variation in the level of immune system activation not only indicates that TCE can largely magnify the immune reaction but also suggests a potential role of immune dysfunction in renal impairment. PMID:28867961

Renal albumin absorption in physiology and pathology.

PubMed

Birn, H; Christensen, E I

2006-02-01

Albumin is the most abundant plasmaprotein serving multiple functions as a carrier of metabolites, hormones, vitamins, and drugs, as an acid/base buffer, as antioxidant and by supporting the oncotic pressure and volume of the blood. The presence of albumin in urine is considered to be the result of the balance between glomerular filtration and tubular reabsorption. Albuminuria has been accepted as an independent risk factor and a marker for renal as well as cardiovascular disease, and during the past decade, evidence has suggested that albumin itself may cause progression of renal disease. Thus, the reduction of proteinuria and, in particular, albuminuria has become a target in itself to prevent deterioration of renal function. Studies have shown albumin and its ligands to induce expression of inflammatory and fibrogenic mediators, and it has been hypothesized that increased filtration of albumin causes excessive tubular reabsorption, resulting in inflammation and fibrosis, resulting in the loss of renal function. In addition, it is known that tubular dysfunction in itself may cause albuminuria owing to decreased reabsorption of filtered albumin, and, recently, it has been suggested that significant amounts of albumin fragments are excreted in the urine as a result of tubular degradation. Thus, although both tubular and glomerular dysfunction influences renal handling of albumin, it appears that tubular reabsorption plays a central role in mediating the effects of albumin on renal function. The present paper will review the mechanisms for tubular albumin uptake and the possible implications for the development of renal disease.

Advanced Glycated End-Products Affect HIF-Transcriptional Activity in Renal Cells

PubMed Central

Bondeva, Tzvetanka; Heinzig, Juliane; Ruhe, Carola

2013-01-01

Advanced glycated end-products (AGEs) are ligands of the receptor for AGEs and increase in diabetic disease. MAPK organizer 1 (Morg1) via its binding partner prolyl-hydroxylase domain (PHD)-3 presumably plays a role in the regulation of hypoxia-inducible factor (HIF)-1α and HIF-2α transcriptional activation. The purpose of this study was to analyze the influence of AGEs on Morg1 expression and its correlation to PHD3 activity and HIF-transcriptional activity in various renal cell types. The addition of glycated BSA (AGE-BSA) significantly up-regulated Morg1 mRNA levels in murine mesangial cells and down-regulated it in murine proximal tubular cells and differentiated podocytes. These effects were reversible when the cells were preincubated with a receptor for α-AGE antibody. AGE-BSA treatment induced a relocalization of the Morg1 cellular distribution compared with nonglycated control-BSA. Analysis of PHD3 activity demonstrated an elevated PHD3 enzymatic activity in murine mesangial cells but an inhibition in murine proximal tubular cells and podocytes after the addition of AGE-BSA. HIF-transcriptional activity was also affected by AGE-BSA treatment. Reporter gene assays and EMSAs showed that AGEs regulate HIF- transcriptional activity under nonhypoxic conditions in a cell type-specific manner. In proximal tubular cells, AGE-BSA stimulation elevated mainly HIF-1α transcriptional activity and to a lesser extent HIF-2α. We also detected an increased expression of the HIF-1α and the HIF-2α proteins in kidneys from Morg1 heterozygous (HZ) placebo mice compared with the Morg1 wild-type (WT) placebo-treated mice, and the HIF-1α protein expression in the Morg1 HZ streptozotocin-treated mice was significantly higher than the WT streptozotocin-treated mice. Analysis of isolated mesangial cells from Morg1 HZ (±) and WT mice showed an inhibited PHD3 activity and an increased HIF-transcriptional activity in cells with only one Morg1 allele. These findings are important for a better understanding of the molecular mechanisms of diabetic nephropathy. PMID:24030251

A Bioinformatics Approach Identifies Signal Transducer and Activator of Transcription-3 and Checkpoint Kinase 1 as Upstream Regulators of Kidney Injury Molecule-1 after Kidney Injury

PubMed Central

Ajay, Amrendra Kumar; Kim, Tae-Min; Ramirez-Gonzalez, Victoria; Park, Peter J.; Frank, David A.

2014-01-01

Kidney injury molecule-1 (KIM-1)/T cell Ig and mucin domain-containing protein-1 (TIM-1) is upregulated more than other proteins after AKI, and it is highly expressed in renal damage of various etiologies. In this capacity, KIM-1/TIM-1 acts as a phosphatidylserine receptor on the surface of injured proximal tubular epithelial cells, mediating phagocytosis of apoptotic cells, and it may also act as a costimulatory molecule for immune cells. Despite recognition of KIM-1 as an important therapeutic target for kidney disease, the regulators of KIM-1 transcription in the kidney remain unknown. Using a bioinformatics approach, we identified upstream regulators of KIM-1 after AKI. In response to tubular injury in rat and human kidneys or oxidant stress in human proximal tubular epithelial cells (HPTECs), KIM-1 expression increased significantly in a manner that corresponded temporally and regionally with increased phosphorylation of checkpoint kinase 1 (Chk1) and STAT3. Both ischemic and oxidant stress resulted in a dramatic increase in reactive oxygen species that phosphorylated and activated Chk1, which subsequently bound to STAT3, phosphorylating it at S727. Furthermore, STAT3 bound to the KIM-1 promoter after ischemic and oxidant stress, and pharmacological or genetic induction of STAT3 in HPTECs increased KIM-1 mRNA and protein levels. Conversely, inhibition of STAT3 using siRNAs or dominant negative mutants reduced KIM-1 expression in a kidney cancer cell line (769-P) that expresses high basal levels of KIM-1. These observations highlight Chk1 and STAT3 as critical upstream regulators of KIM-1 expression after AKI and may suggest novel approaches for therapeutic intervention. PMID:24158981

Low Risk of Proximal Tubular Dysfunction Associated With Emtricitabine-Tenofovir Disoproxil Fumarate Preexposure Prophylaxis in Men and Women.

PubMed

Mugwanya, Kenneth; Baeten, Jared; Celum, Connie; Donnell, Deborah; Nickolas, Thomas; Mugo, Nelly; Branch, Andrea; Tappero, Jordan; Kiarie, James; Ronald, Allan; Yin, Michael; Wyatt, Christina

2016-10-01

Tenofovir disoproxil fumarate (TDF) is associated with proximal tubular dysfunction (tubulopathy) when used in the treatment of human immunodeficiency virus (HIV) infection. We evaluated whether TDF causes tubulopathy when used as HIV preexposure prophylaxis (PrEP) and whether tubulopathy predicts clinically relevant decline (≥25%) in the estimated glomerular filtration rate (eGFR). A subgroup analysis of the Partners PrEP Study, a randomized, placebo-controlled trial of daily oral TDF, alone or with emtricitabine (FTC), in HIV-uninfected African men and women (Clinicaltrials.gov NCT00557245). Tubulopathy was assessed in concurrently obtained urine and serum samples at the 24-month or last on-treatment visit, predefined as ≥2 of the following: tubular proteinuria, euglycemic glycosuria, increased urinary phosphate, and uric acid excretion. Of 1549 persons studied (776 receiving FTC-TDF, 773 receiving placebo), 64% were male, and the median age was 37 years. Over a median 24 months of study-drug exposure, the frequency of tubulopathy was 1.7% for FTC-TDF versus 1.3% for placebo (odds ratio, 1.30; 95% confidence interval, .52-3.33; P = .68); Tubulopathy occurred in 2 of 52 persons (3.8%) with versus 3 of 208 (1.4%) without ≥25% eGFR decline (adjusted odds ratio, 1.39; .10-14.0; P > .99). Daily oral FTC-TDF PrEP was not significantly associated with tubulopathy over the course of 24 months, nor did tubulopathy predict clinically relevant eGFR decline. © The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail journals.permissions@oup.com.

The role of oxidative stress in the ochratoxin A-mediated toxicity in proximal tubular cells.

PubMed

Schaaf, G J; Nijmeijer, S M; Maas, R F M; Roestenberg, P; de Groene, E M; Fink-Gremmels, J

2002-11-20

Balkan endemic nephropathy (BEN), a disease characterized by progressive renal fibrosis in human patients, has been associated with exposure to ochratoxin A (OTA). This mycotoxin is a frequent contaminant of human and animal food products, and is toxic to all animal species tested. OTA predominantly affects the kidney and is known to accumulate in the proximal tubule (PT). The induction of oxidative stress is implicated in the toxicity of this mycotoxin. In the present study, primary rat PT cells and LLC-PK(1) cells, which express characteristics of the PT, were used to investigate the OTA-mediated oxidative stress response. OTA exposure of these cells resulted in a concentration-dependent elevation of reactive oxygen species (ROS) levels, depletion of cellular glutathione (GSH) levels and an increase in the formation of 8-oxoguanine. The OTA-induced ROS response was significantly reduced following treatment with alpha-tocopherol (TOCO). However, this chain-braking anti-oxidant did not reduce the cytotoxicity of OTA and was unable to prevent the depletion of total GSH levels in OTA-exposed cells. In contrast, pre-incubation of the cell with N-acetyl-L-cysteine (NAC) completely prevented the OTA-induced increase in ROS levels as well as the formation of 8-oxoguanine and completely protected against the cytotoxicity of OTA. In addition, NAC treatment also limited the GSH depletion in OTA-exposed PT- and LLC-PK(1) cells. From these data, we conclude that oxidative stress contributes to the tubular toxicity of OTA. Subsequently, cellular GSH levels play a pivotal role in limiting the short-term toxicity of this mycotoxin in renal tubular cells.

Laser Capture Microdissection and Multiplex-Tandem PCR Analysis of Proximal Tubular Epithelial Cell Signaling in Human Kidney Disease

PubMed Central

Wilkinson, Ray; Wang, Xiangju; Kassianos, Andrew J.; Zuryn, Steven; Roper, Kathrein E.; Osborne, Andrew; Sampangi, Sandeep; Francis, Leo; Raghunath, Vishwas; Healy, Helen

2014-01-01

Interstitial fibrosis, a histological process common to many kidney diseases, is the precursor state to end stage kidney disease, a devastating and costly outcome for the patient and the health system. Fibrosis is historically associated with chronic kidney disease (CKD) but emerging evidence is now linking many forms of acute kidney disease (AKD) with the development of CKD. Indeed, we and others have observed at least some degree of fibrosis in up to 50% of clinically defined cases of AKD. Epithelial cells of the proximal tubule (PTEC) are central in the development of kidney interstitial fibrosis. We combine the novel techniques of laser capture microdissection and multiplex-tandem PCR to identify and quantitate “real time” gene transcription profiles of purified PTEC isolated from human kidney biopsies that describe signaling pathways associated with this pathological fibrotic process. Our results: (i) confirm previous in-vitro and animal model studies; kidney injury molecule-1 is up-regulated in patients with acute tubular injury, inflammation, neutrophil infiltration and a range of chronic disease diagnoses, (ii) provide data to inform treatment; complement component 3 expression correlates with inflammation and acute tubular injury, (iii) identify potential new biomarkers; proline 4-hydroxylase transcription is down-regulated and vimentin is up-regulated across kidney diseases, (iv) describe previously unrecognized feedback mechanisms within PTEC; Smad-3 is down-regulated in many kidney diseases suggesting a possible negative feedback loop for TGF-β in the disease state, whilst tight junction protein-1 is up-regulated in many kidney diseases, suggesting feedback interactions with vimentin expression. These data demonstrate that the combined techniques of laser capture microdissection and multiplex-tandem PCR have the power to study molecular signaling within single cell populations derived from clinically sourced tissue. PMID:24475278

The Fate of Nephrons in Congenital Obstructive Nephropathy: Adult Recovery is Limited by Nephron Number Despite Early Release of Obstruction.

PubMed

Sergio, Maria; Galarreta, Carolina I; Thornhill, Barbara A; Forbes, Michael S; Chevalier, Robert L

2015-11-01

Urinary tract obstruction and reduced nephron number often occur together as a result of maldevelopment of the kidneys and the urinary tract. We determined the role of nephron number on adaptation of the remaining nephrons of mice subjected to neonatal partial unilateral ureteral obstruction followed through adulthood. Wild-type and Os/+ mice (the latter with 50% fewer nephrons) underwent sham operation or partial unilateral ureteral obstruction in the first 2 days of life. Additional mice underwent release of unilateral ureteral obstruction at 7 days. All kidneys were harvested at 3 weeks (weaning) or 6 weeks (adulthood). Glomerular number and area, glomerulotubular junction integrity, proximal tubular volume fraction and interstitial fibrosis were measured by histomorphometry. In the obstructed kidney unilateral ureteral obstruction caused additional nephron loss in Os/+ but not in wild-type mice. Glomerular growth from 3 to 6 weeks was impaired by ipsilateral obstruction and not preserved by release in wild-type or Os/+ mice. Proximal tubular growth was impaired and interstitial collagen was increased by ipsilateral obstruction in all mice. These conditions were attenuated by release of unilateral ureteral obstruction in wild-type mice but were not restored in Os/+ mice. Unilateral ureteral obstruction increased interstitial collagen in the contralateral kidney while release of obstruction enhanced tubular growth and reduced interstitial collagen. Unilateral ureteral obstruction in early postnatal development impairs adaptation to reduced nephron number and induces additional nephron loss despite release of obstruction. Premature and low birth weight infants with congenital obstructive nephropathy are likely at increased risk for progression of chronic kidney disease. Copyright © 2015 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Polycystin-1 Binds Par3/aPKC and Controls Convergent Extension During Renal Tubular Morphogenesis

PubMed Central

Castelli, Maddalena; Boca, Manila; Chiaravalli, Marco; Ramalingam, Harini; Rowe, Isaline; Distefano, Gianfranco; Carroll, Thomas; Boletta, Alessandra

2013-01-01

Several organs, including lungs and kidneys, are formed by epithelial tubes whose proper morphogenesis ensures correct function. This is best exemplified by the kidney, where defective establishment or maintanance of tubular diameter results in polycystic kidney disease, a common genetic disorder. Most polycystic kidney disease cases result from loss-of-function mutations in the PKD1 gene, encoding Polycystin-1 (PC-1), a large receptor of unknown function. Here we demonstrate that PC-1 plays an essential role in establishment of correct tubular diameter during nephron development. PC-1 associates with Par3 favoring the assembly of a pro-polarizing Par3/aPKC complex and it regulates a program of cell polarity important for oriented cell migration and for a convergent extension-like process during tubular morphogenesis. Par3 inactivation in the developing kidney results in defective convergent extension and tubular morphogenesis and in renal cyst formation. Our data define PC-1 as central to cell polarization and to epithelial tube morphogenesis and homeostasis. PMID:24153433

Polycystin-1 binds Par3/aPKC and controls convergent extension during renal tubular morphogenesis

NASA Astrophysics Data System (ADS)

Castelli, Maddalena; Boca, Manila; Chiaravalli, Marco; Ramalingam, Harini; Rowe, Isaline; Distefano, Gianfranco; Carroll, Thomas; Boletta, Alessandra

2013-10-01

Several organs, including the lungs and kidneys, are formed by epithelial tubes whose proper morphogenesis ensures correct function. This is best exemplified by the kidney, where defective establishment or maintenance of tubular diameter results in polycystic kidney disease, a common genetic disorder. Most polycystic kidney disease cases result from loss-of-function mutations in the PKD1 gene, encoding Polycystin-1, a large receptor of unknown function. Here we demonstrate that PC-1 has an essential role in the establishment of correct tubular diameter during nephron development. Polycystin-1 associates with Par3 favouring the assembly of a pro-polarizing Par3/aPKC complex and it regulates a programme of cell polarity important for oriented cell migration and for a convergent extension-like process during tubular morphogenesis. Par3 inactivation in the developing kidney results in defective convergent extension and tubular morphogenesis, and in renal cyst formation. Our data define Polycystin-1 as central to cell polarization and to epithelial tube morphogenesis and homeostasis.

N-acetyl-cysteine increases cellular dysfunction in progressive chronic kidney damage after acute kidney injury by dampening endogenous antioxidant responses.

PubMed

Small, David M; Sanchez, Washington Y; Roy, Sandrine F; Morais, Christudas; Brooks, Heddwen L; Coombes, Jeff S; Johnson, David W; Gobe, Glenda C

2018-05-01

Oxidative stress and mitochondrial dysfunction exacerbate acute kidney injury (AKI), but their role in any associated progress to chronic kidney disease (CKD) remains unclear. Antioxidant therapies often benefit AKI, but their benefits in CKD are controversial since clinical and preclinical investigations often conflict. Here we examined the influence of the antioxidant N-acetyl-cysteine (NAC) on oxidative stress and mitochondrial function during AKI (20-min bilateral renal ischemia plus reperfusion/IR) and progression to chronic kidney pathologies in mice. NAC (5% in diet) was given to mice 7 days prior and up to 21 days post-IR (21d-IR). NAC treatment resulted in the following: prevented proximal tubular epithelial cell apoptosis at early IR (40-min postischemia), yet enhanced interstitial cell proliferation at 21d-IR; increased transforming growth factor-β1 expression independent of IR time; and significantly dampened nuclear factor-like 2-initiated cytoprotective signaling at early IR. In the long term, NAC enhanced cellular metabolic impairment demonstrated by increased peroxisome proliferator activator-γ serine-112 phosphorylation at 21d-IR. Intravital multiphoton microscopy revealed increased endogenous fluorescence of nicotinamide adenine dinucleotide (NADH) in cortical tubular epithelial cells during ischemia, and at 21d-IR that was not attenuated with NAC. Fluorescence lifetime imaging microscopy demonstrated persistent metabolic impairment by increased free/bound NADH in the cortex at 21d-IR that was enhanced by NAC. Increased mitochondrial dysfunction in remnant tubular cells was demonstrated at 21d-IR by tetramethylrhodamine methyl ester fluorimetry. In summary, NAC enhanced progression to CKD following AKI not only by dampening endogenous cellular antioxidant responses at time of injury but also by enhancing persistent kidney mitochondrial and metabolic dysfunction.

HIV Infection, Tenofovir, and Urine α1-Microglobulin: A Cross-sectional Analysis in the Multicenter AIDS Cohort Study.

PubMed

Jotwani, Vasantha; Scherzer, Rebecca; Estrella, Michelle M; Jacobson, Lisa P; Witt, Mallory D; Palella, Frank J; Macatangay, Bernard; Bennett, Michael; Parikh, Chirag R; Ix, Joachim H; Shlipak, Michael G

2016-10-01

Tenofovir disoproxil fumarate (TDF) can cause proximal tubular damage and chronic kidney disease in human immunodeficiency virus (HIV)-infected individuals. Urine α1-microglobulin (A1M), a low-molecular-weight protein indicative of proximal tubular dysfunction, may enable earlier detection of TDF-associated tubular toxicity. Cross-sectional. 883 HIV-infected and 350 -uninfected men enrolled in the Multicenter AIDS Cohort Study. HIV infection and TDF exposure. Urine A1M level. Urine A1M was detectable in 737 (83%) HIV-infected and 202 (58%) -uninfected men (P<0.001). Among HIV-infected participants, 573 (65%) were current TDF users and 112 (13%) were past TDF users. After multivariable adjustment including demographics, traditional kidney disease risk factors, and estimated glomerular filtration rate, HIV infection was associated with 136% (95% CI, 104%-173%) higher urine A1M levels and 1.5-fold (95% CI, 1.3- to 1.6-fold) prevalence of detectable A1M. When participants were stratified by TDF exposure, HIV infection was associated with higher adjusted A1M levels, by 164% (95% CI, 127%-208%) among current users, 124% (95% CI, 78%-183%) among past users, and 76% (95% CI, 45%-115%) among never users. Among HIV-infected participants, each year of cumulative TDF exposure was associated with 7.6% (95% CI, 5.4%-9.9%) higher A1M levels in fully adjusted models, a 4-fold effect size relative to advancing age (1.8% [95% CI, 0.9%-2.7%] per year). Each year since TDF treatment discontinuation was associated with 4.9% (95% CI, -9.4%--0.2%) lower A1M levels among past users. Results may not be generalizable to women. HIV-infected men had higher urine A1M levels compared with HIV-uninfected men. Among HIV-infected men, cumulative TDF exposure was associated with incrementally higher A1M levels, whereas time since TDF treatment discontinuation was associated with progressively lower A1M levels. Urine A1M appears to be a promising biomarker for detecting and monitoring TDF-associated tubular toxicity. Copyright © 2016 National Kidney Foundation, Inc. All rights reserved.

Proximal tubular secretion of creatinine by organic cation transporter OCT2 in cancer patients.

PubMed

Ciarimboli, Giuliano; Lancaster, Cynthia S; Schlatter, Eberhard; Franke, Ryan M; Sprowl, Jason A; Pavenstädt, Hermann; Massmann, Vivian; Guckel, Denise; Mathijssen, Ron H J; Yang, Wenjian; Pui, Ching-Hon; Relling, Mary V; Herrmann, Edwin; Sparreboom, Alex

2012-02-15

Knowledge of transporters responsible for the renal secretion of creatinine is key to a proper interpretation of serum creatinine and/or creatinine clearance as markers of renal function in cancer patients receiving chemotherapeutic agents. Creatinine transport was studied in transfected HEK293 cells in vitro and in wild-type mice and age-matched organic cation transporter 1 and 2-deficient [Oct1/2(-/-)] mice ex vivo and in vivo. Clinical pharmacogenetic and transport inhibition studies were done in two separate cohorts of cancer patients. Compared with wild-type mice, creatinine clearance was significantly impaired in Oct1/2(-/-) mice. Furthermore, creatinine inhibited organic cation transport in freshly isolated proximal tubules from wild-type mice and humans, but not in those from Oct1/2(-/-) mice. In a genetic association analysis (n = 590), several polymorphisms around the OCT2/SLC22A2 gene locus, including rs2504954 (P = 0.000873), were significantly associated with age-adjusted creatinine levels. Furthermore, in cancer patients (n = 68), the OCT2 substrate cisplatin caused an acute elevation of serum creatinine (P = 0.0083), consistent with inhibition of an elimination pathway. Collectively, this study shows that OCT2 plays a decisive role in the renal secretion of creatinine. This process can be inhibited by OCT2 substrates, which impair the usefulness of creatinine as a marker of renal function. ©2012 AACR.

Effects of Hyperbaric Oxygen Treatment on Renal System.

PubMed

Tezcan, Orhan; Caliskan, Ahmet; Demirtas, Sinan; Yavuz, Celal; Kuyumcu, Mahir; Nergiz, Yusuf; Guzel, Abdulmenap; Karahan, Oguz; Ari, Seyhmus; Soker, Sevda; Yalinkilic, Ibrahim; Turkdogan, Kenan Ahmet

2017-01-01

Hyperbaric oxygen (HBO) treatment is steadily increasing as a therapeutic modality for various types of diseases. Although good clinical outcomes were reported with HBO treatment for various diseases, the multisystemic effects of this modality are still unclear. This study aimed to investigate the renal effects of HBO experimentally. Fourteen New Zealand White rabbits were divided into 2 groups randomly as the control group and the study group. The study group received HBO treatment for 28 days (100% oxygen at 2.5 atmospheres for 90 minutes daily) and the control group was used to obtain normal renal tissue of the animal genus. After the intervention period, venous blood samples were obtained, and renal tissue samples were harvested for comparisons. Normal histological morphology was determined with Masson trichrome staining and periodic acid-Schiff staining in the control group. Atrophic glomerular structures, vacuolated tubule cells, and degeneration were detected in the renal samples of the study group with Masson trichrome staining. Additionally, flattening was observed on the brush borders of the proximal tubules, and tubular dilatation was visualized with periodic acid-Schiff staining. The histopathologic disruption of renal morphology was verified with detection of significantly elevated kidney function laboratory biomarkers in the study group. Our findings suggests that HBO has adverse effects on renal glomerulus and proximal tubules. However, the functional effects of this alteration should be investigated with further studies.

Experimental lead poisoning in bald eagles

USGS Publications Warehouse

Pattee, H.; Wiemeyer, S.; Hoffman, P.; Carpenter, J.; Sileo, L.

1979-01-01

Captive, crippled bald eagles unsuitable for release were fed lead shot to determine diagnostic criteria for lead poisoning. The eagles were fluoroscoped and bled periodically to determine shot retention and blood delta--aminolevulinic acid dehydratase activity. Microscopic examination revealed renal tubular degeneration, arterial fibrinoid necrosis and myocardial necrosis. Acid-fast intra-nuclear inclusion bodies were not found in proximal convoluted tubule cells. Analyses of blood and toxicological data are not yet complete.

Experimental lead-shot poisoning in bald eagles

USGS Publications Warehouse

Pattee, O.H.; Wiemeyer, Stanley N.; Mulhern, B.M.; Sileo, L.; Carpenter, J.W.

1981-01-01

Captive, crippled bald eagles unsuitable for release were fed lead shot to determine diagnostic criteria for lead poisoning. The eagles were fluoroscoped and bled periodically to determine shot retention and blood delta--aminolevulinic acid dehydratase activity. Microscopic examination revealed renal tubular degeneration, arterial fibrinoid necrosis and myocardial necrosis. Acid-fast intra-nuclear inclusion bodies were not found in proximal convoluted tubule cells. Analyses of blood and toxicological data are not yet complete.

Primary proximal tubule injury leads to epithelial cell cycle arrest, fibrosis, vascular rarefaction, and glomerulosclerosis

PubMed Central

Bonventre, Joseph V

2014-01-01

Tubular injury has a major etiological role in fibrosis. For many years, this relationship has been dominated by the perception that epithelial cells are transformed into myofibroblasts that proliferate and generate fibrotic matrix—the so-called epithelial-to-mesenchymal transition. Here we focus on mechanisms by which injury to the tubule results in fibrosis because of paracrine mechanisms. Specific injury to the proximal tubule results in inflammation, reversible injury, and adaptive repair if the insult is mild, self-limited in time, and occurs in a background of a normal kidney. Repeated injury, in contrast, leads to maladaptive repair with sustained tubule injury, chronic inflammation, proliferation of interstitial myofibroblasts, vascular rarefaction, interstitial fibrosis, and glomerular sclerosis. During the maladaptive repair process after the renal insult, many tubular cells become arrested in the G2/M phase of the cell cycle. This results in activation of the DNA repair response with the resultant synthesis and secretion of pro-fibrotic factors. Pharmacologic interventions that enhance the movement through G2/M or facilitate apoptosis of cells that otherwise would be blocked in G2/M may reduce the development of fibrosis after kidney injury and reduce the progression of chronic kidney disease. PMID:26310195

Ochratoxin A induced premature senescence in human renal proximal tubular cells.

PubMed

Yang, Xuan; Liu, Sheng; Huang, Chuchu; Wang, Haomiao; Luo, Yunbo; Xu, Wentao; Huang, Kunlun

2017-05-01

Ochratoxin A (OTA) has many nephrotoxic effects and is a promising compound for the study of nephrotoxicity. Human renal proximal tubular cells (HKC) are an important model for the study of renal reabsorption, renal physiology and pathology. Since the induction of OTA in renal senescence is largely unknown, whether OTA can induce renal senescence, especially at a sublethal dose, and the mechanism of OTA toxicity remain unclear. In our study, a sublethal dose of OTA led to an enhanced senescent phenotype, β-galactosidase staining and senescence associated secretory phenotype (SASP). Cell cycle arrest and cell shape alternations also confirmed senescence. In addition, telomere analysis by RT-qPCR allowed us to classify OTA-induced senescence as a premature senescence. Western blot assays showed that the p53-p21 and the p16-pRB pathways and the ezrin-associated cell spreading changes were activated during the OTA-induced senescence of HKC. In conclusion, our results demonstrate that OTA promotes the senescence of HKC through the p53-p21 and p16-pRB pathways. The understanding of the mechanisms of OTA-induced senescence is critical in determining the role of OTA in cytotoxicity and its potential carcinogenicity. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Tuberin Inhibits Production of the Matrix Protein Fibronectin in Diabetes

PubMed Central

Yadav, Mukesh; Tizani, Shaza; Bhandari, Basant; Valente, Anthony J.

2012-01-01

Exposure of proximal tubular epithelial cells to high glucose contributes to the accumulation of tubulointerstitial and matrix proteins in diabetic nephropathy, but how this occurs is not well understood. We investigated the effect of the signaling molecule tuberin, which modulates the mammalian target of rapamycin pathway, on renal hypertrophy and fibronectin expression. We found that the kidney mass was significantly greater in partially tuberin-deficient (TSC2+/−) diabetic rats than wild-type diabetic rats. Furthermore, TSC2+/− rats exhibited significant increases in the basal levels of phospho-tuberin and fibronectin expression in the kidney cortex. Increased levels of phosphorylated tuberin associated with an increase in fibronectin expression in both wild-type and TSC2+/− diabetic rats. Treatment with insulin abrogated the diabetes-induced increase in fibronectin expression. In vitro, high glucose enhanced fibronectin expression in TSC2+/− primary proximal tubular epithelial cells; both inhibition of Akt and inhibition of the mammalian target of rapamycin could prevent this effect of glucose. In addition, forced expression of tuberin in tuberin-null cells abolished the expression of fibronectin protein. Taken together, these data suggest that tuberin plays a central role in the development of renal hypertrophy and in modulating the production of the matrix protein fibronectin in diabetes. PMID:22904348

Lack of effect of non-steroid antiinflammatory drugs on lithium clearance and on delivery of tubular fluid to the loop of Henle in rats.

PubMed

Lassen, E; Thomsen, K; Sørensen, S S; Pedersen, E B

1986-11-01

This paper examines a possible interaction between non-steroid antiinflammatory drugs (NSAI drugs) and renal lithium clearance in conscious, unoperated rats with diabetes insipidus (Brattleboro strain) and ordinary Wistar rats. The drugs were given with the food for 5 days before clearance determinations in the following daily doses per kg body weight: acetylsalicyclic acid 115 mg/kg, phenylbutazone 20 mg/kg, indomethacin 5 mg/kg, and penicillamine 65 mg/kg. None of the drugs affected the lithium clearance. Also urine flow, sodium clearance, potassium clearance, and prostaglandin E2 excretion remained unaffected by the treatments. The results suggest that a continued lowering of lithium clearance cannot be produced, at least not by administration of the drugs with the food. Since lithium clearance is a quantitative measure of the delivery of tubular fluid from the proximal tubules to the loop of Henle, the results also suggest that chronic administration of NSAI drugs does not influence delivery from the proximal tubules in rats. The lowering of lithium clearance observed by others after administration of the drugs by injection or by gastric tube may have been transient, lasting only for a short period after each administration.

Heat shock factor 1 induces crystallin-αB to protect against cisplatin nephrotoxicity

PubMed Central

Lou, Qiang; Hu, Yanzhong; Ma, Yuanfang

2016-01-01

Cisplatin, a wildly used chemotherapy drug, induces nephrotoxicity that is characterized by renal tubular cell apoptosis. In response to toxicity, tubular cells can activate cytoprotective mechanisms, such as the heat shock response. However, the role and regulation of the heat shock response in cisplatin-induced nephrotoxicity remain largely unclear. In the present study, we demonstrated the induction of heat shock factor (Hsf)1 and the small heat shock protein crystallin-αB (CryAB) during cisplatin nephrotoxicity in mice. Consistently, cisplatin induced Hsf1 and CryAB in a cultured renal proximal tubular cells (RPTCs). RPTCs underwent apoptosis during cisplatin treatment, which was increased when Hsf1 was knocked down. Transfection or restoration of Hsf1 into Hsf1 knockdown cells suppressed cisplatin-induced apoptosis, further supporting a cytoprotective role of Hsf1 and its associated heat shock response. Moreover, Hsf1 knockdown increased Bax translocation to mitochondria and cytochrome c release into the cytosol. In RPTCs, Hsf1 knockdown led to a specific downregulation of CryAB. Transfection of CryAB into Hsf1 knockdown cells diminished their sensitivity to cisplatin-induced apoptosis, suggesting that CryAB may be a key mediator of the cytoprotective effect of Hsf1. Taken together, these results demonstrate a heat shock response in cisplatin nephrotoxicity that is mediated by Hsf1 and CryAB to protect tubular cells against apoptosis. PMID:27194715

The volatile anesthetic isoflurane induces ecto-5′-nucleotidase (CD73) to protect against renal ischemia and reperfusion injury

PubMed Central

Kim, Mihwa; Ham, Ahrom; Kim, Joo Yun; Brown, Kevin M.; D’Agati, Vivette D.; Lee, H. Thomas

2013-01-01

The volatile anesthetic isoflurane protects against renal ischemia and reperfusion injury by releasing renal tubular TGF-β1. Since adenosine is a powerful cytoprotective molecule, we tested whether TGF-β1 generated by isoflurane induces renal tubular ecto-5′-nucleotidase (CD73) and adenosine to protect against renal ischemia and reperfusion injury. Isoflurane induced new CD73 synthesis and increased adenosine generation in cultured kidney proximal tubule cells and in mouse kidney. Moreover, a TGF-β1 neutralizing antibody prevented isoflurane-mediated induction of CD73 activity. Mice anesthetized with isoflurane after renal ischemia and reperfusion had significantly reduced plasma creatinine and decreased renal tubular necrosis, neutrophil infiltration and apoptosis compared to pentobarbital-anesthetized mice. Isoflurane failed to protect against renal ischemia and reperfusion injury in CD73 deficient mice, in mice pretreated with a selective CD73 inhibitor or mice treated with an adenosine receptor antagonist. The TGF-β1 neutralizing antibody or the CD73 inhibitor attenuated isoflurane-mediated protection against HK-2 cell apoptosis. Thus, isoflurane causes TGF-β1-dependent induction of renal tubular CD73 and adenosine generation to protect against renal ischemia and reperfusion injury. Modulation of this pathway may have important therapeutic implications to reduce morbidity and mortality arising from ischemic acute kidney injury. PMID:23423261

Aquatic models for the study of renal transport function and pollutant toxicity.

PubMed Central

Miller, D S

1987-01-01

Studies of renal cell transport mechanisms and their impairment by xenobiotics are often limited by technical difficulties related to renal tubule complexity. Problems include the juxtaposition of multiple tubule segments with different transport functions and severely limited access to the tubular lumen. Some limitations can be overcome by the careful selection of an appropriate aquatic experimental system. Two aquatic models for the vertebrate proximal segment are discussed here. The first is the kidney from certain marine flounder, which offers the following advantages: long-term viability, little tissue of nonproximal origin, and easy tubule isolation. Data are presented to demonstrate how studies with flounder kidney can be used to elucidate cellular mechanisms whereby different classes of toxic pollutants may interact. Results from these experiments indicate that the excretion of certain anionic xenobiotics can be delayed by other anionic xenobiotics that compete for secretory transport sites and by compounds that disrupt cellular ion gradients and energy metabolism needed to drive transport. The second system is the crustacean urinary bladder, a simple, flatsheet epithelium. Bladder morphology and transport physiology closely resemble those of vertebrate proximal segment. Electron micrographs show a brush border membrane at the luminal surface, numerous mitochondria, and an infolded serosal membrane, while in vivo and in vitro transport studies show reabsorption of NaCl, nutrients and water and secretion of organic cations; organic anions are secreted in bladders from some species and reabsorbed in others. Moreover, since bladders can be mounted as flat sheets in flux chambers, studies with this tissue avoid the problems of complex renal tubule geometry and tissue heterogeneity that limit transport studies in proximal tubule. Images FIGURE 3. FIGURE 6. PMID:3297665

A New Pathogenesis of Albuminuria: Role of Transcytosis.

PubMed

He, Fang-Fang; Gong, Yi; Li, Zhen-Qiong; Wu, Liang; Jiang, Hua-Jun; Su, Hua; Zhang, Chun; Wang, Yu-Mei

2018-06-15

Transcytosis is an important intracellular transport process by which multicellular organisms selectively move cargoes from apical to basolateral membranes without disrupting cellular homeostasis. In kidney, macromolecular components in the serum, such as albumin, low-density lipoprotein and immunoglobulins, pass through the glomerular filtration barrier (GFB) and proximal tubular cells (PTCs) by transcytosis. Protein transcytosis plays a vital role in the pathology of albuminuria, which causes progressive destruction of the GFB structure and function. However, the pathophysiological consequences of protein transcytosis in the kidney remain largely unknown. This article summarizes recent researches on the regulation of albumin transcytosis across the GFB and PTCs in both physiological and pathological conditions. Understanding the mechanism of albumin transcytosis may reveal potential therapeutic targets for prevention or alleviation of the pathological consequences of albuminuria. © 2018 The Author(s). Published by S. Karger AG, Basel.

Brief Report: Long-Term (96-Week) Efficacy and Safety After Switching From Tenofovir Disoproxil Fumarate to Tenofovir Alafenamide in HIV-Infected, Virologically Suppressed Adults

PubMed Central

Raffi, François; Orkin, Chloe; Clarke, Amanda; Slama, Laurence; Gallant, Joel; Daar, Eric; Henry, Keith; Santana-Bagur, Jorge; Stein, David K.; Bellos, Nicholaos; Scarsella, Anthony; Yan, Mingjin; Abram, Michael E.; Cheng, Andrew

2017-01-01

Abstract: In a double-blind, phase 3 trial, 663 HIV-infected, virologically suppressed adults were randomized to switch to tenofovir alafenamide (TAF; n = 333) vs. remain on tenofovir disoproxil fumarate (TDF; n = 330), each coformulated with emtricitabine (FTC), while continuing their third agent (boosted protease inhibitor or unboosted third agent). At week 96, 88.6% on FTC/TAF and 89.1% on FTC/TDF had HIV-1 RNA <50 copies per milliliter [adjusted difference −0.5% (95% confidence interval: −5.3 to 4.4%)]. Proteinuria, albuminuria, proximal renal tubular function, and bone mineral density improved after switching to TAF- from TDF-containing regimens. These longer-term data support FTC/TAF as a safe, well-tolerated, and durable nucleotide reverse transcriptase inhibitor backbone. PMID:28272164

In vivo imaging of kidney glomeruli transplanted into the anterior chamber of the mouse eye

PubMed Central

Kistler, Andreas D.; Caicedo, Alejandro; Abdulreda, Midhat H.; Faul, Christian; Kerjaschki, Dontscho; Berggren, Per-Olof; Reiser, Jochen; Fornoni, Alessia

2014-01-01

Multiphoton microscopy enables live imaging of the renal glomerulus. However, repeated in vivo imaging of the same glomerulus over extended periods of time and the study of glomerular function independent of parietal epithelial and proximal tubular cell effects has not been possible so far. Here, we report a novel approach for non-invasive imaging of acapsular glomeruli transplanted into the anterior chamber of the mouse eye. After microinjection, glomeruli were capable of engrafting on the highly vascularized iris. Glomerular structure was preserved, as demonstrated by podocyte specific expression of cyan fluorescent protein and by electron microscopy. Injection of fluorescence-labeled dextrans of various molecular weights allowed visualization of glomerular filtration and revealed leakage of 70 kDa dextran in an inducible model of proteinuria. Our findings demonstrate functionality and long-term survival of glomeruli devoid of Bowman's capsule and provide a novel approach for non-invasive longitudinal in vivo study of glomerular physiology and pathophysiology. PMID:24464028

Renal tubular function in children with tyrosinaemia type I treated with nitisinone.

PubMed

Santra, S; Preece, M A; Hulton, S-A; McKiernan, P J

2008-06-01

Tyrosinaemia type I (TTI) is an inherited deficiency in the enzyme fumarylacetoacetate hydrolase and is frequently complicated by renal tubular dysfunction which may persist in some patients after hepatic transplantation. Nitisinone has revolutionized the management of TTI but its effect on renal tubular dysfunction has not been described in a large cohort of patients. To document the incidence and progression of renal tubular dysfunction in children with TTI treated with nitisinone at a single centre. Twenty-one patients with TTI from a single centre were treated with nitisinone for at least 12 months. Median age at first treatment was 17 weeks (range 1 week to 27 months). Nine patients (43%) presented in acute liver failure, seven (33%) had a chronic presentation and five (24%) were detected pre-clinically. A retrospective case analysis of plasma phosphate, urinary protein/creatinine ratio and tubular reabsorption of phosphate was performed for all patients as markers of tubular function. Renal ultrasounds were examined for evidence of nephrocalcinosis and where available, skeletal radiographs for rickets. All patients had biochemical evidence of renal tubular dysfunction at presentation. After nitisinone and dietary treatment were started, all three markers normalized within one year. Four children had clinical rickets at presentation (which improved), of whom one had nephrocalcinosis, which did not reverse on nitisinone. No child redeveloped tubular dysfunction after commencing nitisinone. All patients with TTI had evidence of tubular dysfunction at presentation and in all cases this resolved with nitisinone and dietary control. The tubulopathy associated with TTI is reversible.

The Mitochondria-Targeted Antioxidant Mitoquinone Protects against Cold Storage Injury of Renal Tubular Cells and Rat Kidneys

PubMed Central

Mitchell, Tanecia; Rotaru, Dumitru; Saba, Hamida; Smith, Robin A. J.; Murphy, Michael P.

2011-01-01

The majority of kidneys used for transplantation are obtained from deceased donors. These kidneys must undergo cold preservation/storage before transplantation to preserve tissue quality and allow time for recipient selection and transport. However, cold storage (CS) can result in tissue injury, kidney discardment, or long-term renal dysfunction after transplantation. We have previously determined mitochondrial superoxide and other downstream oxidants to be important signaling molecules that contribute to CS plus rewarming (RW) injury of rat renal proximal tubular cells. Thus, this study's purpose was to determine whether adding mitoquinone (MitoQ), a mitochondria-targeted antioxidant, to University of Wisconsin (UW) preservation solution could offer protection against CS injury. CS was initiated by placing renal cells or isolated rat kidneys in UW solution alone (4 h at 4°C) or UW solution containing MitoQ or its control compound, decyltriphenylphosphonium bromide (DecylTPP) (1 μM in vitro; 100 μM ex vivo). Oxidant production, mitochondrial function, cell viability, and alterations in renal morphology were assessed after CS exposure. CS induced a 2- to 3-fold increase in mitochondrial superoxide generation and tyrosine nitration, partial inactivation of mitochondrial complexes, and a significant increase in cell death and/or renal damage. MitoQ treatment decreased oxidant production ∼2-fold, completely prevented mitochondrial dysfunction, and significantly improved cell viability and/or renal morphology, whereas DecylTPP treatment did not offer any protection. These findings implicate that MitoQ could potentially be of therapeutic use for reducing organ preservation damage and kidney discardment and/or possibly improving renal function after transplantation. PMID:21159749

The mitochondria-targeted antioxidant mitoquinone protects against cold storage injury of renal tubular cells and rat kidneys.

PubMed

Mitchell, Tanecia; Rotaru, Dumitru; Saba, Hamida; Smith, Robin A J; Murphy, Michael P; MacMillan-Crow, Lee Ann

2011-03-01

The majority of kidneys used for transplantation are obtained from deceased donors. These kidneys must undergo cold preservation/storage before transplantation to preserve tissue quality and allow time for recipient selection and transport. However, cold storage (CS) can result in tissue injury, kidney discardment, or long-term renal dysfunction after transplantation. We have previously determined mitochondrial superoxide and other downstream oxidants to be important signaling molecules that contribute to CS plus rewarming (RW) injury of rat renal proximal tubular cells. Thus, this study's purpose was to determine whether adding mitoquinone (MitoQ), a mitochondria-targeted antioxidant, to University of Wisconsin (UW) preservation solution could offer protection against CS injury. CS was initiated by placing renal cells or isolated rat kidneys in UW solution alone (4 h at 4°C) or UW solution containing MitoQ or its control compound, decyltriphenylphosphonium bromide (DecylTPP) (1 μM in vitro; 100 μM ex vivo). Oxidant production, mitochondrial function, cell viability, and alterations in renal morphology were assessed after CS exposure. CS induced a 2- to 3-fold increase in mitochondrial superoxide generation and tyrosine nitration, partial inactivation of mitochondrial complexes, and a significant increase in cell death and/or renal damage. MitoQ treatment decreased oxidant production ~2-fold, completely prevented mitochondrial dysfunction, and significantly improved cell viability and/or renal morphology, whereas DecylTPP treatment did not offer any protection. These findings implicate that MitoQ could potentially be of therapeutic use for reducing organ preservation damage and kidney discardment and/or possibly improving renal function after transplantation.

Uromodulin retention in thick ascending limb of Henle's loop affects SCD1 in neighboring proximal tubule: renal transcriptome studies in mouse models of uromodulin-associated kidney disease.

PubMed

Horsch, Marion; Beckers, Johannes; Fuchs, Helmut; Gailus-Durner, Valérie; Hrabě de Angelis, Martin; Rathkolb, Birgit; Wolf, Eckhard; Aigner, Bernhard; Kemter, Elisabeth

2014-01-01

Uromodulin-associated kidney disease (UAKD) is a hereditary progressive renal disease which can lead to renal failure and requires renal replacement therapy. UAKD belongs to the endoplasmic reticulum storage diseases due to maturation defect of mutant uromodulin and its retention in the enlarged endoplasmic reticulum in the cells of the thick ascending limb of Henle's loop (TALH). Dysfunction of TALH represents the key pathogenic mechanism of UAKD causing the clinical symptoms of this disease. However, the molecular alterations underlying UAKD are not well understood. In this study, transcriptome profiling of whole kidneys of two mouse models of UAKD, UmodA227T and UmodC93F, was performed. Genes differentially abundant in UAKD affected kidneys of both Umod mutant lines at different disease stages were identified and verified by RT-qPCR. Additionally, differential protein abundances of SCD1 and ANGPTL7 were validated by immunohistochemistry and Western blot analysis. ANGPTL7 expression was down-regulated in TALH cells of Umod mutant mice which is the site of the mutant uromodulin maturation defect. SCD1 was expressed selectively in the S3 segment of proximal tubule cells, and SCD1 abundance was increased in UAKD affected kidneys. This finding demonstrates that a cross talk between two functionally distinct tubular segments of the kidney, the TALH segment and the S3 segment of proximal tubule, exists.

Comparative ultrastructure of coxal glands in unfed larvae of Leptotrombidium orientale (Schluger, 1948) (Trombiculidae) and Hydryphantes ruber (de Geer, 1778) (Hydryphantidae).

PubMed

Shatrov, Andrey B

2017-11-01

Coxal glands of unfed larvae Leptotrombidium orientale (Schluger, 1948) (Trombiculidae), a terrestrial mite parasitizing vertebrates, and Hydryphantes ruber (de Geer, 1778) (Hydryphantidae), a water mite parasitizing insects were studied using transmission electron microscopy. In both species, the coxal glands are represented by a paired tubular organ extending on the sides of the brain from the mouthparts to the frontal midgut wall and are formed of the cells arranged around the central lumen. As in other Parasitengona, the coxal glands are devoid of a proximal sacculus. The excretory duct, joining with ducts of the prosomal salivary glands constitutes the common podocephalic duct, opening into the subcheliceral space. The coxal glands of L. orientale are composed of a distal tubule with a basal labyrinth, an intermediate segment without labyrinth, and a proximal tubule bearing tight microvilli on the apical cell surface and coiled around the intermediate segment. The coxal glands of H. ruber mainly consist of the uniformly organized proximal tubule with apical microvilli of the cells lacking the basal labyrinth. This tubule shows several loops running backward and forward in a vertical plane on the side of the brain. In contrast to L. orientale, larvae of H. ruber reveal a terminal cuticular sac/bladder for accumulation of secreted fluids. Organization of the coxal glands depends on the ecological conditions of mites. Larvae of terrestrial L. orientale possess distal tubule functioning in re-absorption of ions and water. Conversely, water mite larvae H. ruber need to evacuate of the water excess, so the filtrating proximal tubule is prominent. © 2017 Wiley Periodicals, Inc.

The renal effects of SGLT2 inhibitors and a mini-review of the literature.

PubMed

Andrianesis, Vasileios; Glykofridi, Spyridoula; Doupis, John

2016-12-01

Sodium-glucose linked transporter 2 (SGLT2) inhibitors are a new and promising class of antidiabetic agents which target renal tubular glucose reabsorption. Their action is based on the blockage of SGLT2 sodium-glucose cotransporters that are located at the luminal membrane of tubular cells of the proximal convoluted tubule, inducing glucosuria. It has been proven that they significantly reduce glycated hemoglobin (HbA1c), along with fasting and postprandial plasma glucose in patients with type 2 diabetes mellitus (T2DM). The glucosuria-induced caloric loss as well as the osmotic diuresis significantly decrease body weight and blood pressure, respectively. Given that SGLT2 inhibitors do not interfere with insulin action and secretion, their efficacy is sustained despite the progressive β-cell failure in T2DM. They are well tolerated, with a low risk of hypoglycemia. Their most frequent adverse events are minor: genital and urinal tract infections. Recently, it was demonstrated that empagliflozin presents a significant cardioprotective effect. Although the SGLT2 inhibitors' efficacy is affected by renal function, new data have been presented that some SGLT2 inhibitors, even in mild and moderate renal impairment, induce significant HbA1c reduction. Moreover, recent data indicate that SGLT2 inhibition has a beneficial renoprotective effect. The role of this review paper is to explore the current evidence on the renal effects of SGLT2 inhibitors.

The renal effects of SGLT2 inhibitors and a mini-review of the literature

PubMed Central

Andrianesis, Vasileios; Glykofridi, Spyridoula; Doupis, John

2016-01-01

Sodium-glucose linked transporter 2 (SGLT2) inhibitors are a new and promising class of antidiabetic agents which target renal tubular glucose reabsorption. Their action is based on the blockage of SGLT2 sodium-glucose cotransporters that are located at the luminal membrane of tubular cells of the proximal convoluted tubule, inducing glucosuria. It has been proven that they significantly reduce glycated hemoglobin (HbA1c), along with fasting and postprandial plasma glucose in patients with type 2 diabetes mellitus (T2DM). The glucosuria-induced caloric loss as well as the osmotic diuresis significantly decrease body weight and blood pressure, respectively. Given that SGLT2 inhibitors do not interfere with insulin action and secretion, their efficacy is sustained despite the progressive β-cell failure in T2DM. They are well tolerated, with a low risk of hypoglycemia. Their most frequent adverse events are minor: genital and urinal tract infections. Recently, it was demonstrated that empagliflozin presents a significant cardioprotective effect. Although the SGLT2 inhibitors’ efficacy is affected by renal function, new data have been presented that some SGLT2 inhibitors, even in mild and moderate renal impairment, induce significant HbA1c reduction. Moreover, recent data indicate that SGLT2 inhibition has a beneficial renoprotective effect. The role of this review paper is to explore the current evidence on the renal effects of SGLT2 inhibitors. PMID:28203358

Epidermal Growth Factor Receptor Inhibition with Erlotinib Partially Prevents Cisplatin-Induced Nephrotoxicity in Rats

PubMed Central

Matsumoto, Kei; Shindo-Hirai, Yuki; Kuno, Yoshihiro; Yamamoto, Yasutaka; Suzuki, Taihei; Saito, Tomohiro; Iseri, Ken; Shibata, Takanori

2014-01-01

The effects of blocking the epidermal growth factor receptor (EGFR) in acute kidney injury (AKI) are controversial. Here we investigated the renoprotective effect of erlotinib, a selective tyrosine kinase inhibitor that can block EGFR activity, on cisplatin (CP)-induced AKI. Groups of animals were given either erlotinib or vehicle from one day before up to Day 3 following induction of CP- nephrotoxicity (CP-N). In addition, we analyzed the effects of erlotinib on signaling pathways involved in CP-N by using human renal proximal tubular cells (HK-2). Compared to controls, rats treated with erlotinib exhibited significant improvement of renal function and attenuation of tubulointerstitial injury, and reduced the number of apoptotic and proliferating cells. Erlotinib-treated rats had a significant reduction of renal cortical mRNA for profibrogenic genes. The Bax/Bcl-2 mRNA and protein ratios were significantly reduced by erlotinib treatment. In vitro, we observed that erlotinib significantly reduced the phosphorylation of MEK1 and Akt, processes that were induced by CP in HK-2. Taken together, these data indicate that erlotinib has renoprotective properties that are likely mediated through decreases in the apoptosis and proliferation of tubular cells, effects that reflect inhibition of downstream signaling pathways of EGFR. These results suggest that erlotinib may be useful for preventing AKI in patients receiving CP chemotherapy. PMID:25390346

Liquid-phase chromatography detector

DOEpatents

Voigtman, E.G.; Winefordner, J.D.; Jurgensen, A.R.

1983-11-08

A liquid-phase chromatography detector comprises a flow cell having an inlet tubular conduit for receiving a liquid chromatographic effluent and discharging it as a flowing columnar stream onto a vertically adjustable receiving surface spaced apart from and located vertically below and in close proximity to the discharge end of the tubular conduit; a receiver adapted to receive liquid overflowing from the receiving surface; an exit conduit for continuously removing liquid from the receiver; a light source for focusing fluorescence-producing light pulses on the flowing columnar stream as it passes from the outlet of the conduit to the receiving surface and a fluorescence detector to detect the produced fluorescence; a source of light pulse for producing acoustic waves in the columnar stream as it passes from the conduit outlet to the receiving surface; and a piezoelectric transducer adapted to detect those waves; and a source of bias voltage applied to the inlet tubular conduit and adapted to produce ionization of the liquid flowing through the flow cell so as to produce photocurrents therein and an electrical system to detect and record the photocurrents. This system is useful in separating and detecting individual chemical compounds from mixtures thereof. 5 figs.

Kidney and Phosphate Metabolism

PubMed Central

2008-01-01

The serum phosphorus level is maintained through a complex interplay between intestinal absorption, exchange intracellular and bone storage pools, and renal tubular reabsorption. The kidney plays a major role in regulation of phosphorus homeostasis by renal tubular reabsorption. Type IIa and type IIc Na+/Pi transporters are important renal Na+-dependent inorganic phosphate (Pi) transporters, which are expressed in the brush border membrane of proximal tubular cells. Both are regulated by dietary Pi intake, vitamin D, fibroblast growth factor 23 (FGF23) and parathyroid hormone. The expression of type IIa Na+/Pi transporter result from hypophosphatemia quickly. However, type IIc appears to act more slowly. Physiological and pathophysiological alteration in renal Pi reabsorption are related to altered brush border membrane expression/content of the type II Na+/Pi cotransporter. Many studies of genetic and acquired renal phosphate wasting disorders have led to the identification of novel genes. Two novel Pi regulating genes, PHEX and FGF23, play a role in the pathophysiology of genetic and acquired renal phosphate wasting disorders and studies are underway to define their mechanism on renal Pi regulation. In recent studies, sodium-hydrogen exchanger regulatory factor 1 (NHERF1) is reported as another new regulator for Pi reabsorption mechanism. PMID:24459526

Liquid-phase chromatography detector

DOEpatents

Voigtman, Edward G.; Winefordner, James D.; Jurgensen, Arthur R.

1983-01-01

A liquid-phase chromatography detector comprising a flow cell having an inlet tubular conduit for receiving a liquid chromatographic effluent and discharging it as a flowing columnar stream onto a vertically adjustable receiving surface spaced apart from and located vertically below and in close proximity to the discharge end of the tubular conduit; a receiver adapted to receive liquid overflowing from the receiving surface; an exit conduit for continuously removing liquid from the receiver; a light source for focussing fluorescence-producing light pulses on the flowing columnar stream as it passes from the outlet of the conduit to the receiving surface and a fluorescence detector to detect the produced fluorescence; a source of light pulse for producing acoustic waves in the columnar stream as it passes from the conduit outlet to the receiving surface; and a piezoelectric transducer adapted to detect those waves; and a source of bias voltage applied to the inlet tubular conduit and adapted to produce ionization of the liquid flowing through the flow cell so as to produce photocurrents therein and an electrical system to detect and record the photocurrents. This system is useful in separating and detecting individual chemical compounds from mixtures thereof.

Intracellular Kinases Mediate Increased Translation and Secretion of Netrin-1 from Renal Tubular Epithelial Cells

PubMed Central

Jayakumar, Calpurnia; Mohamed, Riyaz; Ranganathan, Punithavathi Vilapakkam; Ramesh, Ganesan

2011-01-01

Background Netrin-1 is a laminin-related secreted protein, is highly induced after tissue injury, and may serve as a marker of injury. However, the regulation of netrin-1 production is not unknown. Current study was carried out in mouse and mouse kidney cell line (TKPTS) to determine the signaling pathways that regulate netrin-1 production in response to injury. Methods and Principal Findings Ischemia reperfusion injury of the kidney was induced in mice by clamping renal pedicle for 30 minutes. Cellular stress was induced in mouse proximal tubular epithelial cell line by treating with pervanadate, cisplatin, lipopolysaccharide, glucose or hypoxia followed by reoxygenation. Netrin-1 expression was quantified by real time RT-PCR and protein production was quantified using an ELISA kit. Cellular stress induced a large increase in netrin-1 production without increase in transcription of netrin-1 gene. Mitogen activated protein kinase, ERK mediates the drug induced netrin-1 mRNA translation increase without altering mRNA stability. Conclusion Our results suggest that netrin-1 expression is suppressed at the translational level and MAPK activation leads to rapid translation of netrin-1 mRNA in the kidney tubular epithelial cells. PMID:22046354

Albumin stimulates renal tubular inflammation through an HSP70-TLR4 axis in mice with early diabetic nephropathy

PubMed Central

Jheng, Huei-Fen; Tsai, Pei-Jane; Chuang, Yi-Lun; Shen, Yi-Ting; Tai, Ting-An; Chen, Wen-Chung; Chou, Chuan-Kai; Ho, Li-Chun; Tang, Ming-Jer; Lai, Kuei-Tai A.; Sung, Junne-Ming; Tsai, Yau-Sheng

2015-01-01

ABSTRACT Increased urinary albumin excretion is not simply an aftermath of glomerular injury, but is also involved in the progression of diabetic nephropathy (DN). Whereas Toll-like receptors (TLRs) are incriminated in the renal inflammation of DN, whether and how albumin is involved in the TLR-related renal inflammatory response remains to be clarified. Here, we showed that both TLR2 and TLR4, one of their putative endogenous ligands [heat shock protein 70 (HSP70)] and nuclear factor-κB promoter activity were markedly elevated in the kidneys of diabetic mice. A deficiency of TLR4 but not of TLR2 alleviated albuminuria, tubulointerstitial fibrosis and inflammation induced by diabetes. The protection against renal injury in diabetic Tlr4−/− mice was associated with reduced tubular injuries and preserved cubilin levels, rather than amelioration of glomerular lesions. In vitro studies revealed that albumin, a stronger inducer than high glucose (HG), induced the release of HSP70 from proximal tubular cells. HSP70 blockade ameliorated albumin-induced inflammatory mediators. HSP70 triggered the production of inflammatory mediators in a TLR4-dependent manner. Moreover, HSP70 inhibition in vivo ameliorated diabetes-induced albuminuria, inflammatory response and tubular injury. Finally, we found that individuals with DN had higher levels of TLR4 and HSP70 in the dilated tubules than non-diabetic controls. Thus, activation of the HSP70-TLR4 axis, stimulated at least in part by albumin, in the tubular cell is a newly identified mechanism associated with induction of tubulointerstitial inflammation and aggravation of pre-existing microalbuminuria in the progression of DN. PMID:26398934

Apelin attenuates TGF-β1-induced epithelial to mesenchymal transition via activation of PKC-ε in human renal tubular epithelial cells.

PubMed

Wang, Li-Yan; Diao, Zong-Li; Zheng, Jun-Fang; Wu, Yi-Ru; Zhang, Qi-Dong; Liu, Wen-Hu

2017-10-01

Epithelial to mesenchymal transition (EMT), a process whereby fully differentiated epithelial cells transition to a mesenchymal phenotype, has been implicated in the pathogenesis of renal fibrosis. Apelin, a bioactive peptide, has recently been recognized to protect against renal profibrotic activity, but the underlying mechanism has not yet been elucidated. In this study, we investigated the regulation of EMT in the presence of apelin-13 in vitro. Expression of the mesenchymal marker alpha-smooth muscle actin (α-SMA) and the epithelial marker E-cadherin was examined by immunofluorescence and western blotting in transforming growth factor beta 1 (TGF-β1)-stimulated human proximal tubular epithelial cells. Expression of extracellular matrix, fibronectin and collagen-I was examined by quantitative real-time PCR and ELISA. F13A, an antagonist of the apelin receptor APJ, and small interfering RNA targeting protein kinase C epsilon (PKC-ε) were used to explore the relevant signaling pathways. Apelin attenuated TGF-β1-induced EMT, and inhibited the EMT-associated increase in α-SMA, loss of E-cadherin, and secretion of extracellular matrix. Moreover, apelin activated PKC-ε in tubular epithelial cells, which in turn decreased phospho-Smad2/3 levels and increased Smad-7 levels. APJ inhibition or PKC-ε deletion diminished apelin-induced modulation of Smad signaling and suppression of tubular EMT. Our findings identify a novel PKC-ε-dependent mechanism in which apelin suppresses TGF-β1-mediated activation of Smad signaling pathways and thereby inhibits tubular EMT. These results suggest that apelin may be a new agent that can suppress renal fibrosis and retard chronic kidney disease progression. Copyright © 2017 Elsevier Inc. All rights reserved.

Acute thiamine deficiency and refeeding syndrome: Similar findings but different pathogenesis.

PubMed

Maiorana, Arianna; Vergine, Gianluca; Coletti, Valentina; Luciani, Matteo; Rizzo, Cristiano; Emma, Francesco; Dionisi-Vici, Carlo

2014-01-01

Refeeding syndrome can occur in several contexts of relative malnutrition in which an overaggressive nutritional support is started. The consequences are life threatening with multiorgan impairment, and severe electrolyte imbalances. During refeeding, glucose-involved insulin secretion causes abrupt reverse of lipolysis and a switch from catabolism to anabolism. This creates a sudden cellular demand for electrolytes (phosphate, potassium, and magnesium) necessary for synthesis of adenosine triphosphate, glucose transport, and other synthesis reactions, resulting in decreased serum levels. Laboratory findings and multiorgan impairment similar to refeeding syndrome also are observed in acute thiamine deficiency. The aim of this study was to determine whether thiamine deficiency was responsible for the electrolyte imbalance caused by tubular electrolyte losses. We describe two patients with leukemia who developed acute thiamine deficiency with an electrolyte pattern suggestive of refeeding syndrome, severe lactic acidosis, and evidence of proximal renal tubular dysfunction. A single thiamine administration led to rapid resolution of the tubular dysfunction and normalization of acidosis and electrolyte imbalance. This demonstrated that thiamine deficiency was responsible for the electrolyte imbalance, caused by tubular electrolyte losses. Our study indicates that, despite sharing many laboratory similarities, refeeding syndrome and acute thiamine deficiency should be viewed as separate entities in which the electrolyte abnormalities reported in cases of refeeding syndrome with thiamine deficiency and refractory lactic acidosis may be due to renal tubular losses instead of a shifting from extracellular to intracellular compartments. In oncologic and malnourished patients, individuals at particular risk for developing refeeding syndrome, in the presence of these biochemical abnormalities, acute thiamine deficiency should be suspected and treated because it promptly responds to thiamine administration. Copyright © 2014 Elsevier Inc. All rights reserved.

Long-term followup of visual internal urethrotomy for management of short (less than 1 cm) penile urethral strictures following hypospadias repair.

PubMed

Husmann, D A; Rathbun, S R

2006-10-01

We reviewed the results of direct vision urethrotomy for short (less than 1 cm) penile urethral strictures following hypospadias surgery. Patients with less than 1 cm anterior penile urethral strictures located proximal to the meatus underwent direct vision urethrotomy. Based on the type of initial urethroplasty patients were randomly divided into treatment with direct vision urethrotomy vs direct vision urethrotomy plus clean intermittent catheterization for 3 months. Success was defined as absent obstructive voiding symptoms and a normal urine flow 2 years following the last patient instrumentation. Of patients with urethral strictures following hypospadias repair 44% (32) had previously undergone tubularized graft urethroplasty and 56% (40) had previously undergone flap urethroplasty, including a tubularized island flap in 18, an onlay flap in 11 and urethral plate urethroplasty in 11. Direct vision urethrotomy alone was performed in 51% of patients (37), and direct vision urethrotomy and clean intermittent catheterization were performed in 49% (35). Success with the 2 methods was similar, that is 24% (9 of 37 patients) vs 22% (8 of 35). Following direct vision urethrotomy all patients with tubularized graft urethroplasty showed failure (0 of 32). Success was noted in 11% of patients (2 of 18) with tubularized island flap urethroplasty compared to 72% (8 of 11) with onlay urethroplasty and 63% (7 of 11) with urethral plate urethroplasty (each p <0.05). The addition of clean intermittent catheterization to direct vision urethrotomy does not improve the likelihood of success. Direct vision urethrotomy for short (less than 1 cm) urethral stricture usually fails following any type of tubularized graft or flap urethroplasty but it had moderate success following onlay flap and urethral plate urethroplasties.

Effects of shiga toxin 2 on cellular regeneration mechanisms in primary and three-dimensional cultures of human renal tubular epithelial cells.

PubMed

Márquez, Laura B; Araoz, Alicia; Repetto, Horacio A; Ibarra, Fernando R; Silberstein, Claudia

2016-10-01

Shiga toxin (Stx)-producing Escherichia coli (STEC) causes post-diarrheal Hemolytic Uremic Syndrome (HUS), which is one of the most common causes of acute renal failure in children in Argentine. The aim of the present work was to study the effects of Shiga toxin type 2 (Stx2) on regenerative mechanisms of primary cultures of human cortical renal tubular epithelial cells (HRTEC) and three-dimensional (3D) cultures of HRTEC. Primary cultures of HRTEC were able to develop tubular structures when grown in matrigel, which showed epithelial cells surrounding a central lumen resembling the original renal tubules. Exposure to Stx2 inhibited tubulogenesis in 3D-HRTEC cultures. Moreover, a significant increase in apoptosis, and decrease in cell proliferation was observed in tubular structures of 3D-HRTEC exposed to Stx2. A significant reduction in cell migration and vimentin expression levels was observed in HRTEC primary cultures exposed to Stx2, demonstrating that the holotoxin affected HRTEC dedifferentiation. Furthermore, a decreased number of cells expressing CD133 progenitor marker was found in HRTEC cultures treated with Stx2. The CD133 positive cells also expressed the Stx receptor globotriaosylceramide, which may explain their sensitivity to Stx2. In conclusion, Stx2 affects the regenerative processes of human renal tubular epithelial cells in vitro, by inhibiting cell dedifferentiation mechanisms, as well as tubules restoration. The development of 3D-HRTEC cultures that resemble original human renal proximal tubules is a novel in vitro model to study renal epithelial repair mechanisms after injury. Copyright © 2016 Elsevier Ltd. All rights reserved.

DNA damage response in renal ischemia-reperfusion and ATP-depletion injury of renal tubular cells

PubMed Central

Ma, Zhengwei; Wei, Qingqing; Dong, Guie; Huo, Yuqing; Dong, Zheng

2014-01-01

Renal ischemia-reperfusion leads to acute kidney injury (AKI) that is characterized pathologically by tubular damage and cell death, followed by tubular repair, atrophy and interstitial fibrosis. Recent work suggested the possible presence of DNA damage response (DDR) in AKI. However, the evidence is sketchy and the role and regulation of DDR in ischemic AKI remain elusive. In this study, we demonstrated the induction of phosphorylation of ATM, H2AX, Chk2 and p53 during renal ischemia-reperfusion in mice, suggesting DDR in kidney tissues. DDR was also induced in vitro during the recovery or “reperfusion” of renal proximal tubular cells (RPTCs) after ATP-depletion. DDR in RPTCs was abrogated by supplying glucose to maintain ATP via glycolysis, indicating that the DDR depends on ATP depletion. The DDR was also suppressed by the general caspase inhibitor z-VAD and the overexpression of Bcl-2, supporting a role of apoptosis-associated DNA damage in the DDR. N-acetylcysteine (NAC), an antioxidant, suppressed the phosphorylation of ATM and p53 and, to a less extent, Chk2, but NAC increased the phosphorylation and nuclear foci formation of H2AX. Interestingly, NAC increased apoptosis, which may account for the observed H2AX activation. Ku55933, an ATM inhibitor, blocked ATM phosphorylation and ameliorated the phosphorylation of Chk2 and p53, but it increased H2AX phosphorylation and nuclear foci formation. Ku55933 also increased apoptosis in RPTCs following ATP-depletion. The results suggest that DDR occurs during renal ischemia-reperfusion in vivo and ATP-depletion injury in vitro. The DDR is partially induced by apoptosis and oxidative stress-related DNA damage. ATM, as a sensor in the DDR, may play a cytoprotective role against tubular cell injury and death. PMID:24726884

Carcinogens induce loss of the primary cilium in human renal proximal tubular epithelial cells independently of effects on the cell cycle

PubMed Central

Radford, Robert; Slattery, Craig; Jennings, Paul; Blacque, Oliver; Pfaller, Walter; Gmuender, Hans; Van Delft, Joost; Ryan, Michael P.

2012-01-01

The primary cilium is an immotile sensory and signaling organelle found on the majority of mammalian cell types. Of the multitude of roles that the primary cilium performs, perhaps some of the most important include maintenance of differentiation, quiescence, and cellular polarity. Given that the progression of cancer requires disruption of all of these processes, we have investigated the effects of several carcinogens on the primary cilium of the RPTEC/TERT1 human proximal tubular epithelial cell line. Using both scanning electron microscopy and immunofluorescent labeling of the ciliary markers acetylated tubulin and Arl13b, we confirmed that RPTEC/TERT1 cells express primary cilium upon reaching confluence. Treatment with the carcinogens ochratoxin A (OTA) and potassium bromate (KBrO3) caused a significant reduction in the number of ciliated cells, while exposure to nifedipine, a noncarcinogenic renal toxin, had no effect on primary cilium expression. Flow cytometric analysis of the effects of all three compounds on the cell cycle revealed that only KBrO3 resulted in an increase in the proportion of cells entering the cell cycle. Microarray analysis revealed dysregulation of multiple pathways affecting ciliogenesis and ciliary maintenance following OTA and KBrO3 exposure, which were unaffected by nifedipine exposure. The primary cilium represents a unique physical checkpoint with relevance to carcinogenesis. We have shown that the renal carcinogens OTA and KBrO3 cause significant deciliation in a model of the proximal tubule. With KBrO3, this was followed by reentry into the cell cycle; however, deciliation was not found to be associated with reentry into the cell cycle following OTA exposure. Transcriptomic analysis identified dysregulation of Wnt signaling and ciliary trafficking in response to OTA and KBrO3 exposure. PMID:22262483

VCP-dependent muscle degeneration is linked to defects in a dynamic tubular lysosomal network in vivo

PubMed Central

Johnson, Alyssa E; Shu, Huidy; Hauswirth, Anna G; Tong, Amy; Davis, Graeme W

2015-01-01

Lysosomes are classically viewed as vesicular structures to which cargos are delivered for degradation. Here, we identify a network of dynamic, tubular lysosomes that extends throughout Drosophila muscle, in vivo. Live imaging reveals that autophagosomes merge with tubular lysosomes and that lysosomal membranes undergo extension, retraction, fusion and fission. The dynamics and integrity of this tubular lysosomal network requires VCP, an AAA-ATPase that, when mutated, causes degenerative diseases of muscle, bone and neurons. We show that human VCP rescues the defects caused by loss of Drosophila VCP and overexpression of disease relevant VCP transgenes dismantles tubular lysosomes, linking tubular lysosome dysfunction to human VCP-related diseases. Finally, disruption of tubular lysosomes correlates with impaired autophagosome-lysosome fusion, increased cytoplasmic poly-ubiquitin aggregates, lipofuscin material, damaged mitochondria and impaired muscle function. We propose that VCP sustains sarcoplasmic proteostasis, in part, by controlling the integrity of a dynamic tubular lysosomal network. DOI: http://dx.doi.org/10.7554/eLife.07366.001 PMID:26167652

Extracellular 2′,3′-cAMP-adenosine pathway in proximal tubular, thick ascending limb, and collecting duct epithelial cells

PubMed Central

Gillespie, Delbert G.

2013-01-01

In a previous study, we demonstrated that human proximal tubular epithelial cells obtained from a commercial source metabolized extracellular 2′,3′-cAMP to 2′-AMP and 3′-AMP and extracellular 2′-AMP and 3′-AMP to adenosine (the extracellular 2′,3′-cAMP-adenosine pathway; extracellular 2′,3′-cAMP → 2′-AMP + 3′-AMP → adenosine). The purpose of this study was to investigate the metabolism of extracellular 2′,3′-cAMP in proximal tubular vs. thick ascending limb vs. collecting duct epithelial cells freshly isolated from their corresponding nephron segments obtained from rat kidneys. In epithelial cells from all three nephron segments, 1) extracellular 2′,3′-cAMP was metabolized to 2′-AMP and 3′-AMP, with 2′-AMP > 3′-AMP, 2) the metabolism of extracellular 2′,3′-cAMP to 2′-AMP and 3′-AMP was not inhibited by either 3-isobutyl-1-methylxanthine (phosphodiesterase inhibitor) or 1,3-dipropyl-8-p-sulfophenylxanthine (ecto-phosphodiesterase inhibitor), 3) extracellular 2′,3′-cAMP increased extracellular adenosine levels, 4) 3′-AMP and 2′-AMP were metabolized to adenosine with an efficiency similar to that of 5′-AMP, and 5) the metabolism of 5′-AMP, 3′-AMP, and 2′-AMP was not inhibited by α,β-methylene-adenosine-5′-diphosphate (CD73 inhibitor). These results support the conclusion that renal epithelial cells all along the nephron can metabolize extracellular 2′,3′-cAMP to 2′-AMP and 3′-AMP and can efficiently metabolize extracellular 2′-AMP and 3′-AMP to adenosine and that the metabolic enzymes involved are not the classical phosphodiesterases nor ecto-5′-nucleotidase (CD73). Because 2′,3′-cAMP is released by injury and because previous studies demonstrate that the extracellular 2′,3′-cAMP-adenosine pathway stimulates epithelial cell proliferation via adenosine A2B receptors, the present results suggest that the extracellular 2′,3′-cAMP-adenosine pathway may help restore epithelial cells along the nephron following kidney injury. PMID:23077101

Effects of cardiac glycosides on sodium pump expression and function in LLC-PK1 and MDCK cells.

PubMed

Liu, Jiang; Periyasamy, Sankaridrug M; Gunning, William; Fedorova, Olga V; Bagrov, Alexei Y; Malhotra, Deepak; Xie, Zijian; Shapiro, Joseph I

2002-12-01

The decreases in proximal tubule sodium reabsorption seen with chronic renal failure and volume expansion have been ascribed to circulating digitalis-like substances (DLS). However, the circulating concentrations of DLS do not acutely inhibit the sodium pump to a degree consistent with the observed changes in proximal tubule sodium reabsorption. We examined how cell lines that simulated proximal (LLC-PK1) and distal tubule (MDCK) cells responded to acute (30 min) and long-term (up to 12 hours) Na+,K+-ATPase inhibition with DLS. In LLC-PK1, but not MDCK cells, low concentrations of ouabain decreased 86Rb uptake profoundly in a time and dose dependent manner. In LLC-PK1 cells grown to confluence, transcellular 22Na flux was markedly reduced in concert with the decreases in 86Rb uptake. Similar findings were observed with marinobufagenin (MBG) and deproteinated extract of serum derived from patients with chronic renal failure. However, inhibition of the Na+,K+-ATPase with low extracellular potassium concentrations did not produce any of these effects. Western and Northern blots detected no change in alpha1 Na+,K+-ATPase protein and message RNA, respectively, in LLC-PK1 cells treated with ouabain for 12 hours. However, the decrease in enzymatic activity of Na+,K+-ATPase of these cells was comparable to observed decreases in 86Rb uptake. Differential centrifugation as well as biotinylation experiments demonstrated a shift of the Na+,K+-ATPase from the plasmalemma with prolonged ouabain treatment. The results show that binding of cardiac glycosides by proximal (but not distal) tubular cells results in internalization of Na+,K+-ATPase with the net effect to amplify inhibition of the Na+,K+-ATPase. As the circulating concentrations of DLS increase with chronic renal failure and volume expansion, we suggest that this phenomenon explains some of the decreased sodium reabsorption by the proximal tubule seen in these conditions.

DIAGNOSIS AND TREATMENT OF A UNILATERAL RENAL CYSTADENOMA IN AN AFRICAN LION (PANTHERA LEO).

PubMed

Eustace, Ronan; Rubin, Jacob; Thompson, Kimberly A; Snowdon, Kyle; Sikarskie, James G; Monahan, Colleen; Smedley, Rebecca C

2017-09-01

A renal tubular cystadenoma was diagnosed in a 14-yr-old male African lion (Panthera leo). During a routine health evaluation, a left renal mass was identified via physical examination, radiographs, and abdominal ultrasonography. The mass was 30 × 15 cm in size and had a thin capsule with central hypoechoic fluid, suggestive of a perirenal cyst. An exploratory celiotomy with partial nephrectomy was performed without complications. Histologically, the tumor was characterized by a thick fibrous capsule surrounding multiple, variable-sized cysts that markedly compressed the adjacent fibrotic and atrophied renal cortex. Immunohistochemical labeling for Aquaporin-1 and Tamm-Horsfall protein was consistent with a renal tubular cystadenoma of proximal tubule origin. Renal cystadenomas are an uncommon benign epithelial neoplasm. There are only two documented case reports in domestic cats. This report represents the first documentation, to the authors' knowledge, of a renal cystadenoma in a lion.

Renal effects of continuous negative pressure breathing

NASA Technical Reports Server (NTRS)

Kinney, M. J.; Discala, V. A.

1975-01-01

Continuous negative pressure breathing (CNPB) was utilized to simulate the thoracic vascular distension of zero g or space, in 11 anesthetized rats. The animals underwent renal clearance and micropuncture renal nephron studies before, during, and after CNPB. Rats were pretreated with a high salt diet and I-M desoxycorticosterone (DOCA) in excess. None of these rats diuresed with CNPB. In contrast 5 of the 7 remaining rats increased the fraction of the filtered sodium excreted (C sub Na/GFR, p .05) and their urinary flow rate (V, p .05). Potassium excretion increased (U sub k V, p .05). End proximal tubular fluid specimen's TF/P inulin ratios were unchanged. Whole kidney and single nephron glomerular filtration rates fell 10%. CNPB, a mechanism for atrial distension, appears to cause, in rats, a decrease in distal tubular sodium, water and potassium reabsorption. Exogenous mineral-corticoid prevents the diuresis, saluresis, and kaluresis.

Effects of PEG-PLA-nano Artificial Cells Containing Hemoglobin on Kidney Function and Renal Histology in Rats

PubMed Central

Liu, Zun Chang; Chang, Thomas M.S.

2012-01-01

This study is to investigate the long-term effects of PEG-PLA nano artificial cells containing hemoglobin (NanoRBC) on renal function and renal histology after 1/3 blood volume top loading in rats. The experimental rats received one of the following infusions: NanoRBC in Ringer lactate, Ringer lactate, stroma-free hemoglobin (SFHB), polyhemoglobin (PolyHb), autologous rat whole blood (rat RBC). Blood samples were taken before infusions and on days 1, 7 and 21 after infusions for biochemistry analysis. Rats were sacrificed on day 21 after infusions and kidneys were excised for histology examination. Infusion of SFHB induced significant decrease in renal function damage evidenced by elevated serum urea, creatinine and uric acid throughout the 21 days. Kidney histology in SFHb infusion group revealed focal tubular necrosis and intraluminal cellular debris in the proximal tubules, whereas the glomeruli were not observed damaged. In all the other groups, NanoRBC, PolyHb, Ringer lactate and rat RBC, there were no abnormalities in renal biochemistry or histology. In conclusion, injection of NanoRBC did not have adverse effects on renal function nor renal histology. PMID:18979292

Metabolism, Mass Spectral Analysis and Mode of Action of Trichothecene Mycotoxins

DTIC Science & Technology

1988-10-12

tissue, as well as depletion and mild necrosis of thymic lymphoid tissue. Two rats showed mild, acute necrosis of proximal renal tubular epithelium...toxicity in pigs. Res. in Vet. Sci. 31:131. Weaver GA, Hurt.z HJ, Mirocha CU, Bates FY, Behrens JC, Robison TS, and Swanson SP (1980) The failure of purified...by Professor Abraham Joffe. The problem was called alimentary toxic aleukia which affected (according to the chronicles ) thousands of people eating

Interplay between autophagy and apoptosis in lead(II)-induced cytotoxicity of primary rat proximal tubular cells.

PubMed

Chu, Bing-Xin; Fan, Rui-Feng; Lin, Shu-Qian; Yang, Du-Bao; Wang, Zhen-Yong; Wang, Lin

2018-05-01

Autophagy and apoptosis are two different biological processes that determine cell fates. We previously reported that autophagy inhibition and apoptosis induction are involved in lead(II)-induced cytotoxicity in primary rat proximal tubular (rPT) cells, but the interplay between them remains to be elucidated. Firstly, data showed that lead(II)-induced elevation of LC3-II protein levels can be significantly modulated by 3-methyladenine or rapamycin; moreover, protein levels of Autophagy-related protein 5 (Atg5) and Beclin-1 were markedly up-regulated by lead(II) treatment, demonstrating that lead(II) could promote the autophagosomes formation in rPT cells. Next, we applied three pharmacological agents and genetic method targeting the early stage of autophagy to validate that enhancement of autophagosomes formation can inhibit lead(II)-induced apoptotic cell death in rPT cells. Simultaneously, lead(II) inhibited the autophagic degradation of rPT cells, while the addition of autophagic degradation inhibitor bafilomycin A1 aggravated lead(II)-induced apoptotic death in rPT cells. Collectively, this study provided us a good model to know about the dynamic process of lead(II)-induced autophagy in rPT cells, and the interplay between autophagy and apoptosis highlights a new sight into the mechanism of lead(II)-induced nephrotoxicity. Copyright © 2018. Published by Elsevier Inc.

Expression of Renal Aquaporins in Aristolochic Acid I and Aristolactam I-Induced Nephrotoxicity.

PubMed

Li, Ji; Zhang, Liang; Jiang, ZhenZhou; He, XiuQin; Zhang, LuYong; Xu, Ming

2016-01-01

Exposure to aristolochic acid (AA) can cause AA nephropathy, which is characterized by extensive proximal tubular damage and polyuria. To test the hypothesis that polyuria might be induced by altered regulation of aquaporins (AQPs) in the kidney, different doses of AA-I or aristolactam I (AL-I) were administered intraperitoneally to Sprague-Dawley rats, and urine, blood, and kidney samples were analyzed. In addition, AQP1, AQP2, AQP4 and AQP6 expression in the kidney were determined. The results showed dose-dependent proximal tubular damage and polyuria in the AA-I- and AL-I-treated groups, and the nephrotoxicity of AL-I was higher than that of AA-I. The expression of renal AQP1, AQP2 and AQP4, but not AQP6 were significantly inhibited by AA-I and AL-I. Comparison of the inhibition potencies of AA-I and AL-I showed that AL-I was a stronger inhibitor of AQP1 expression than AA-I, while there was no difference in their effects on AQP2 and AQP4. These results suggested that AA induced renal damage and polyuria were associated with a specific decrease in the expression of renal AQP1 AQP2 and AQP4, and AL-I showed higher nephrotoxicity than AA-I, which might be attributable to the differences in their inhibition of AQP1. © 2016 S. Karger AG, Basel.

l-Citrulline Protects from Kidney Damage in Type 1 Diabetic Mice

PubMed Central

Romero, Maritza J.; Yao, Lin; Sridhar, Supriya; Bhatta, Anil; Dou, Huijuan; Ramesh, Ganesan; Brands, Michael W.; Pollock, David M.; Caldwell, Ruth B.; Cederbaum, Stephen D.; Head, C. Alvin; Bagi, Zsolt; Lucas, Rudolf; Caldwell, Robert W.

2013-01-01

Rationale: Diabetic nephropathy (DN) is a major cause of end-stage renal disease, associated with endothelial dysfunction. Chronic supplementation of l-arginine (l-arg), the substrate for endothelial nitric oxide synthase (eNOS), failed to improve vascular function. l-Citrulline (l-cit) supplementation not only increases l-arg synthesis, but also inhibits cytosolic arginase I, a competitor of eNOS for the use of l-arg, in the vasculature. Aims: To investigate whether l-cit treatment reduces DN in streptozotocin (STZ)-induced type 1 diabetes (T1D) in mice and rats and to study its effects on arginase II (ArgII) function, the main renal isoform. Methods: STZ-C57BL6 mice received l-cit or vehicle supplemented in the drinking water. For comparative analysis, diabetic ArgII knock out mice and l-cit-treated STZ-rats were evaluated. Results: l-Citrulline exerted protective effects in kidneys of STZ-rats, and markedly reduced urinary albumin excretion, tubulo-interstitial fibrosis, and kidney hypertrophy, observed in untreated diabetic mice. Intriguingly, l-cit treatment was accompanied by a sustained elevation of tubular ArgII at 16 weeks and significantly enhanced plasma levels of the anti-inflammatory cytokine IL-10. Diabetic ArgII knock out mice showed greater blood urea nitrogen levels, hypertrophy, and dilated tubules than diabetic wild type (WT) mice. Despite a marked reduction in collagen deposition in ArgII knock out mice, their albuminuria was not significantly different from diabetic WT animals. l-Cit also restored nitric oxide/reactive oxygen species balance and barrier function in high glucose-treated monolayers of human glomerular endothelial cells. Moreover, l-cit also has the ability to establish an anti-inflammatory profile, characterized by increased IL-10 and reduced IL-1β and IL-12(p70) generation in the human proximal tubular cells. Conclusion: l-Citrulline supplementation established an anti-inflammatory profile and significantly preserved the nephron function during T1D. PMID:24400007

Proximal Tubular Secretion of Creatinine by Organic Cation Transporter OCT2 in Cancer Patients

PubMed Central

Ciarimboli, Giuliano; Lancaster, Cynthia S.; Schlatter, Eberhard; Franke, Ryan M.; Sprowl, Jason A.; Pavenstädt, Hermann; Massmann, Vivian; Guckel, Denise; Mathijssen, Ron H. J.; Yang, Wenjian; Pui, Ching-Hon; Relling, Mary V.; Herrmann, Edwin; Sparreboom, Alex

2012-01-01

Purpose Knowledge of transporters responsible for the renal secretion of creatinine is key to a proper interpretation of serum creatinine and/or creatinine clearance as markers of renal function in cancer patients receiving chemotherapeutic agents. Experimental Design Creatinine transport was studied in transfected HEK293 cells in vitro and in wildtype mice and age-matched organic cation transporter 1 and 2-deficient [Oct1/2(−/−)] mice ex vivo and in vivo. Clinical pharmacogenetic and transport inhibition studies were done in two separate cohorts of cancer patients. Results Compared to wildtype mice, creatinine clearance was significantly impaired in Oct1/2(−/−) mice. Furthermore, creatinine inhibited organic cation transport in freshly-isolated proximal tubules from wild-type mice and humans, but not in those from Oct1/2(−/−) mice. In a genetic-association analysis (n=590), several polymorphisms around the OCT2/SLC22A2 gene locus, including rs2504954 (P=0.000873), were significantly associated with age-adjusted creatinine levels. Furthermore, in cancer patients (n=68), the OCT2 substrate cisplatin caused an acute elevation of serum creatinine (P=0.0083), consistent with inhibition of an elimination pathway. Conclusions Collectively, this study shows that OCT2 plays a decisive role in the renal secretion of creatinine. This process can be inhibited by OCT2 substrates, which impair the usefulness of creatinine as a marker of renal function. PMID:22223530

METHOD AND APPARATUS FOR FABRICATING TUBULAR UNITS

DOEpatents

Haldeman, G.W.

1959-02-24

A method and apparatus are described for fabricating tubular assemblies such as clad fuel elements for nuclear reactors. According to this method, a plurality of relatively short cylindrical slug-shaped members are inserted in an outer protective tubular jacket, and the assembly is passed through a reducing die to draw the outer tubular member into tight contact with the slug members, the slugs being automatically spaced with respect to each other and helium being inserted during the drawing operation to fill the spaces. The apparatus includes a pusher rod which functions to space the slugelements equidistantly by pushing on them in the direction of drawing but traveling at a slower rate than that of the tubular member.

A critical synopsis: Continuous growth of proximal tubular kidney epithelial cells in hormone-supplemented serum-free medium

NASA Technical Reports Server (NTRS)

Chuman, L. M.; FINE; COHEN; Saier, M. H.

1985-01-01

The kidney forms urine and reabsorbs electrolytes and water. Kidney cell lines and hormone supplemented serum free medium were used for growth. The hormones were insulin, transferrin, vasopressin, cholesterol, prostaglandins, hydrocortisone, and triidothyronine. Epithelial cell lines are polar and form hemicysts. The Madin-Darby canine kidney(MDCK) cell line used is distal tubulelike. LLC-PK sub 1 cells are derived from pig kidneys and have the properties of different kidney segments. The LLC-PK sub 1 cells with proximal tubule properties were maintained in hormone-supplemented serum free medium. Seven factors (the aforementioned homrones and selenium) were needed for growth. Hormone-defined medium supported LLC-PK sub 1 cell growth, allowed transport (as seen by hemicyst formation), and influenced cell morphology. Vasopressin (used for growth and morphology) could be partially replaced by isobutylmethylxanthine or dibutyryl cAMP. The defined medium was used to isolate rabbit proximal tubule kidney epithelial cells free of fibroblasts.

Phosphoproteomic analysis of AT1 receptor-mediated signaling responses in proximal tubules of angiotensin II-induced hypertensive rats.

PubMed

Li, Xiao C; Zhuo, Jia L

2011-09-01

The signaling mechanisms underlying the effects of angiotensin II in proximal tubules of the kidney are not completely understood. Here we measured signal protein phosphorylation in isolated proximal tubules using pathway-specific proteomic analysis in rats continuously infused with pressor or non-pressor doses of angiotensin II over a 2-week period. Of the 38 phosphoproteins profiled, 14 were significantly altered by the pressor dose. This included increased phosphorylation of the protein kinase C isoenzymes, PKCα and PKCβII, and the glycogen synthase kinases, GSK3α and GSK3β. Phosphorylation of the cAMP-response element binding protein 1 and PKCδ were decreased, whereas PKCɛ remained unchanged. By contrast, the phosphorylation of only seven proteins was altered by the non-pressor dose, which increased that of PKCα, PKCδ, and GSKα. Phosphorylation of MAP kinases, ERK1/2, was not increased in proximal tubules in vivo by the pressor dose, but was in proximal tubule cells in vitro. Infusion of the pressor dose decreased, whereas the non-pressor dose of angiotensin II increased the phosphorylation of the sodium and hydrogen exchanger 3 (NHE-3) in membrane fractions of proximal tubules. Losartan largely blocked the signaling responses induced by the pressor dose. Thus, PKCα and PKCβII, GSK3α and GSK3β, and cAMP-dependent signaling pathways may have important roles in regulating proximal tubular sodium and fluid transport in Ang II-induced hypertensive rats.

Metal accumulation and nephron heterogeneity in mercuric chloride-induced acute renal failure.

PubMed

Wilks, M F; Gregg, N J; Bach, P H

1994-01-01

The present study was designed to assess the effects of mercury on glomerular integrity during the early phase of acute renal failure. The silver amplification method showed distribution of mercury in midcortical and juxtamedullary glomeruli and on the brush border of the S2 segment of the proximal tubule 15 min after treatment. At 30 min, there was a decrease in glomerular staining and increased mercury in the proximal tubule. After 3 hr, mercury was no longer detectable in glomeruli but was widespread in the lumen of the proximal tubule. By 24 hr, mercury was prominent in all proximal tubular segments throughout the cortex. The presence of mercury in glomeruli was not related to hemodynamic changes, as there was no evidence for blood redistribution toward juxtamedullary glomeruli as assessed by the filling of the microvascular system with Monastral Blue B. The reduced activity of horseradish peroxidase (administered i.v. 90 sec and 10 min before sacrifice) in juxtamedullary glomeruli 30 min after mercury administration suggests a decreased uptake of horseradish peroxidase or an increased glomerular protein filtration. These data support glomerular filtration as the predominant excretory route for mercury, highlight the marked nephron heterogeneity in the distribution of this metal, and show that impairment of glomerular integrity occurs before necrosis of the proximal tubules and acute renal failure.

Dose-related nephrotoxicity of carboplatin in children

PubMed Central

English, M W; Skinner, R; Pearson, A D J; Price, L; Wyllie, R; Craft, A W

1999-01-01

This study investigated changes and the time course of these changes in renal function in children following treatment with carboplatin, and identified risk factors for nephrotoxicity. Glomerular and proximal renal tubular function were investigated before and up to 2 years after treatment in 23 children who received carboplatin. The main findings were reduced glomerular filtration rate (GFR), and increased renal tubular loss of magnesium, manifested by a low serum magnesium (S Mg). The mean fall in GFR was 22 ml min−1 1.73 m−2 (P = 0.012), and in S Mg it was 0.17 mmol l−1 (P = 0.0077). No patient had a clinically important reduction in GFR, and only one patient had symptomatic hypomagnesaemia. GFR and S Mg did not change over time after completion of treatment. Cumulative dose (CD) of carboplatin was inversely related to mean S Mg at the end of treatment (P = 0.031), and directly related to the fall in S Mg (P < 0.001). Calculated cumulative area under the plasma concentration versus time curve (AUC) of carboplatin was inversely related to S Mg after treatment (P = 0.004). Dose intensity (DI) of carboplatin was not shown to be related to S Mg following treatment. CD, AUC and DI of carboplatin were not related to GFR, nor change in GFR, after treatment. High CDs of carboplatin may be associated with evidence of renal damage qualitatively similar to but less severe than that caused by cisplatin. GFR and SMg should be carefully monitored when high CDs of carboplatin are used, or if carboplatin is combined with other nephrotoxic chemotherapy. © 1999 Cancer Research Campaign PMID:10496362

Partitioning-Defective 1a/b Depletion Impairs Glomerular and Proximal Tubule Development.

PubMed

Akchurin, Oleh; Du, Zhongfang; Ramkellawan, Nadira; Dalal, Vidhi; Han, Seung Hyeok; Pullman, James; Müsch, Anne; Susztak, Katalin; Reidy, Kimberly J

2016-12-01

The kidney is a highly polarized epithelial organ that develops from undifferentiated mesenchyme, although the mechanisms that regulate the development of renal epithelial polarity are incompletely understood. Partitioning-defective 1 (Par1) proteins have been implicated in cell polarity and epithelial morphogenesis; however, the role of these proteins in the developing kidney has not been established. Therefore, we studied the contribution of Par1a/b to renal epithelial development. We examined the renal phenotype of newborn compound mutant mice carrying only one allele of Par1a or Par1b. Loss of three out of four Par1a/b alleles resulted in severe renal hypoplasia, associated with impaired ureteric bud branching. Compared with kidneys of newborn control littermates, kidneys of newborn mutant mice exhibited dilated proximal tubules and immature glomeruli, and the renal proximal tubular epithelia lacked proper localization of adhesion complexes. Furthermore, Par1a/b mutants expressed low levels of renal Notch ligand Jag1, activated Notch2, and Notch effecter Hes1. Together, these data demonstrate that Par1a/b has a key role in glomerular and proximal tubule development, likely via modulation of Notch signaling. Copyright © 2016 by the American Society of Nephrology.

Quantitative and semi-quantitative histopathological examination of renal biopsies in healthy individuals, and associations with kidney function.

PubMed

Bar, Yael; Barregard, Lars; Sallsten, Gerd; Wallin, Maria; Mölne, Johan

2016-05-01

This study assesed the prevalence of histopathological changes in renal biopsies from healthy individuals, and the association with age, sex and smoking. Donor biopsies from 109 subjects were obtained from living kidney donors, and blood and urine samples were collected together with medical history. All biopsies were scored according to the Banff '97 classification with some modifications. The parameters included in this study were tubular atrophy, interstitial fibrosis, glomerulosclerosis, arteriosclerosis, arteriolohyalinosis and a sclerosis score. An alternative scoring system for tubular atrophy was examined (using ≤5% rather than <1% as a cut-off for grade 0). Glomerular filtration rate was measured in most cases as chromium ethylenediaminetetra-acetic acid (Cr-EDTA) clearance. Age was a significant predictor for tubular atrophy, fibrosis and sclerosis. Pack-years of smoking increased the risk of tubular atrophy, fibrosis and arteriolohyalinosis. The alternative scoring of tubular atrophy showed a stronger association with smoking, but a weaker association with age, compared with the original one. Limited histopathological changes are common in healthy kidney donors around 50 years of age with normal kidney function. We propose that a cut-off of ≤5% yields a better definition of grade 0 tubular atrophy compared with the established cut-off of >0%. © 2016 APMIS. Published by John Wiley & Sons Ltd.

Mutations in GFPT1-related congenital myasthenic syndromes are associated with synaptic morphological defects and underlie a tubular aggregate myopathy with synaptopathy.

PubMed

Bauché, Stéphanie; Vellieux, Geoffroy; Sternberg, Damien; Fontenille, Marie-Joséphine; De Bruyckere, Elodie; Davoine, Claire-Sophie; Brochier, Guy; Messéant, Julien; Wolf, Lucie; Fardeau, Michel; Lacène, Emmanuelle; Romero, Norma; Koenig, Jeanine; Fournier, Emmanuel; Hantaï, Daniel; Streichenberger, Nathalie; Manel, Veronique; Lacour, Arnaud; Nadaj-Pakleza, Aleksandra; Sukno, Sylvie; Bouhour, Françoise; Laforêt, Pascal; Fontaine, Bertrand; Strochlic, Laure; Eymard, Bruno; Chevessier, Frédéric; Stojkovic, Tanya; Nicole, Sophie

2017-08-01

Mutations in GFPT1 (glutamine-fructose-6-phosphate transaminase 1), a gene encoding an enzyme involved in glycosylation of ubiquitous proteins, cause a limb-girdle congenital myasthenic syndrome (LG-CMS) with tubular aggregates (TAs) characterized predominantly by affection of the proximal skeletal muscles and presence of highly organized and remodeled sarcoplasmic tubules in patients' muscle biopsies. We report here the first long-term clinical follow-up of 11 French individuals suffering from LG-CMS with TAs due to GFPT1 mutations, of which nine are new. Our retrospective clinical evaluation stresses an evolution toward a myopathic weakness that occurs concomitantly to ineffectiveness of usual CMS treatments. Analysis of neuromuscular biopsies from three unrelated individuals demonstrates that the maintenance of neuromuscular junctions (NMJs) is dramatically impaired with loss of post-synaptic junctional folds and evidence of denervation-reinnervation processes affecting the three main NMJ components. Moreover, molecular analyses of the human muscle biopsies confirm glycosylation defects of proteins with reduced O-glycosylation and show reduced sialylation of transmembrane proteins in extra-junctional area. Altogether, these results pave the way for understanding the etiology of this rare neuromuscular disorder that may be considered as a "tubular aggregates myopathy with synaptopathy".

A relationship between proteinuria and acute tubulointerstitial disease in rats with experimental nephrotic syndrome

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eddy, A.A.; McCulloch, L.; Liu, E.

1991-05-01

The relationship between tubulointerstitial nephritis and proteinuria was characterized in experimental nephrosis in rats. In one group, proteinuria induced by aminonucleoside of puromycin (PAN) was reduced by using an 8% protein diet and adding the angiotensin I-converting enzyme (ACE) inhibitor enalapril to the drinking water. Two control groups were injected with saline and PAN, respectively, and fed a 27% protein diet. The first group had significantly reduced albuminuria and a definite attenuation of tubular cell injury. There was a strong positive correlation between the number of interstitial macrophages and albuminuria. The beneficial effect was reproduced by dietary-protein restriction alone, whereasmore » ACE inhibition alone had an insignificant effect on the degree of proteinuria. Depletion of circulating T lymphocytes in one group of nephrotic rats eliminated interstitial lymphocytes but did not affect interstitial macrophage influx. Inhibition of the in situ proliferation of resident interstitial macrophages by unilateral kidney irradiation failed to change the intensity of the macrophage infiltration. Treatment of rats with sodium maleate produced proximal tubular cell toxicity but interstitial inflammation did not develop, suggesting that the latter is not a nonspecific response to tubular injury. These studies demonstrate a strong relationship between tubulointerstitial nephritis and the severity of proteinuria in experimental nephrosis.« less

Pharmacological inhibition of NADPH oxidase protects against cisplatin induced nephrotoxicity in mice by two step mechanism.

PubMed

Wang, Yimin; Luo, Xiao; Pan, Hao; Huang, Wei; Wang, Xueping; Wen, Huali; Shen, Kezhen; Jin, Baiye

2015-09-01

Cisplatin induced nephrotoxicity is primarily caused by ROS (Reactive Oxygen Species) induced proximal tubular cell death. NADPH oxidase is major source of ROS production by cisplatin. Here, we reported that pharmacological inhibition of NADPH oxidase by acetovanillone (obtained from medicinal herb Picrorhiza kurroa) led to reduced cisplatin nephrotoxicity in mice. In this study we used various molecular biology and biochemistry methods a clinically relevant model of nephropathy, induced by an important chemotherapeutic drug cisplatin. Cisplatin-induced nephrotoxicity was evident by histological damage from loss of the tubular structure. The damage was also marked by the increase in blood urea nitrogen, creatinine, protein nitration as well as cell death markers such as caspase 3/7 activity and DNA fragmentation. Tubular cell death by cisplatin led to pro-inflammatory response by production of TNFα and IL1β followed by leukocyte/neutrophil infiltration which resulted in new wave of ROS involving more NADPH oxidases. Cisplatin-induced markers of kidney damage such as oxidative stress, cell death, inflammatory cytokine production and nephrotoxicity were attenuated by acetovanillone. In addition to that, acetovanillone enhanced cancer cell killing efficacy of cisplatin. Thus, pharmacological inhibition of NADPH oxidase can be protective for cisplatin-induced nephrotoxicity in mice. Copyright © 2015. Published by Elsevier Ltd.

Clinical characteristics and predictive factors of subclinical diabetic nephropathy.

PubMed

Zhang, Y; Yang, J; Zheng, M; Wang, Y; Ren, H; Xu, Y; Yang, Y; Cheng, J; Han, F; Yang, X; Chen, L; Shan, C; Chang, B

2015-02-01

To investigate the clinical characteristics and predictive factors of subclinical diabetic nephropathy in type 2 diabetes patients. A total of 298 type 2 diabetes patients were divided into 3 groups based on 24-h urinary microalbumin and estimated glomerular filtration rate: patients with normal albuminuria and glomerular filtration rate (NC), patients with normoalbuminuria and glomerular hyperfiltration (SDN) and patients with microalbuminuria (EDN). The renal size, tubular injury markers and ambulatory blood pressure were analyzed. Renal size increased in the SDN and EDN groups compared to the NC group (P<0.05), while renal length in the SDN group was greater than the EDN group (P<0.05). Patients in the SDN and EDN groups had higher level of urine retinol binding protein and N-acetyl-β-D-glucosaminidase and most of them developed proximal tubular dysfunction. The SDN group had higher 24-h mean and nocturnal diastolic blood pressure than the NC group (P<0.05), while the EDN group had higher systolic blood pressure and pulse pressure than the SDN group (P<0.01). More patients developed abnormal blood pressure rhythm in the SDN and EDN groups. The likelihood of a decrease in nocturnal systolic blood pressure was lower as the microalbuminuria increased. Increased renal size, more abnormal tubular injury markers and higher 24-h mean and nocturnal blood pressure were all risk factors of subclinical diabetic nephropathy. Patients with subclinical diabetic nephropathy had increased renal size, abnormal tubular injury markers, high blood pressure and abnormal circadian rhythm. © Georg Thieme Verlag KG Stuttgart · New York.

Molecular mechanisms of acid-base sensing by the kidney.

PubMed

Brown, Dennis; Wagner, Carsten A

2012-05-01

A major function of the kidney is to collaborate with the respiratory system to maintain systemic acid-base status within limits compatible with normal cell and organ function. It achieves this by regulating the excretion and recovery of bicarbonate (mainly in the proximal tubule) and the secretion of buffered protons (mainly in the distal tubule and collecting duct). How proximal tubular cells and distal professional proton transporting (intercalated) cells sense and respond to changes in pH, bicarbonate, and CO(2) status is a question that has intrigued many generations of renal physiologists. Over the past few years, however, some candidate molecular pH sensors have been identified, including acid/alkali-sensing receptors (GPR4, InsR-RR), kinases (Pyk2, ErbB1/2), pH-sensitive ion channels (ASICs, TASK, ROMK), and the bicarbonate-stimulated adenylyl cyclase (sAC). Some acid-sensing mechanisms in other tissues, such as CAII-PDK2L1 in taste buds, might also have similar roles to play in the kidney. Finally, the function of a variety of additional membrane channels and transporters is altered by pH variations both within and outside the cell, and the expression of several metabolic enzymes are altered by acid-base status in parts of the nephron. Thus, it is possible that a master pH sensor will never be identified. Rather, the kidney seems equipped with a battery of molecules that scan the epithelial cell environment to mount a coordinated physiologic response that maintains acid-base homeostasis. This review collates current knowledge on renal acid-base sensing in the context of a whole organ sensing and response process.

Impact of thoracic surgery on esophageal motor function-Evaluation by high resolution manometry.

PubMed

Wäsche, Anja; Kandulski, Arne; Malfertheiner, Peter; Riedel, Sandra; Zardo, Patrick; Hachenberg, Thomas; Schreiber, Jens

2017-06-01

Alteration of esophageal function is a potential risk factor for postoperative complications in thoracic surgery. This prospective study investigates esophageal motility and function during and after thoracic procedures via high resolution manometry (HRM) and impedance technology with spatiotemporal representation of pressure data. Twelve consecutive patients eligible for elective thoracic surgery underwent preoperative and postoperative (48 hours and 7 days) esophageal HRM. Swallowing acts were carried out with 5 mL of water, 10 mL of water and 1 cm 3 bread in physiological posture to evaluate distal contraction integral (DCI). Length and location of contractile integrity breaks were measured by investigators blinded to the form of surgical intervention. The impact of surgical procedures on esophageal motility was quantified according to current Chicago Classification (CC) criteria. Pre-, intra- and postoperative 24-hour multi-channel impedance pH-metry (MII-pH) was performed to further analyze gastroesophageal reflux patterns. All patients were investigated 48 hours prior to and 7 days after thoracic procedures, with a total of n=675 swallowing acts being included in our study. Increased motility patterns of the tubular esophagus occurred temporally 48 hours postoperatively. DCI 48 hours after surgery increased significantly (5 mL, P=0.049; solid, P=0.014) and returned to baseline values after seven days (5 mL, P=0.039; solid, P=0.039). Break length was significantly reduced 48 hours postoperatively, especially in the proximal esophageal segment (transition zone). Follow-up measurements after another week were comparable to preoperative baseline findings. The perioperative MII-pH measurement showed numerous artifacts caused by intubation and ventilation during surgery also with increasing short and frequent acidic reflux episodes. Thoracic procedures cause a transient modulation of esophageal peristalsis with postoperative increased contractility of the tubular esophagus, presumably without affecting intraesophageal reflex arcs. Although limited by the number of patients, we can conclude on our data that postoperative esophageal hypomotility is unlikely to promote secondary pulmonary complications.

BSC-1 growth inhibitor transforms a mitogenic stimulus into a hypertrophic stimulus for renal proximal tubular cells: relationship to Na/sup +//H/sup +/ antiport activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fine, L.G.; Holley, R.W.; Nasri, H.

Renal hypertrophy is characterized by an increase in cell size and protein content with minimal hyperplasia. The mechanisms of control of this pattern of cell growth have not been determined. The present studies examined whether the growth inhibitor elaborated by BSC-1 kidney epilethal cells (GI), which has nearly identical biological properties to transforming growth factor ..beta.. (TGF-..beta..), could transform a mitogenic stimulus into a hypertrophic stimulus for rabbit renal proximal tubular cells in primary culture. Insulin plus hydrocortisone increased the amount of protein per cell, cell volume, and (/sup 3/H)thymidine incorporation at 24 and 48 hr in these cells. Whenmore » added together with insulin plus hydrocortisone, GI/TGF-..beta.. inhibited the stimulatory effect of these mitogens on (/sup 3/H)thymidine incorporation but did not block the increase in protein per cell and cell volume - i.e., the cells underwent hypertrophy. The fact that this pattern persisted for 48 hr indicated that GI/TGF-..beta.. exerted a prolonged inhibitory effect on mitogenic-stimulated DNA synthesis rather than delaying its onset. Amiloride-sensitive Na/sup +/ uptake using /sup 22/Na/sup +/ as a tracer, correlated with protein per cell and cell volume rather than with DNA synthesis. These studies indicate that the control of cell size may be regulated by autocrine mechanisms mediated by the elaboration of growth inhibitory factors that alter the pattern of the growth response to mitogens.« less

A common variant of MAF/c-MAF, transcriptional factor gene in the kidney, is associated with gout susceptibility.

PubMed

Higashino, Toshihide; Matsuo, Hirotaka; Okada, Yukinori; Nakashima, Hiroshi; Shimizu, Seiko; Sakiyama, Masayuki; Tadokoro, Shin; Nakayama, Akiyoshi; Kawaguchi, Makoto; Komatsu, Mako; Hishida, Asahi; Nakatochi, Masahiro; Ooyama, Hiroshi; Imaki, Junko; Shinomiya, Nariyoshi

2018-01-01

Gout is a multifactorial disease characterized by acute inflammatory arthritis, and it is caused as a consequence of hyperuricemia. A recent meta-analysis of genome-wide association studies has newly identified the relationship between serum uric acid (SUA) levels and rs889472, a single nucleotide polymorphism of musculoaponeurotic fibrosarcoma oncogene (MAF/c-MAF). However, it remained unclear whether rs889472 is associated with gout susceptibility. In the present study, we investigate the association between c-MAF rs889472 and gout in Japanese male population. We genotyped 625 male patients who were clinically diagnosed as gout and 1221 male control subjects without hyperuricemia or a history of gout by TaqMan method. As a result, the major allele (C), which reportedly increases SUA levels, had a higher frequency in the gout cases (58.8%) than in the controls (55.0%). A logistic regression analysis showed a significant association between rs889472 and gout (p = 0.029, odds ratio = 1.17; 95% confidence interval 1.02-1.34). C-MAF is reported as a pivotal transcriptional factor in the development and differentiation of renal proximal tubular cells. Because urate is mainly regulated in renal proximal tubular cells, c-MAF may have an important role in urate regulation in the kidney and influence not only SUA but also gout susceptibility. Our finding shows that rs889472 of c-MAF is associated with gout susceptibility.

Hypophosphatemic osteomalacia: an unusual clinical presentation of multiple myeloma.

PubMed

Reyskens, M; Sleurs, K; Verresen, L; Janssen, M; van den Bergh, J; van den Berg, J; Geusens, P

2015-07-01

An unusual case of a 75-year-old man is presented who had multiple stress fractures due to adult onset hypophosphatemic osteomalacia, which was the result of Fanconi syndrome, with light chain cast proximal tubulopathy due to multiple myeloma. A 75-year-old man presented with diffuse pain and muscle weakness. He had multiple stress fractures, low serum phosphate, decreased renal tubular reabsorption of phosphate, and normal PTH and FGF23, indicating adult onset hypophosphatemic osteomalacia. Phosphate supplements with calcitriol resulted in clinical recovery and healing of stress fractures. Because of proteinuria, a renal biopsy was performed that revealed Fanconi syndrome with light chain cast proximal tubulopathy and light kappa chains were found in serum and urine. A bone biopsy confirmed the diagnosis of multiple myeloma, and treatment with chemotherapy resulted in cytological and clinical recovery.

Electrochemical forces for chloride transport in the proximal tubules of the rat kidney.

PubMed

Sohtell, M

1978-08-01

The electrochemical forces for chloride transport in the proximal tubule of the rat kidney were studied using micropuncture techniques. Electrical transmembrane potentials were recorded in randomly punctured tubules with Ling-Gerhard electrodes. Chloride activities in the luminal, cellular and interstitial compartments were measured with ion selective micro-electrodes. Electrical potential measurements between cell to interstitium and lumen to interstitium were -72.1 +/- 2.6 mV and +0.5 +/- 1.4 mV (mean +/- S.D.) respectively. The calculated chloride concentrations for lumen, cell and interstitium were 133.0 +/- 10.3 mM, 8.5 +/- 1.0 mM and 99.1 +/- 3.2 mM (mean +/- S.D.) respectively. The net electrochemical forces, qualitatively, offer a passive chloride ion pathway through the tubular wall and a chloride equilibrium over the luminal membrane seems to exist.

NADPH oxidase inhibition reduces tubular sodium transport and improves kidney oxygenation in diabetes.

PubMed

Persson, Patrik; Hansell, Peter; Palm, Fredrik

2012-06-15

Sustained hyperglycemia is associated with increased oxidative stress resulting in decreased intrarenal oxygen tension (Po(2)) due to increased oxygen consumption (Qo(2)). Chronic blockade of the main superoxide radicals producing system, the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, normalizes Qo(2) by isolated proximal tubular cells (PTC) and reduces proteinuria in diabetes. The aim was to investigate the effects of acute NADPH oxidase inhibition on tubular Na(+) transport and kidney Po(2) in vivo. Glomerular filtration rate (GFR), renal blood flow (RBF), filtration fraction (FF), Na(+) excretion, fractional Li(+) excretion, and intrarenal Po(2) was measured in control and streptozotocin-diabetic rats during baseline and after acute NADPH oxidase inhibition using apocynin. The effects on tubular transporters were investigated using freshly isolated PTC. GFR was increased in diabetics compared with controls (2.2 ± 0.3 vs. 1.4 ± 0.1 ml·min(-1)·kidney(-1)). RBF was similar in both groups, resulting in increased FF in diabetics. Po(2) was reduced in cortex and medulla in diabetic kidneys compared with controls (34.4 ± 0.7 vs. 42.5 ± 1.2 mmHg and 15.7 ± 1.2 vs. 25.5 ± 2.3 mmHg, respectively). Na(+) excretion was increased in diabetics compared with controls (24.0 ± 4.7 vs. 9.0 ± 2.0 μm·min(-1)·kidney(-1)). In controls, all parameters were unaffected. However, apocynin increased Na(+) excretion (+112%) and decreased fractional lithium reabsorption (-10%) in diabetics, resulting in improved cortical (+14%) and medullary (+28%) Po(2). Qo(2) was higher in PTC isolated from diabetic rats compared with control. Apocynin, dimethylamiloride, and ouabain reduced Qo(2), but the effects of combining apocynin with either dimethylamiloride or ouabain were not additive. In conclusion, NADPH oxidase inhibition reduces tubular Na(+) transport and improves intrarenal Po(2) in diabetes.

DNA damage response in renal ischemia-reperfusion and ATP-depletion injury of renal tubular cells.

PubMed

Ma, Zhengwei; Wei, Qingqing; Dong, Guie; Huo, Yuqing; Dong, Zheng

2014-07-01

Renal ischemia-reperfusion leads to acute kidney injury (AKI) that is characterized pathologically by tubular damage and cell death, followed by tubular repair, atrophy and interstitial fibrosis. Recent work suggested the possible presence of DNA damage response (DDR) in AKI. However, the evidence is sketchy and the role and regulation of DDR in ischemic AKI remain elusive. In this study, we demonstrated the induction of phosphorylation of ATM, H2AX, Chk2 and p53 during renal ischemia-reperfusion in mice, suggesting DDR in kidney tissues. DDR was also induced in vitro during the recovery or "reperfusion" of renal proximal tubular cells (RPTCs) after ATP depletion. DDR in RPTCs was abrogated by supplying glucose to maintain ATP via glycolysis, indicating that the DDR depends on ATP depletion. The DDR was also suppressed by the general caspase inhibitor z-VAD and the overexpression of Bcl-2, supporting a role of apoptosis-associated DNA damage in the DDR. N-acetylcysteine (NAC), an antioxidant, suppressed the phosphorylation of ATM and p53 and, to a less extent, Chk2, but NAC increased the phosphorylation and nuclear foci formation of H2AX. Interestingly, NAC increased apoptosis, which may account for the observed H2AX activation. Ku55933, an ATM inhibitor, blocked ATM phosphorylation and ameliorated the phosphorylation of Chk2 and p53, but it increased H2AX phosphorylation and nuclear foci formation. Ku55933 also increased apoptosis in RPTCs following ATP depletion. The results suggest that DDR occurs during renal ischemia-reperfusion in vivo and ATP-depletion injury in vitro. The DDR is partially induced by apoptosis and oxidative stress-related DNA damage. ATM, as a sensor in the DDR, may play a cytoprotective role against tubular cell injury and death. Copyright © 2014 Elsevier B.V. All rights reserved.

Tubular Tissues and Organs of Human Body--Challenges in Regenerative Medicine.

PubMed

Góra, Aleksander; Pliszka, Damian; Mukherjee, Shayanti; Ramakrishna, Seeram

2016-01-01

Tissue engineering of tubular organs such as the blood vessel, trachea gastrointestinal tract, urinary tract are of the great interest due to the high amount of surgeries performed annually on those organs. Development in tissue engineering in recent years and promising results, showed need to investigate more complex constructs that need to be designed in special manner. Stent technology remain the most widely used procedure to restore functions of tubular tissues after cancer treatment, or after organ removal due to traumatic accidents. Tubular structures like blood vessels, intestines, and trachea have to work in specific environment at the boundary of the liquids, solids or air and surrounding tissues and ensure suitable separation between them. This brings additional challenges in tissue engineering science in order to construct complete organs by using combinations of various cells along with the support material systems. Here we give a comprehensive review of the tubular structures of the human body, in perspective of the current methods of treatment and progress in regenerative medicine that aims to develop fully functioning organs of tubular shape. Extensive analysis of the available literature has been done focusing on materials and methods of creations of such organs. This work describes the attempts to incorporate growth factors and drugs within the scaffolds to ensure localized drug release and enhance vascularization of the organ by attracting blood vessels to the site of implantation.

Renal cysteine conjugate C-S lyase mediated toxicity of halogenated alkenes in primary cultures of human and rat proximal tubular cells.

PubMed

McGoldrick, Trevor A; Lock, Edward A; Rodilla, Vicente; Hawksworth, Gabrielle M

2003-07-01

Proximal tubular cells from human (HPT) and rat (RPT) kidneys were isolated, grown to confluence and incubated with S-(1,2-dichlorovinyl)- l-cysteine (DCVC), S-(1,2,2-trichlorovinyl)- l-cysteine (TCVC), S-(1,1,2,2-tetrafluoroethyl)- l-cysteine (TFEC) and S-(2-chloro-1,1-difluorethyl)- l-cysteine (CDFEC), the cysteine conjugates of nephrotoxicants. The cultures were exposed to the conjugates for 12, 24 and 48 h and the toxicity determined using the MTT assay. All four conjugates caused dose-dependent toxicity to RPT cells over the range 50-1,000 microM, the order of toxicity being DCVC>TCVC>TFEC=CDFEC. The inclusion of aminooxyacetic acid (AOAA; 250 microM), an inhibitor of pyridoxal phosphate-dependent enzymes such as C-S lyase, afforded protection, indicating that C-S lyase has a role in the bioactivation of these conjugates. In HPT cultures only DCVC caused significant time- and dose-dependent toxicity. Exposure to DCVC (500 microM) for 48 h decreased cell viability to 7% of control cell values, whereas co-incubation of DCVC (500 microM) with AOAA (250 microM) resulted in cell viability of 71%. Human cultures were also exposed to S-(1,2-dichlorovinyl)-glutathione (DCVG). DCVG was toxic to HPT cells, but the onset of toxicity was delayed compared with the corresponding cysteine conjugate. AOAA afforded almost complete protection from DCVG toxicity. Acivicin (250 microM), an inhibitor of gamma-glutamyl transferase (gamma-GT), partially protected against DCVG (500 microM)-induced toxicity at 48 h (5% viability and 53% viability in the absence and presence of acivicin, respectively). These results suggest that DCVG requires processing by gamma-GT prior to bioactivation by C-S lyase in HPT cells. The activity of C-S lyase, using TFEC as a substrate, and glutamine transaminase K (GTK) was measured in rat and human cells with time in culture. C-S lyase activity in RPT and HPT cells decreased to approximately 30% of fresh cell values by the time the cells reached confluence (120 h), whereas the decline in GTK activity was less marked (50% of the fresh cell values at confluence). Rat cells had threefold higher activity than human cells at each time point. This higher activity may partly explain the differences in toxicity between rat and human proximal tubular cells in culture.

Hypophosphataemia: an easy strategy for diagnosis and treatment in HIV patients.

PubMed

Bagnis, Corinne Isnard; Karie, Svetlana; Deray, Gilbert; Essig, Marie

2009-01-01

Because HIV infection has become a chronic disease, it is crucial that metabolic complications secondary to HIV infection or prolonged therapy be diagnosed and managed appropriately over time. Therefore the optimal follow-up becomes complex and time consuming. Our review aimed to provide physicians in charge of HIV-infected patients with key data helping them to diagnose and understand hypophosphataemia in HIV patients. Hypophosphataemia is frequent and sometimes secondary to renal phosphate wasting. It is very rarely a component of a complex proximal tubular disorder, such as Fanconi syndrome. When isolated, hypophosphataemia is easy to rule out and treat. In rare cases, prolonged hypophosphataemia, when related to renal phosphate wasting and tubular dysfunction, might have potential consequences on bone outcome, however, more studies are needed. HIV infection by itself might be a risk factor for bone metabolism abnormalities; antiretroviral drugs might also be involved. Therefore, it seems valuable for patients that the minimal screening should be performed routinely, in order to prevent long-term disabilities.

Renal effects of continuous negative pressure breathing

NASA Technical Reports Server (NTRS)

Kinney, M. J.

1975-01-01

Continuous negative pressure breathing (CNPB) was utilized to simulate the thoracic vascular distension of zero G in 11 anesthetized rats. The animals underwent renal clearance and micropuncture renal nephron studies before, during, and after CNPB. Four rats were pretreated with a high salt diet and I-M desoxycorticosterone (DOCA) in excess. None of these rats diuresed with CNPB. In contrast, five of the seven remaining rats increased the fraction of the filtered sodium excreted and their urinary flow rate. Potassium excretion increased. End proximal tubular fluid specimen's TF/P inulin ratios were unchanged. Whole kidney and single nephron glomerular filtration rates fell 10%. CNPB, a mechanism for atrial distension, appears to cause in the rat a decrease in distal tubular sodium and water reabsorption. Exogenous mineral-corticoid prevents the diuresis, saluresis, and kaluresis. The adequacy of other nonatrial volume control mechanisms in regulating renal salt and water conservation in opposition to the studied atrial-renal (Henry-Gauer) reflex of thoracic vascular distension is confirmed.

Distal renal tubular acidosis in two children with acquired hypothyroidism.

PubMed

Guerra-Hernández, Norma E; Ordaz-López, Karen V; Vargas-Poussou, Rosa; Escobar-Pérez, Laura; García-Nieto, Víctor M

2018-04-28

Two cases of children diagnosed with renal tubular acidosis (RTA) associated with autoimmune hypothyroidism are presented. Case 1 developed an intestinal ileus at the age of five in the context of a respiratory problem. The tests performed confirmed metabolic acidosis, hyperchloraemia, hypokalaemia and nephrocalcinosis. Case 2 was diagnosed with hypothyroidism at the age of 11, and with RTA two years later. In both patients, the diagnosis of RTA was verified when decreased maximum urinary pCO 2 was found. In case 2, a proximal bicarbonate leak (type 3 RTA) was also confirmed. This was the first case to be published on the topic. The causes of RTA in patients with hypothyroidism are reviewed. The deleterious effect on the kidneys may be due to the absence of thyroid hormone and/or autoantibodies in the cases of autoimmune hypothyroidism. Copyright © 2018 Sociedad Española de Nefrología. Published by Elsevier España, S.L.U. All rights reserved.

Modeling oxygen consumption in the proximal tubule: effects of NHE and SGLT2 inhibition

PubMed Central

Vallon, Volker; Edwards, Aurélie

2015-01-01

The objective of this study was to investigate how physiological, pharmacological, and pathological conditions that alter sodium reabsorption (TNa) in the proximal tubule affect oxygen consumption (QO2) and Na+ transport efficiency (TNa/QO2). To do so, we expanded a mathematical model of solute transport in the proximal tubule of the rat kidney. The model represents compliant S1, S2, and S3 segments and accounts for their specific apical and basolateral transporters. Sodium is reabsorbed transcellularly, via apical Na+/H+ exchangers (NHE) and Na+-glucose (SGLT) cotransporters, and paracellularly. Our results suggest that TNa/QO2 is 80% higher in S3 than in S1–S2 segments, due to the greater contribution of the passive paracellular pathway to TNa in the former segment. Inhibition of NHE or Na-K-ATPase reduced TNa and QO2, as well as Na+ transport efficiency. SGLT2 inhibition also reduced proximal tubular TNa but increased QO2; these effects were relatively more pronounced in the S3 vs. the S1–S2 segments. Diabetes increased TNa and QO2 and reduced TNa/QO2, owing mostly to hyperfiltration. Since SGLT2 inhibition lowers diabetic hyperfiltration, the net effect on TNa, QO2, and Na+ transport efficiency in the proximal tubule will largely depend on the individual extent to which glomerular filtration rate is lowered. PMID:25855513

Visualization of Calcium Dynamics in Kidney Proximal Tubules

PubMed Central

Szebényi, Kornélia; Füredi, András; Kolacsek, Orsolya; Csohány, Rózsa; Prókai, Ágnes; Kis-Petik, Katalin; Szabó, Attila; Bősze, Zsuzsanna; Bender, Balázs; Tóvári, József; Enyedi, Ágnes; Orbán, Tamás I.

2015-01-01

Intrarenal changes in cytoplasmic calcium levels have a key role in determining pathologic and pharmacologic responses in major kidney diseases. However, cell-specific delivery of calcium-sensitive probes in vivo remains problematic. We generated a transgenic rat stably expressing the green fluorescent protein-calmodulin–based genetically encoded calcium indicator (GCaMP2) predominantly in the kidney proximal tubules. The transposon-based method used allowed the generation of homozygous transgenic rats containing one copy of the transgene per allele with a defined insertion pattern, without genetic or phenotypic alterations. We applied in vitro confocal and in vivo two-photon microscopy to examine basal calcium levels and ligand- and drug-induced alterations in these levels in proximal tubular epithelial cells. Notably, renal ischemia induced a transient increase in cellular calcium, and reperfusion resulted in a secondary calcium load, which was significantly decreased by systemic administration of specific blockers of the angiotensin receptor and the Na-Ca exchanger. The parallel examination of in vivo cellular calcium dynamics and renal circulation by fluorescent probes opens new possibilities for physiologic and pharmacologic investigations. PMID:25788535

Comparative acute nephrotoxicity of salicylic acid, 2,3-dihydroxybenzoic acid, and 2,5-dihydroxybenzoic acid in young and middle aged Fischer 344 rats.

PubMed

McMahon, T F; Stefanski, S A; Wilson, R E; Blair, P C; Clark, A M; Birnbaum, L S

1991-03-11

Experimental evidence suggests that the oxidative metabolites 2,3- and 2,5-dihydroxybenzoic acid (DIOH) may be responsible for the nephrotoxicity of salicylic acid (SAL). In the present study, enzymuria in conjunction with glucose (GLU) and protein (PRO) excretion were used as endpoints to compare the relative nephrotoxicity of SAL with 2,3- and 2,5-DIOH. In addition, the effect of age on enzymuria and GLU and PRO excretion following treatment with SAL or 2,3- and 2,5-DIOH was investigated because the elderly are at greater risk for SAL-induced nephrotoxicity. Three and 12-month male Fischer 344 rats were administered either no treatment, vehicle, SAL, 2,3-DIOH, or 2,5-DIOH at 500 mg/kg p.o. in 5 ml/kg corn oil/DMSO (5:1). Effects of these treatments on functional integrity of renal tissue was assessed from 0--72 h after dosing by measurement of urinary creatinine, GLU, and PRO, as well as excretion of proximal and distal tubular renal enzymes. Enzymes measured as indicators of proximal tubular damage were N-acetyl-beta-glucosaminidase (NAG), gamma glutamyltransferase (GGT), alanine aminotransferase (ALT), and alkaline phosphatase (AP), while urinary lactate dehydrogenase (LD) and aspartate aminotransferase (AST) were measured as indicators of distal tubular damage. In comparison to 3-month vehicle-treated rats, 2,3- and 2,5-DIOH caused a significant increase between 0-8 h in excretion of urinary GLU and activities of AST, NAG, and LD, with peak effects occurring between 4-8 h. Toxic effects of either metabolite were not evident beyond 24 h, and toxicity of 2,5-DIOH was significantly greater in comparison to 2,3-DIOH. SAL treatment resulted in similar effects on enzymuria as well as GLU and PRO excretion, but peak effects did not occur until 16-24 h, and often persisted until 72 h after dosing. Maximal enzymuria in response to SAL treatment was significantly greater in 12- vs. 3-month rats for AST, NAG, and LD. In response to 2,3-DIOH treatment, the maximal response was significantly greater in 12- vs. 3-month rats for LD and AST, and for NAG in response to 2,5-DIOH treatment. The results of this study suggest that both 2,3- and 2,5-DIOH are nephrotoxic metabolites of SAL, but implicate 2,5-DIOH as the more potent nephrotoxic metabolite. The relative lack of an age effect for 2,3- and 2,5-DIOH vs. SAL supports the hypothesis [2] that age-related differences in biotransformation of SAL, and not increased tissue sensitivity to 2,3- or 2,5-DIOH, contribute to the age-related increase in susceptibility to SAL-induced nephrotoxicity.

SGLT2 inhibition in the diabetic kidney – an update

PubMed Central

Novikov, Aleksandra; Vallon, Volker

2016-01-01

Purpose of review The sodium glucose cotransporter SGLT2 reabsorbs most of the glucose filtered by the kidneys. SGLT2 inhibitors reduce glucose reabsorption thereby lowering blood glucose levels and have been approved as new anti-hyperglycemic drugs. While the therapeutic strategy is very promising, many questions remain. Recent findings Using validated antibodies SGLT2 expression was localized to the brush border of the early proximal tubule in human kidney and was found upregulated in genetic murine models of type 1 and 2 diabetes. SGLT2 may functionally interact with the Na/H exchanger NHE3 in the proximal tubule. SGLT1-mediated reabsorption explains the fractional glucose reabsorption of 40–50% during SGLT2 inhibition. SGLT2 is expressed on pancreatic alpha cells where its inhibition induces glucagon secretion. SGLT2 inhibition lowers GFR in hyperfiltering diabetic patients consistent with the tubular hypothesis of diabetic hyperfiltration. New data indicate a potential of SGLT2 inhibition for renal medullary hypoxia and ketoacidosis, but also for blood glucose effect-dependent and independent nephroprotective actions, renal gluconeogenesis inhibition, reduction in cardiovascular mortality, and cancer therapy. Summary The findings expand and refine our understanding of SGLT2 and its inhibition, have relevance for clinical practice, and will help interpret ongoing clinical trials on the long-term safety and cardiovascular effects of SGLT2 inhibitors. PMID:26575393

EXPERIMENTAL STUDIES IN ACUTE RENAL FAILURE

PubMed Central

Menefee, Max G.; Mueller, C. Barber; Miller, Tracy B.; Myers, Joseph K.; Bell, Allen L.

1964-01-01

When purified human globin is injected intravenously into rats it produces acute renal failure characterized by tubular casts and oliguria. The globin is identifiable within vesicles and channels in the cytoplasm of the proximal tubules, through which it passes from lumen to basal side with no apparent serious effect on the cells. When a very minimal amount of globin is taken up by cells of the distal limb of Henle's loop or distal tubules (lower nephron), a markedly deleterious effect is apparent and the cells die within a short time. The mixture of cell debris and precipitated globin forms plugs within the confines of the basement membranes of the former distal limbs and distal tubules. After a number of lower nephrons are plugged a disruption of proximal tubules is found, which apparently results from the effect of back pressure in the obstructed nephrons. We suggest that any amount in excess of a low threshold of globin, either alone or combined with heme or related material, has a toxic effect on lower nephron cells. Once initiated, the toxic effect is not reversible and the resulting plug of debris and precipitate will occlude the lumen. If a sufficient number of nephrons are made non-functional the animal becomes anuric; otherwise it is oliguric. A high rate of urine flow will protect against the excess absorption of material and thus against acute renal failure. PMID:14238931

Erysipelas in a free-ranging Hawaiian crow (Corvus hawaiiensis)

USGS Publications Warehouse

Work, Thierry M.; Ball, Donna; Wolcott, Mark

1999-01-01

We describe a case of erysipelas in a free-ranging endangered Hawaiian crow. The partially scavenged carcass exhibited gross emaciation and petechial hemorrhages in both lungs. Microscopy revealed multiple necrotic foci associated with gram-positive rods in the liver and adrenal, diffuse acute proximal tubular necrosis of kidney, diffuse necrosis and inflammation of proventricular mucosa associated with gram-positive rods, and multiple intravascular aggregates of gram-positive rods associated with thrombi. Culture of the kidney revealed the bacterium to be Erysipelothrix rhusiopathiae. The implications of this finding to free-ranging crows remain unclear.

The polyuria of paroxysmal atrial tachycardia

NASA Technical Reports Server (NTRS)

Kinney, M. J.; Stein, R. M.; Discala, V. A.

1974-01-01

Two patients with paroxysmal atrial fibrillation and an associated polyuria were studied to delineate the mechanism of the increase in urine flow. A striking saluresis was noted in both patients. The increased sodium excretion was probably due to decreased sodium reabsorption, perhaps at proximal tubular nephron sites. This inhibition of sodium reabsorption could explain both the saluresis and some part or all of the polyuria. Re-evaluation of earlier case reports reveals patterns of concomitant salt and water excretion consistent with this mechanism. The saluresis cannot be explained by the previously favored hypothesis of antidiuretic hormone inhibition.

[Mechanism of renal elimination of 2 elements of group IIIA of the periodic table : aluminum and indium].

PubMed

Galle, P

1981-01-05

Aluminium and indium, two elements of group IIIA of the periodic table, are concentrated by the kidney inside lysosomes of proximal tubule cell. In these lysosomes, aluminium and indium are precipitated as non-soluble phosphate salts and these precipitates are then expelled in the tubular lumen and eliminated with the urinary flow. These data have been visualized by analytical microscopy (ion microscopy and X ray microanalysis). Local acid phosphatases are assumed to permit the concentration of aluminium and indium salts inside the lysosomes.

Hyperglycemia induced damage to mitochondrial respiration in renal mesangial and tubular cells: Implications for diabetic nephropathy.

PubMed

Czajka, Anna; Malik, Afshan N

2016-12-01

Damage to renal tubular and mesangial cells is central to the development of diabetic nephropathy (DN), a complication of diabetes which can lead to renal failure. Mitochondria are the site of cellular respiration and produce energy in the form of ATP via oxidative phosphorylation, and mitochondrial dysfunction has been implicated in DN. Since the kidney is an organ with high bioenergetic needs, we postulated that hyperglycemia causes damage to renal mitochondria resulting in bioenergetic deficit. The bioenergetic profiles and the effect of hyperglycemia on cellular respiration of human primary mesangial (HMCs) and proximal tubular cells (HK-2) were compared in normoglycemic and hyperglycemic conditions using the seahorse bio-analyzer. In normoglycemia, HK-2 had significantly lower basal, ATP-linked and maximal respiration rates, and lower reserve capacity compared to HMCs. Hyperglycemia caused a down-regulation of all respiratory parameters within 4 days in HK-2 but not in HMCs. After 8 days of hyperglycemia, down-regulation of respiratory parameters persisted in tubular cells with compensatory up-regulated glycolysis. HMCs had reduced maximal respiration and reserve capacity at 8 days, and by 12 days had compromised mitochondrial respiration despite which they did not enhance glycolysis. These data suggest that diabetes is likely to lead to a cellular deficit in ATP production in both cell types, although with different sensitivities, and this mechanism could significantly contribute to the cellular damage seen in the diabetic kidney. Prevention of diabetes induced damage to renal mitochondrial respiration may be a novel therapeutic approach for the prevention/treatment of DN. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Beneficial Effects of Myo-Inositol Oxygenase Deficiency in Cisplatin-Induced AKI

PubMed Central

Dutta, Rajesh K.; Kondeti, Vinay K.; Sharma, Isha; Chandel, Navdeep S.; Quaggin, Susan E.

2017-01-01

Overexpression of the proximal tubular enzyme myo-inositol oxygenase (MIOX) induces oxidant stress in vitro. However, the relevance of MIOX to tubular pathobiology remains enigmatic. To investigate the role of MIOX in cisplatin-induced tubular AKI, we generated conditional MIOX-overexpressing transgenic (MIOX-TG) mice and MIOX-knockout (MIOX−/−) mice with tubule-specific MIOX overexpression or knockout, respectively. Compared with cisplatin-treated wild-type (WT) mice, cisplatin-treated MIOX-TG mice had even greater increases in urea, creatinine, and KIM-1 levels and more tubular injury and apoptosis, but these effects were attenuated in cisplatin-treated MIOX−/− mice. Similarly, MIOX-TG mice had the highest and MIOX−/− mice had the lowest renal levels of Bax, cleaved caspase-3, and NADPH oxidase-4 expression and reactive oxygen species (ROS) generation after cisplatin treatment. In vitro, cisplatin dose-dependently increased ROS generation in LLC-PK1 cells. Furthermore, MIOX overexpression in these cells accentuated cisplatin-induced ROS generation and perturbations in the ratio of GSH to oxidized GSH, whereas MIOX-siRNA or N-acetyl cysteine treatment attenuated these effects. Additionally, the cisplatin-induced enhancement of p53 activation, NF-κB binding to DNA, and NF-κB nuclear translocation in WT mice was exacerbated in MIOX-TG mice but absent in MIOX−/− mice. In vitro, MIOX-siRNA or NAC treatment reduced the dose-dependent increase in p53 expression induced by cisplatin. We also observed a remarkable influx of inflammatory cells and upregulation of cytokines in kidneys of cisplatin-treated MIOX-TG mice. Finally, analysis of genomic DNA in WT mice revealed cisplatin-induced hypomethylation of the MIOX promoter. These data suggest that MIOX overexpression exacerbates, whereas MIOX gene disruption protects against, cisplatin-induced AKI. PMID:27895157

Acute and cumulative effects of carboplatin on renal function.

PubMed Central

Sleijfer, D. T.; Smit, E. F.; Meijer, S.; Mulder, N. H.; Postmus, P. E.

1989-01-01

Carboplatin, a cisplatinum analogue, has no reported nephrotoxicity in phase I/II studies, assessed by creatinine clearance. We prospectively determined renal function in 10 untreated lung cancer patients with normal baseline renal function, treated with carboplatin 400 mg m-2 day 1 and vincristine 2 mg day 1 and 8 every 4 weeks (max. five cycles) by means of clearance studies with 125I-sodium thalamate and 131I-hippurate to determine GFR and ERPF respectively. Tubular damage was monitored by excretion of tubular enzymes and relative beta 2-microglobulin clearance. During the first course no changes in renal function were seen. After the second course a significant fall in GFR and ERPF started, ultimately leading to a median decrease in GFR of 19.0% (range 6.8-38.7%) and in ERPF of 14% (range 0-38.9%). No increases in the excretion of tubular enzymes or changes in the relative beta 2-microglobulin clearances were seen. We conclude from our data that carboplatin causes considerable loss of renal function. Monitoring renal function in patients treated with multiple courses of carboplatin is warranted. PMID:2679841

Reduced cholesterol levels in renal membranes of undernourished rats may account for urinary Na⁺ loss.

PubMed

Oliveira, Fabiana S T; Vieira-Filho, Leucio D; Cabral, Edjair V; Sampaio, Luzia S; Silva, Paulo A; Carvalho, Vera C O; Vieyra, Adalberto; Einicker-Lamas, Marcelo; Lima, Vera L M; Paixão, Ana D O

2013-04-01

It has been demonstrated that reabsorption of Na⁺ in the thick ascending limb is reduced and the ability to concentrate urine can be compromised in undernourished individuals. Alterations in phospholipid and cholesterol content in renal membranes, leading to Na⁺ loss and the inability to concentrate urine, were investigated in undernourished rats. Sixty-day-old male Wistar rats were utilized to evaluate (1) phospholipid and cholesterol content in the membrane fraction of whole kidneys, (2) cholesterol content and the levels of active Na⁺ transporters, (Na⁺ + K⁺)ATPase and Na⁺-ATPase, in basolateral membranes of kidney proximal tubules, and (3) functional indicators of medullary urine concentration. Body weight in the undernourished group was 73 % lower than in control. Undernourishment did not affect the levels of cholesterol in serum or in renal homogenates. However, membranes of whole kidneys revealed 56 and 66 % reduction in the levels of total phospholipids and cholesterol, respectively. Furthermore, cholesterol and (Na⁺ + K⁺)ATPase activity in proximal tubule membranes were reduced by 55 and 68 %, respectively. Oxidative stress remained unaltered in the kidneys of undernourished rats. In contrast, Na⁺-ATPase activity, an enzyme with all regulatory components in membrane, was increased in the proximal tubules of undernourished rats. Free water clearance and fractional Na⁺ excretion were increased by 86 and 24 %, respectively, and urinary osmolal concentration was 21 % lower in undernourished rats than controls. Life-long undernutrition reduces the levels of total phospholipids and cholesterol in membranes of renal tubular cells. This alteration in membrane integrity could diminish (Na⁺ + K⁺)ATPase activity resulting in reduced Na⁺ reabsorption and urinary concentrating ability.

Macrophage and epithelial cell H-ferritin expression regulates renal inflammation

PubMed Central

Bolisetty, Subhashini; Zarjou, Abolfazl; Hull, Travis D.; Traylor, Amie; Perianayagam, Anjana; Joseph, Reny; Kamal, Ahmed I; Arosio, Paolo; Soares, Miguel P; Jeney, Viktoria; Balla, Jozsef; George, James F.; Agarwal, Anupam

2015-01-01

Inflammation culminating in fibrosis contributes to progressive kidney disease. Crosstalk between the tubular epithelium and interstitial cells regulates inflammation by a coordinated release of cytokines and chemokines. Here we studied the role of heme oxygenase-1 (HO-1) and the heavy subunit of ferritin (FtH) in macrophage polarization and renal inflammation. Deficiency in HO-1 was associated with increased FtH expression, accumulation of macrophages with a dysregulated polarization profile, and increased fibrosis following unilateral ureteral obstruction in mice; a model of renal inflammation and fibrosis. Macrophage polarization in vitro was predominantly dependent on FtH expression in isolated bone marrow-derived mouse monocytes. Utilizing transgenic mice with conditional deletion of FtH in the proximal tubules (FtHPT−/−) or myeloid cells (FtHLysM−/−), we found that myeloid FtH deficiency did not affect polarization or accumulation of macrophages in the injured kidney compared to wild-type (FtH+/+) controls. However, tubular FtH deletion led to a marked increase in pro-inflammatory macrophages. Furthermore, injured kidneys from FtHPT−/− mice expressed significantly higher levels of inflammatory chemokines and fibrosis compared to kidneys from FtH+/+ and FtHLysM−/− mice. Thus, there are differential effects of FtH in macrophages and epithelial cells, which underscores the critical role of FtH in tubular-macrophage crosstalk during kidney injury. PMID:25874599

The Tuberin/mTOR Pathway Promotes Apoptosis of Tubular Epithelial Cells in Diabetes

PubMed Central

Velagapudi, Chakradhar; Bhandari, Basant S.; Abboud-Werner, Sherry; Simone, Simona; Abboud, Hanna E.

2011-01-01

Apoptosis contributes to the development of diabetic nephropathy, but the mechanism by which high glucose (HG) induces apoptosis is not fully understood. Because the tuberin/mTOR pathway can modulate apoptosis, we studied the role of this pathway in apoptosis in type I diabetes and in cultured proximal tubular epithelial (PTE) cells exposed to HG. Compared with control rats, diabetic rats had more apoptotic cells in the kidney cortex. Induction of diabetes also increased phosphorylation of tuberin in association with mTOR activation (measured by p70S6K phosphorylation), inactivation of Bcl-2, increased cytosolic cytochrome c expression, activation of caspase 3, and cleavage of PARP; insulin treatment prevented these changes. In vitro, exposure of PTE cells to HG increased phosphorylation of tuberin and p70S6K, phosphorylation of Bcl-2, expression of cytosolic cytochrome c, and caspase 3 activity. High glucose induced translocation of the caspase substrate YY1 from the cytoplasm to the nucleus and enhanced cleavage of PARP. Pretreatment the cells with the mTOR inhibitor rapamycin reduced the number of apoptotic cells induced by HG and the downstream effects of mTOR activation noted above. Furthermore, gene silencing of tuberin with siRNA decreased cleavage of PARP. These data show that the tuberin/mTOR pathway promotes apoptosis of tubular epithelial cells in diabetes, mediated in part by cleavage of PARP by YY1. PMID:21289215

The renal response to potassium stress: integrating past with present.

PubMed

Boyd-Shiwarski, Cary R; Subramanya, Arohan R

2017-09-01

The current review combines past findings with recent advances in our understanding of the homeostatic response to potassium imbalance. Following the ingestion of a dietary potassium load, a combination of extrarenal and renal mechanisms act to maintain extracellular K+ within a tight window. Through hormonal regulation and direct K+ sensing, the nephron is ideally suited to respond to wide shifts in external K+ balance. Current evidence indicates that dietary K+ loading triggers a coordinated kaliuretic response that appears to involve voltage-dependent changes in sodium transport across multiple nephron segments, including the proximal tubule, medullary loop of Henle, and distal tubule. Inhibition of sodium transport in these segments would accomplish the final goal of enhancing distal NaCl delivery, luminal flow, and K+ secretion in the aldosterone sensitive distal nephron (ASDN). Ongoing research seeks to define the relationship between potassium and volume homeostasis by elucidating pathways that couple renal K+ sensing and tubular function during the potassium stress response.

Worsening Renal Function in Patients With Acute Heart Failure Undergoing Aggressive Diuresis Is Not Associated With Tubular Injury.

PubMed

Ahmad, Tariq; Jackson, Keyanna; Rao, Veena S; Tang, W H Wilson; Brisco-Bacik, Meredith A; Chen, Horng H; Felker, G Michael; Hernandez, Adrian F; O'Connor, Christopher M; Sabbisetti, Venkata S; Bonventre, Joseph V; Wilson, F Perry; Coca, Steven G; Testani, Jeffrey M

2018-05-08

Worsening renal function (WRF) in the setting of aggressive diuresis for acute heart failure treatment may reflect renal tubular injury or simply indicate a hemodynamic or functional change in glomerular filtration. Well-validated tubular injury biomarkers, N -acetyl-β-d-glucosaminidase, neutrophil gelatinase-associated lipocalin, and kidney injury molecule 1, are now available that can quantify the degree of renal tubular injury. The ROSE-AHF trial (Renal Optimization Strategies Evaluation-Acute Heart Failure) provides an experimental platform for the study of mechanisms of WRF during aggressive diuresis for acute heart failure because the ROSE-AHF protocol dictated high-dose loop diuretic therapy in all patients. We sought to determine whether tubular injury biomarkers are associated with WRF in the setting of aggressive diuresis and its association with prognosis. Patients in the multicenter ROSE-AHF trial with baseline and 72-hour urine tubular injury biomarkers were analyzed (n=283). WRF was defined as a ≥20% decrease in glomerular filtration rate estimated with cystatin C. Consistent with protocol-driven aggressive dosing of loop diuretics, participants received a median 560 mg IV furosemide equivalents (interquartile range, 300-815 mg), which induced a urine output of 8425 mL (interquartile range, 6341-10 528 mL) over the 72-hour intervention period. Levels of N -acetyl-β-d-glucosaminidase and kidney injury molecule 1 did not change with aggressive diuresis (both P >0.59), whereas levels of neutrophil gelatinase-associated lipocalin decreased slightly (-8.7 ng/mg; interquartile range, -169 to 35 ng/mg; P <0.001). WRF occurred in 21.2% of the population and was not associated with an increase in any marker of renal tubular injury: neutrophil gelatinase-associated lipocalin ( P =0.21), N -acetyl-β-d-glucosaminidase ( P =0.46), or kidney injury molecule 1 ( P =0.22). Increases in neutrophil gelatinase-associated lipocalin, N -acetyl-β-d-glucosaminidase, and kidney injury molecule 1 were paradoxically associated with improved survival (adjusted hazard ratio, 0.80 per 10 percentile increase; 95% confidence interval, 0.69-0.91; P =0.001). Kidney tubular injury does not appear to have an association with WRF in the context of aggressive diuresis of patients with acute heart failure. These findings reinforce the notion that the small to moderate deteriorations in renal function commonly encountered with aggressive diuresis are dissimilar from traditional causes of acute kidney injury. © 2018 American Heart Association, Inc.

Bubble-Free Propulsion of Ultrasmall Tubular Nanojets Powered by Biocatalytic Reactions.

PubMed

Ma, Xing; Hortelao, Ana C; Miguel-López, Albert; Sánchez, Samuel

2016-10-26

The motion of self-propelled tubular micro- and nanojets has so far been achieved by bubble propulsion, e.g., O 2 bubbles formed by catalytic decomposition of H 2 O 2 , which renders future biomedical applications inviable. An alternative self-propulsion mechanism for tubular engines on the nanometer scale is still missing. Here, we report the fabrication and characterization of bubble-free propelled tubular nanojets (as small as 220 nm diameter), powered by an enzyme-triggered biocatalytic reaction using urea as fuel. We studied the translational and rotational dynamics of the nanojets as functions of the length and location of the enzymes. Introducing tracer nanoparticles into the system, we demonstrated the presence of an internal flow that extends into the external fluid via the cavity opening, leading to the self-propulsion. One-dimensional nanosize, longitudinal self-propulsion, and biocompatibility make the tubular nanojets promising for future biomedical applications.

Use of urinary γ-glutamyl transferase (GGT) to monitor the pattern of proteinuria in dogs with leishmaniasis treated with N-methylglucamine antimoniate.

PubMed

Paltrinieri, Saverio; Mangiagalli, Giulia; Ibba, Fabrizio

2018-05-25

The aim of this study was to assess if the coupled analysis of the urinary protein to creatinine (UPC) ratio and of the GGT/UC ratio (the ratio between urinary γ-glutamyl transferase activity and urinary creatinine) may be used in treated leishmaniotic dogs to differentiate dogs with transient impairment of tubular function from dogs with persistent tubular damage. To this aim, 40 urine from 10 proteinuric and leishmaniotic dogs that at the first visit had high GGT/UC ratio, consistent with tubular damage, were collected and analyzed before treatments and 2, 4 and 6 weeks after treatment with N-methylglucamine antimoniate and allopurinol. Compared with pre-treatment values, at the end of the study period the UPC ratio decreased only in 5/10 dogs, which, however, were still proteinuric or borderline proteinuric. Conversely, the GGT/CU ratio decreased in 8/10 dogs and in 3 of them the values at the end of the study period were below the threshold consistent with tubular proteinuria. The GGT/UC values at 6 weeks was significantly lower than before treatment. However, transient increases were frequent for both the analytes. These results indicate that in most of the dogs that remain proteinuric after treatment, likely due to the persistent glomerular damage, the GGT/UC ratio tends to normalize. This suggests that in these dogs tubular proteinuria at admission depends on functional impairment of tubular cells likely due to the overflow of proteins from damaged glomeruli. However, tubular proteinuria occasionally persists, suggesting that tubulointerstitial damages persist even in dogs responsive to treatments. Copyright © 2018 Elsevier Ltd. All rights reserved.

Inversin relays Frizzled-8 signals to promote proximal pronephros development

PubMed Central

Lienkamp, Soeren; Ganner, Athina; Boehlke, Christopher; Schmidt, Thorsten; Arnold, Sebastian J.; Schäfer, Tobias; Romaker, Daniel; Schuler, Julia; Hoff, Sylvia; Powelske, Christian; Eifler, Annekathrin; Krönig, Corinna; Bullerkotte, Axel; Nitschke, Roland; Kuehn, E. Wolfgang; Kim, Emily; Burkhardt, Hans; Brox, Thomas; Ronneberger, Olaf; Gloy, Joachim; Walz, Gerd

2010-01-01

Mutations of inversin cause type II nephronophthisis, an infantile autosomal recessive disease characterized by cystic kidney disease and developmental defects. Inversin regulates Wnt signaling and is required for convergent extension movements during early embryogenesis. We now show that Inversin is essential for Xenopus pronephros formation, involving two distinct and opposing forms of cell movements. Knockdown of Inversin abrogated both proximal pronephros extension and distal tubule differentiation, phenotypes similar to that of Xenopus deficient in Frizzled-8. Exogenous Inversin rescued the pronephric defects caused by lack of Frizzled-8, indicating that Inversin acts downstream of Frizzled-8 in pronephros morphogenesis. Depletion of Inversin prevents the recruitment of Dishevelled in response to Frizzled-8 and impeded the accumulation of Dishevelled at the apical membrane of tubular epithelial cells in vivo. Thus, defective tubule morphogenesis seems to contribute to the renal pathology observed in patients with nephronophthisis type II. PMID:21059920

Bcl-2 protects tubular epithelial cells from ischemia/reperfusion injury by dual mechanisms.

PubMed

Isaka, Y; Suzuki, C; Abe, T; Okumi, M; Ichimaru, N; Imamura, R; Kakuta, Y; Matsui, I; Takabatake, Y; Rakugi, H; Shimizu, S; Takahara, S

2009-01-01

Ischemia/reperfusion (I/R) injury, which induces extensive loss of tubular epithelial cells, is associated with delayed graft function following kidney transplantation. Recent reports have suggested that cell death by I/R injury occurs by autophagy, a cellular degradation process responsible for the turnover of unnecessary or dysfunctional organelles and cytoplasmic proteins, as well as by apoptosis. Recently, we demonstrated that overexpression of the anti-apoptotic factor, Bcl-2, inhibited tubular apoptosis and subsequent tubulointerstitial damage after I/R injury. Autophagy is also observed in cells undergoing cell death in several diseases. Therefore, we hypothesized that increased Bcl-2 protein may protect tubular epithelial cells by suppressing autophagy and inhibiting apoptosis. In the present study, a transgenic mouse model (LC3-GFP TG) in which autophagosomes are labeled with LC3-GFP and Bcl-2/LC3-GFP double transgenic mice (Bcl-2/LC3-GFP TG) were used to examine the effect of Bcl-2 on I/R-induced autophagy. I/R injury, which is associated with marked disruption of normal tubular morphology, promoted the formation of LC3-GFP dots, representing extensively induced autophagosomes. On electron microscopy, the autophagosomes contained mitochondria in I/R-injured tubular epithelial cells. In contrast, Bcl-2 augmentation suppressed the formation of autophagosomes and there was less tubular damage. In conclusion, Bcl-2 augmentation protected renal tubular epithelial cells from I/R injury by suppressing autophagosomal degradation and inhibiting tubular apoptosis.

Proximal tubulopathies associated with monoclonal light chains: the spectrum of clinicopathologic manifestations and molecular pathogenesis.

PubMed

Herrera, Guillermo A

2014-10-01

Lesions associated with monoclonal light and heavy chains display a variety of glomerular, tubular interstitial, and vascular manifestations. While some of the entities are well recognized, including light and heavy chain deposition diseases, AL (light chain) and AH (heavy chain) amyloidosis, and light chain ("myeloma") cast nephropathy, other lesions centered on proximal tubules are much less accurately identified, properly diagnosed, and adequately understood in terms of pathogenesis and molecular mechanisms involved. These proximal tubule-centered lesions are typically associated with monoclonal light chains and have not been reported in patients with circulating monoclonal heavy chains. To determine the incidence of proximal tubulopathies in a series of patients with monoclonal light chain-related renal lesions and characterize them with an emphasis on clinical correlations and elucidation of molecular mechanisms involved in their pathogenesis. A study of 5410 renal biopsies with careful evaluation of light microscopic, immunofluorescence, and electron microscopic findings was conducted to identify these monoclonal light/heavy chain-related lesions. In selected cases, ultrastructural immunolabeling was performed to better illustrate and understand molecular mechanisms involved or to resolve specific diagnostic difficulties. In all, 2.5% of the biopsies were diagnosed as demonstrating renal pathology associated with monoclonal light or heavy chains. Of these, approximately 46% were classified as proximal tubule-centered lesions, also referred to as monoclonal light chain-associated proximal tubulopathies. These proximal tubulopathies were divided into 4 groups defined by characteristic immunomorphologic manifestations associated with specific clinical settings. These are important lesions whose recognition in the different clinical settings is extremely important for patients' clinical management, therapeutic purposes, and prognosis. These entities have been segregated into 4 distinct variants, conceptualized morphologically and clinically. Specific mechanisms involved in their pathogenesis are proposed.

Cooperation of Antiporter LAT2/CD98hc with Uniporter TAT1 for Renal Reabsorption of Neutral Amino Acids.

PubMed

Vilches, Clara; Boiadjieva-Knöpfel, Emilia; Bodoy, Susanna; Camargo, Simone; López de Heredia, Miguel; Prat, Esther; Ormazabal, Aida; Artuch, Rafael; Zorzano, Antonio; Verrey, François; Nunes, Virginia; Palacín, Manuel

2018-04-02

Background Reabsorption of amino acids (AAs) across the renal proximal tubule is crucial for intracellular and whole organism AA homeostasis. Although the luminal transport step is well understood, with several diseases caused by dysregulation of this process, the basolateral transport step is not understood. In humans, only cationic aminoaciduria due to malfunction of the basolateral transporter y + LAT1/CD98hc (SLC7A7/SLC3A2), which mediates the export of cationic AAs, has been described. Thus, the physiologic roles of basolateral transporters of neutral AAs, such as the antiporter LAT2/CD98hc (SLC7A8/SLC3A2), a heterodimer that exports most neutral AAs, and the uniporter TAT1 (SLC16A10), which exports only aromatic AAs, remain unclear. Functional cooperation between TAT1 and LAT2/CD98hc has been suggested by in vitro studies but has not been evaluated in vivo Methods To study the functional relationship of TAT1 and LAT2/CD98hc in vivo , we generated a double-knockout mouse model lacking TAT1 and LAT2, the catalytic subunit of LAT2/CD98hc (dKO LAT2-TAT1 mice). Results Compared with mice lacking only TAT1 or LAT2, dKO LAT2-TAT1 mice lost larger amounts of aromatic and other neutral AAs in their urine due to a tubular reabsorption defect. Notably, dKO mice also displayed decreased tubular reabsorption of cationic AAs and increased expression of y + LAT1/CD98hc. Conclusions The LAT2/CD98hc and TAT1 transporters functionally cooperate in vivo , and y + LAT1/CD98hc may compensate for the loss of LAT2/CD98hc and TAT1, functioning as a neutral AA exporter at the expense of some urinary loss of cationic AAs. Cooperative and compensatory mechanisms of AA transporters may explain the lack of basolateral neutral aminoacidurias in humans. Copyright © 2018 by the American Society of Nephrology.

Post-hypoxic cellular disintegration in glycine-preserved renal tubules is attenuated by hydroxyl radical scavengers and iron chelators.

PubMed

Moussavian, Mohammed R; Slotta, Jan E; Kollmar, Otto; Menger, Michael D; Gronow, Gernot; Schilling, Martin K

2008-05-01

Cellular stress during reoxygenation is a common phenomenon in solid organ transplantation and is characterized by production of reactive oxygen species. Herein, we studied in isolated tubular segments of rat kidney cortex the impact of oxygen radical scavengers and an iron chelator on post-hypoxic recovery. Tubules, suspended in Ringer's solution containing 5 mM glycine, underwent 30 min hypoxia and 60 min reoxygenation. Untreated tubules served as controls. Hypoxia-reoxygenation injury was measured by membrane leakage, lipid peroxidation and cellular functions. In hypoxia-reoxygenated-isolated tubular segments, protective effects of different scavengers and of the iron chelator deferoxamine on hypoxia-reoxygenation injury were analyzed. Scavengers protected isolated tubular segments from hypoxia-reoxygenation-induced cellular disintegration and dysfunction. Deferoxamine was found to exert the most distinct protection. It was further found to exert a dose-dependent protection on hypoxia-reoxygenation damage in isolated tubular segments, which was critically mediated by chelating tissue and bond iron. Our data demonstrate that radical scavengers effectively protect from hypoxia-reoxygenation injury in isolated tubular segments and that the iron chelator deferoxamine is especially a potent inhibitor of iron ion-mediated hypoxia-reoxygenation damage. Thus, inclusion of this iron chelator in organ storage solutions might improve post-transplant organ function and protect from reperfusion injury.

Hemodynamic and tubular changes induced by contrast media.

PubMed

Caiazza, Antonella; Russo, Luigi; Sabbatini, Massimo; Russo, Domenico

2014-01-01

The incidence of acute kidney injury induced by contrast media (CI-AKI) is the third cause of AKI in hospitalized patients. Contrast media cause relevant alterations both in renal hemodynamics and in renal tubular cell function that lead to CI-AKI. The vasoconstriction of intrarenal vasculature is the main hemodynamic change induced by contrast media; the vasoconstriction is accompanied by a cascade of events leading to ischemia and reduction of glomerular filtration rate. Cytotoxicity of contrast media causes apoptosis of tubular cells with consequent formation of casts and worsening of ischemia. There is an interplay between the negative effects of contrast media on renal hemodynamics and on tubular cell function that leads to activation of renin-angiotensin system and increased production of reactive oxygen species (ROS) within the kidney. Production of ROS intensifies cellular hypoxia through endothelial dysfunction and alteration of mechanisms regulating tubular cells transport. The physiochemical characteristics of contrast media play a critical role in the incidence of CI-AKI. Guidelines suggest the use of either isoosmolar or low-osmolar contrast media rather than high-osmolar contrast media particularly in patients at increased risk of CI-AKI. Older age, presence of atherosclerosis, congestive heart failure, chronic renal disease, nephrotoxic drugs, and diuretics may multiply the risk of CI-AKI.

Neural control of renal function: role of renal alpha adrenoceptors.

PubMed

DiBona, G F

1985-01-01

Adrenoceptors of various subtypes mediate the renal functional responses to alterations in efferent renal sympathetic nerve activity, the neural component, and renal arterial plasma catecholamine concentrations, the humoral component, of the sympathoadrenergic nervous system. Under normal physiologic as well as hypertensive conditions, the influence of the renal sympathetic nerves predominates over that of circulating plasma catecholamines. In most mammalian species, increases in efferent renal sympathetic nerve activity elicit renal vasoconstrictor responses mediated predominantly by renal vascular alpha-1 adrenoceptors, increases in renin release mediated largely by renal juxtaglomerular granular cell beta-1 adrenoceptors with involvement of renal vascular alpha-1 adrenoceptors only when renal vasoconstriction occurs, and direct increases in renal tubular sodium and water reabsorption mediated predominantly by renal tubular alpha-1 adrenoceptors. In most mammalian species, alpha-2 adrenoceptors do not play a significant role in the renal vascular or renin release responses to renal sympathoadrenergic stimulation. Although renal tubular alpha-2 adrenoceptors do not mediate the increases in renal tubular sodium and water reabsorption produced by increases in efferent renal sympathetic nerve activity, they may be involved through their inhibitory effect on adenylate cyclase in modulating the response to other hormonal agents that influence renal tubular sodium and water reabsorption via stimulation of adenylate cyclase.

Hemodynamic and Tubular Changes Induced by Contrast Media

PubMed Central

Caiazza, Antonella; Russo, Luigi; Russo, Domenico

2014-01-01

The incidence of acute kidney injury induced by contrast media (CI-AKI) is the third cause of AKI in hospitalized patients. Contrast media cause relevant alterations both in renal hemodynamics and in renal tubular cell function that lead to CI-AKI. The vasoconstriction of intrarenal vasculature is the main hemodynamic change induced by contrast media; the vasoconstriction is accompanied by a cascade of events leading to ischemia and reduction of glomerular filtration rate. Cytotoxicity of contrast media causes apoptosis of tubular cells with consequent formation of casts and worsening of ischemia. There is an interplay between the negative effects of contrast media on renal hemodynamics and on tubular cell function that leads to activation of renin-angiotensin system and increased production of reactive oxygen species (ROS) within the kidney. Production of ROS intensifies cellular hypoxia through endothelial dysfunction and alteration of mechanisms regulating tubular cells transport. The physiochemical characteristics of contrast media play a critical role in the incidence of CI-AKI. Guidelines suggest the use of either isoosmolar or low-osmolar contrast media rather than high-osmolar contrast media particularly in patients at increased risk of CI-AKI. Older age, presence of atherosclerosis, congestive heart failure, chronic renal disease, nephrotoxic drugs, and diuretics may multiply the risk of CI-AKI. PMID:24678510

Time Course of Pathogenic and Adaptation Mechanisms in Cystinotic Mouse Kidneys

PubMed Central

Gaide Chevronnay, Héloïse P.; Janssens, Virginie; Van Der Smissen, Patrick; N’Kuli, Francisca; Nevo, Nathalie; Guiot, Yves; Levtchenko, Elena; Marbaix, Etienne; Pierreux, Christophe E.; Cherqui, Stéphanie; Antignac, Corinne; Courtoy, Pierre J.

2014-01-01

Cystinosis, a main cause of Fanconi syndrome, is reproduced in congenic C57BL/6 cystinosin knockout (KO) mice. To identify the sequence of pathogenic and adaptation mechanisms of nephropathic cystinosis, we defined the onset of Fanconi syndrome in KO mice between 3 and 6 months of age and analyzed the correlation with structural and functional changes in proximal tubular cells (PTCs), with focus on endocytosis of ultrafiltrated disulfide-rich proteins as a key source of cystine. Despite considerable variation between mice at the same age, typical event sequences were delineated. At the cellular level, amorphous lysosomal inclusions preceded cystine crystals and eventual atrophy without crystals. At the nephron level, lesions started at the glomerulotubular junction and then extended distally. In situ hybridization and immunofluorescence revealed progressive loss of expression of megalin, cubilin, sodium-glucose cotransporter 2, and type IIa sodium-dependent phosphate cotransporter, suggesting apical dedifferentiation accounting for Fanconi syndrome before atrophy. Injection of labeled proteins revealed that defective endocytosis in S1 PTCs led to partial compensatory uptake by S3 PTCs, suggesting displacement of endocytic load and injury by disulfide-rich cargo. Increased PTC apoptosis allowed luminal shedding of cystine crystals and was partially compensated for by tubular proliferation. We conclude that lysosomal storage triggered by soluble cystine accumulation induces apical PTC dedifferentiation, which causes transfer of the harmful load of disulfide-rich proteins to more distal cells, possibly explaining longitudinal progression of swan-neck lesions. Furthermore, our results suggest that subsequent adaptation mechanisms include lysosomal clearance of free and crystalline cystine into urine and ongoing tissue repair. PMID:24525030

Estrogen-related receptor α is essential for maintaining mitochondrial integrity in cisplatin-induced acute kidney injury.

PubMed

Tsushida, Keigo; Tanabe, Katsuyuki; Masuda, Kana; Tanimura, Satoshi; Miyake, Hiromasa; Arata, Yuka; Sugiyama, Hitoshi; Wada, Jun

2018-04-15

Acute kidney injury (AKI) has been associated with not only higher in-hospital mortality but also the subsequent development of chronic kidney disease (CKD). Recent evidence has suggested the involvement of mitochondrial dysfunction and impaired dynamics in the pathogenesis of AKI. Estrogen-related receptor α (ERRα) is an orphan nuclear receptor that acts as a transcription factor to regulate the transcription of genes required for mitochondrial biogenesis and oxidative phosphorylation. In the present study, we examined the effects of ERRα deficiency on the progression of AKI induced by cisplatin. Male C57BL/6 J wild-type and ERRα -/- mice received a single intraperitoneal injection of 20 mg/kg cisplatin. Seventy-two hours after the injection, kidney function and morphology were evaluated. ERRα expression was observed in renal tubules, and cisplatin inhibited its translocation into nuclei. ERRα deficiency exacerbated cisplatin-induced renal dysfunction and tubular injury, as well as oxidative stress and apoptosis. ERRα -/- mice kidneys revealed lower mitochondrial DNA content and swollen mitochondria with reduced cristae. In addition, these mice had lower expression of the mitochondrial fusion protein mitofusin-2. The cisplatin-induced decrease in mitochondrial DNA and altered mitochondrial structure were more severe in ERRα -/- mice. In cultured mouse proximal tubular epithelial cells, the ERRα inverse agonist XCT-790 significantly inhibited mitofusin-2 expression and induced mitochondrial fragmentation. Taken together, our findings suggest the involvement of ERRα in the progression of cisplatin-induced AKI probably through impaired mitochondrial dynamics. Copyright © 2018 Elsevier Inc. All rights reserved.

Acute toxicity induced by 2-aryl-N-methylsuccinimides.

PubMed

Rankin, G O; Shih, H C; Teets, V J; Nicoll, D W; Brown, P I

1990-04-01

Phensuximide (PSX) is a 2-arylsuccinimide useful in the treatment of absence seizures. PSX is a mild urotoxicant and is structurally related to N-phenylsuccinimide (NPS) and its antifungal derivatives. Since substitution of the phenyl ring of NPS with chloro or tert-butyl groups can produce compounds with enhanced nephrotoxic potential, it was felt that similar substitutions on the phenyl ring of PSX also might produce derivatives with enhanced nephrotoxic potential. Three derivatives of PSX were prepared and tested: 2-(3-chlorophenyl)-N-methylsuccinimide (CPMS); 2-(4-tert-butylphenyl)-N-methylsuccinimide (BPMS) and 2-(3,5-dichlorophenyl)-N-methylsuccinimide (DPMS). In one set of experiments, male Fischer 344 rats were administered a single intraperitoneal (i.p.) injection of a succinimide (0.4 or 1.0 mmol kg-1) or vehicle (sesame oil, 2.5 ml kg-1) and renal function monitored at 24 and 48 h. Only minor changes in renal function were noted with the PSX derivatives. BPMS and DPMS (1.0 mmol kg-1) treatment induced mild renal tubular necrosis and thickening of the glomerular membranes. However, no significant morphological changes were noted in ureters, bladder or liver in any treatment group. In a second set of experiments, rats were pretreated with phenobarbital (75 mg kg-1 day-1, i.p., 3 days) followed by a single i.p. injection of DPMS (0.4 or 1.0 mmol kg-1) or DPMS vehicle. Renal function was monitored as before. Phenobarbital pretreatment did not markedly enhance the functional nephrotoxicity induced by DPMS (0.4 mmol), but tubular necrosis was greater than observed in non-phenobarbital-pretreated rats receiving DPMS (1.0 mmol kg-1). In addition, hepatotoxicity was observed as the appearance of numerous non-staining vacuoles in hypertrophied hepatocytes. In the phenobarbital plus DPMS (1.0 mmol kg-1) treatment group, all rats died by 48 h. Prior to death, rats exhibited increased proteinuria (+3), hematuria (+3) and blood urea nitrogen concentration. At 24 h, kidneys from rats treated with phenobarbital plus DPMS (1.0 mmol kg-1) exhibited extensive proximal tubular necrosis and numerous glomeruli with thickened membranes. Hepatotoxicity was more pronounced than with phenobarbital plus DPMS (0.4 mmol kg-1) at 48 h and urinary bladders had focal areas of erythrocytes pooling below the epithelial lining. These results demonstrate that although NPS and PSX are structural analogs, chemical substitutions that enhance the nephrotoxic potential of NPS do not have a similar effect on PSX. In addition, DPMS can induce urotoxicity in a manner similar to that observed for PSX and probably induces toxicity via one or more metabolites.

Inhibition effect of small interfering RNA of connective tissue growth factor on the expression of extracellular matrix molecules in cultured human renal proximal tubular cells.

PubMed

Liu, Yuyuan; Li, Weiwei; Liu, Hong; Peng, Youming; Yang, Qiu; Xiao, Li; Liu, Yinghong; Liu, Fuyou

2014-03-01

In this study, we investigated the effect of small interfering RNA (siRNA) of connective tissue growth factor (CTGF) by pRetro-Super (PRS) retrovirus vector on the expression of CTGF and related extracellular matrix molecules in human renal proximal tubular cells (HKCs) induced by high glucose, to provide help for renal tubulointerstitial fibrosis therapy. HKCs were exposed to d-glucose to observe their dose and time effect, while the mannitol as osmotic control. Retrovirus producing CTGF siRNA were constructed from the inverted oligonucleotides and transferred into packaging cell line PT67 with lipofectamine, and the virus supernatant was used to infect HKC. The expression of CTGF, fibronectin (FN) and collagen-type I (col1) were measured by semi-quantitative RT-PCR and Western blot. In response to high glucose, CTGF expression in HKCs was increased in a dose- and time-dependent manner, whereas the increase did not occur in the osmotic control. Introduction of PRS-CTGF-siRNA resulted in the significant reduction of CTGF, FN, col1 mRNA (p < 0.01, respectively) and CTGF, col1 protein (p < 0.05, respectively) expression, while PRS void vector group did not have these effects (p > 0.05). CTGF siRNA therapy can effectively reduce the levels of CTGF, FN and col1 induced by high glucose in cultured HKCs, which suggested that it may be a potential therapeutic strategy to prevent the renal interstitial fibrosis in the future.

Na+-independent D-glucose transport in rabbit renal basolateral membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheung, P.T.; Hammerman, M.R.

1988-05-01

To define the mechanism by which glucose is transported across the basolateral membrane of the renal proximal tubular cell, we measured D-(14C)glucose uptake in basolateral membrane vesicles from rabbit kidney. Na+-dependent D-glucose transport, demonstrable in brush-border vesicles, could not be demonstrated in basolateral membrane vesicles. In the absence of Na+, the uptake of D-(14C)glucose in basolateral vesicles was more rapid than that of L-(3H)glucose over a concentration range of 1-50 mM. Subtraction of the latter from the former uptakes revealed a saturable process with apparent Km of 9.9 mM and Vmax of 0.80 nmol.mg protein-1.s-1. To characterize the transport componentmore » of D-glucose uptake in basolateral vesicles, we measured trans stimulation of 2 mM D-(14C)glucose entry in the absence of Na+. Trans stimulation could be effected by preloading basolateral vesicles with D-glucose, 2-deoxy-D-glucose, or 3-O-methyl-D-glucose, but not with L-glucose or alpha-methyl-D-glucoside. Trans-stimulated D-(14C)glucose uptake was inhibited by 0.1 mM phloretin or cytochalasin B but not phlorizin. In contrast, Na+-dependent D-(14C)glucose transport in brush-border vesicles was inhibited by phlorizin but not phloretin or cytochalasin B. Our findings are consistent with the presence of a Na+-independent D-glucose transporter in the proximal tubular basolateral membrane with characteristics similar to those of transporters present in nonepithelial cells.« less

Spleen tyrosine kinase mediates high glucose-induced transforming growth factor-{beta}1 up-regulation in proximal tubular epithelial cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Won Seok; Chang, Jai Won; Han, Nam Jeong

The role of spleen tyrosine kinase (Syk) in high glucose-induced intracellular signal transduction has yet to be elucidated. We investigated whether Syk is implicated in high glucose-induced transforming growth factor-{beta}1 (TGF-{beta}1) up-regulation in cultured human proximal tubular epithelial cells (HK-2 cell). High glucose increased TGF-{beta}1 gene expression through Syk, extracellular signal-regulated kinase (ERK), AP-1 and NF-{kappa}B. High glucose-induced AP-1 DNA binding activity was decreased by Syk inhibitors and U0126 (an ERK inhibitor). Syk inhibitors suppressed high glucose-induced ERK activation, whereas U0126 had no effect on Syk activation. High glucose-induced NF-{kappa}B DNA binding activity was also decreased by Syk inhibitors. Highmore » glucose increased nuclear translocation of p65 without serine phosphorylation of I{kappa}B{alpha} and without degradation of I{kappa}B{alpha}, but with an increase in tyrosine phosphorylation of I{kappa}B{alpha} that may account for the activation of NF-{kappa}B. Both Syk inhibitors and Syk-siRNA attenuated high glucose-induced I{kappa}B{alpha} tyrosine phosphorylation and p65 nuclear translocation. Depletion of p21-activated kinase 2 (Pak2) by transfection of Pak2-siRNA abolished high glucose-induced Syk activation. In summary, high glucose-induced TGF-{beta}1 gene transcription occurred through Pak2, Syk and subsequent ERK/AP-1 and NF-{kappa}B pathways. This suggests that Syk might be implicated in the diabetic kidney disease.« less

Optimal startup control of a jacketed tubular reactor.

NASA Technical Reports Server (NTRS)

Hahn, D. R.; Fan, L. T.; Hwang, C. L.

1971-01-01

The optimal startup policy of a jacketed tubular reactor, in which a first-order, reversible, exothermic reaction takes place, is presented. A distributed maximum principle is presented for determining weak necessary conditions for optimality of a diffusional distributed parameter system. A numerical technique is developed for practical implementation of the distributed maximum principle. This involves the sequential solution of the state and adjoint equations, in conjunction with a functional gradient technique for iteratively improving the control function.

A high throughput respirometric assay for mitochondrial biogenesis and toxicity

PubMed Central

Beeson, Craig C.; Beeson, Gyda C.; Schnellmann, Rick G.

2010-01-01

Mitochondria are a common target of toxicity for drugs and other chemicals, and results in decreased aerobic metabolism and cell death. In contrast, mitochondrial biogenesis restores cell vitality and there is a need for new agents to induce biogenesis. Current cell-based models of mitochondrial biogenesis or toxicity are inadequate because cultured cell lines are highly glycolytic with minimal aerobic metabolism and altered mitochondrial physiology. In addition, there are no high-throughput, real-time assays that assess mitochondrial function. We adapted primary cultures of renal proximal tubular cells (RPTC) that exhibit in vivo levels of aerobic metabolism, are not glycolytic, and retain higher levels of differentiated functions and used the Seahorse Biosciences analyzer to measure mitochondrial function in real time in multi-well plates. Using uncoupled respiration as a marker of electron transport chain (ETC) integrity, the nephrotoxicants cisplatin, HgCl2 and gentamicin exhibited mitochondrial toxicity prior to decreases in basal respiration and cell death. Conversely, using FCCP-uncoupled respiration as a marker of maximal ETC activity, 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), SRT1720, resveratrol, daidzein, and metformin produced mitochondrial biogenesis in RPTC. The merger of the RPTC model and multi-well respirometry results in a single high throughput assay to measure mitochondrial biogenesis and toxicity, and nephrotoxic potential. PMID:20465991

Hyperammonemia associated with distal renal tubular acidosis or urinary tract infection: a systematic review.

PubMed

Clericetti, Caterina M; Milani, Gregorio P; Lava, Sebastiano A G; Bianchetti, Mario G; Simonetti, Giacomo D; Giannini, Olivier

2018-03-01

Hyperammonemia usually results from an inborn error of metabolism or from an advanced liver disease. Individual case reports suggest that both distal renal tubular acidosis and urinary tract infection may also result in hyperammonemia. A systematic review of the literature on hyperammonemia secondary to distal renal tubular acidosis and urinary tract infection was conducted. We identified 39 reports on distal renal tubular acidosis or urinary tract infections in association with hyperammonemia published between 1980 and 2017. Hyperammonemia was detected in 13 children with distal renal tubular acidosis and in one adult patient with distal renal tubular acidosis secondary to primary hyperparathyroidism. In these patients a negative relationship was observed between circulating ammonia and bicarbonate levels (P < 0.05). In 31 patients (19 children, 12 adults), an acute urinary tract infection was complicated by acute hyperammonemia and symptoms and signs of acute neuronal dysfunction, such as an altered level of consciousness, convulsions and asterixis, often associated with signs of brain edema, such as anorexia and vomiting. Urea-splitting bacteria were isolated in 28 of the 31 cases. The urinary tract was anatomically or functionally abnormal in 30 of these patients. This study reveals that both altered distal renal tubular acidification and urinary tract infection may be associated with relevant hyperammonemia in both children and adults.

Developmental changes in renal tubular transport - An overview

PubMed Central

Gattineni, Jyothsna; Baum, Michel

2013-01-01

The adult kidney maintains a constant volume and composition of extracellular fluid despite changes in water and salt intake. The neonate is born with a kidney that has a small fraction of the glomerular filtration rate of the adult and immature tubules that function at a lower capacity than that of the mature animal. None the less, the neonate is also able to maintain a constant extracellular fluid volume and composition. Postnatal renal tubular development was once thought to be due to an increase in the transporter abundance to meet the developmental increase in glomerular filtration rate. However, postnatal renal development of each nephron segment is quite complex. There are isoform changes of several transporters as well as developmental changes in signal transduction that affect the capacity of renal tubules to reabsorb solutes and water. This review will discuss neonatal tubular function with an emphasis on the differences that have been found between the neonate and adult. We will also discuss some of the factors that are responsible for the maturational changes in tubular transport that occur during postnatal renal development. PMID:24253590

Developmental changes in renal tubular transport-an overview.

PubMed

Gattineni, Jyothsna; Baum, Michel

2015-12-01

The adult kidney maintains a constant volume and composition of extracellular fluid despite changes in water and salt intake. The neonate is born with a kidney that has a small fraction of the glomerular filtration rate of the adult and immature tubules that function at a lower capacity than that of the mature animal. Nonetheless, the neonate is also able to maintain a constant extracellular fluid volume and composition. Postnatal renal tubular development was once thought to be due to an increase in the transporter abundance to meet the developmental increase in glomerular filtration rate. However, postnatal renal development of each nephron segment is quite complex. There are isoform changes of several transporters as well as developmental changes in signal transduction that affect the capacity of renal tubules to reabsorb solutes and water. This review will discuss neonatal tubular function with an emphasis on the differences that have been found between the neonate and adult. We will also discuss some of the factors that are responsible for the maturational changes in tubular transport that occur during postnatal renal development.

Drosophila as a model for epithelial tube formation.

PubMed

Maruyama, Rika; Andrew, Deborah J

2012-01-01

Epithelial tubular organs are essential for life in higher organisms and include the pancreas and other secretory organs that function as biological factories for the synthesis and delivery of secreted enzymes, hormones, and nutrients essential for tissue homeostasis and viability. The lungs, which are necessary for gas exchange, vocalization, and maintaining blood pH, are organized as highly branched tubular epithelia. Tubular organs include arteries, veins, and lymphatics, high-speed passageways for delivery and uptake of nutrients, liquids, gases, and immune cells. The kidneys and components of the reproductive system are also epithelial tubes. Both the heart and central nervous system of many vertebrates begin as epithelial tubes. Thus, it is not surprising that defects in tube formation and maintenance underlie many human diseases. Accordingly, a thorough understanding how tubes form and are maintained is essential to developing better diagnostics and therapeutics. Among the best-characterized tubular organs are the Drosophila salivary gland and trachea, organs whose relative simplicity have allowed for in depth analysis of gene function, yielding key mechanistic insight into tube initiation, remodeling and maintenance. Here, we review our current understanding of salivary gland and trachea formation - highlighting recent discoveries into how these organs attain their final form and function. Copyright © 2011 Wiley Periodicals, Inc.

Protein kinase C-ε activation induces mitochondrial dysfunction and fragmentation in renal proximal tubules

PubMed Central

Bakajsova, Diana; Samarel, Allen M.

2011-01-01

PKC-ε activation mediates protection from ischemia-reperfusion injury in the myocardium. Mitochondria are a subcellular target of these protective mechanisms of PKC-ε. Previously, we have shown that PKC-ε activation is involved in mitochondrial dysfunction in oxidant-injured renal proximal tubular cells (RPTC; Nowak G, Bakajsova D, Clifton GL Am J Physiol Renal Physiol 286: F307–F316, 2004). The goal of this study was to examine the role of PKC-ε activation in mitochondrial dysfunction and to identify mitochondrial targets of PKC-ε in RPTC. The constitutively active and inactive mutants of PKC-ε were overexpressed in primary cultures of RPTC using the adenoviral technique. Increases in active PKC-ε levels were accompanied by PKC-ε translocation to mitochondria. Sustained PKC-ε activation resulted in decreases in state 3 respiration, electron transport rate, ATP production, ATP content, and activities of complexes I and IV and F0F1-ATPase. Furthermore, PKC-ε activation increased mitochondrial membrane potential and oxidant production and induced mitochondrial fragmentation and RPTC death. Accumulation of the dynamin-related protein in mitochondria preceded mitochondrial fragmentation. Antioxidants blocked PKC-ε-induced increases in the oxidant production but did not prevent mitochondrial fragmentation and cell death. The inactive PKC-ε mutant had no effect on mitochondrial functions, morphology, oxidant production, and RPTC viability. We conclude that active PKC-ε targets complexes I and IV and F0F1-ATPase in RPTC. PKC-ε activation mediates mitochondrial dysfunction, hyperpolarization, and fragmentation. It also induces oxidant generation and cell death, but oxidative stress is not the mechanism of RPTC death. These results show that in contrast to protective effects of PKC-ε activation in cardiomyocytes, sustained PKC-ε activation is detrimental to mitochondrial function and viability in RPTC. PMID:21289057

Alkaline phosphatase protects against renal inflammation through dephosphorylation of lipopolysaccharide and adenosine triphosphate.

PubMed

Peters, E; Geraci, S; Heemskerk, S; Wilmer, M J; Bilos, A; Kraenzlin, B; Gretz, N; Pickkers, P; Masereeuw, R

2015-10-01

Recently, two phase-II trials demonstrated improved renal function in critically ill patients with sepsis-associated acute kidney injury treated with the enzyme alkaline phosphatase. Here, we elucidated the dual active effect on renal protection of alkaline phosphatase. The effect of human recombinant alkaline phosphatase (recAP) on LPS-induced renal injury was studied in Sprague-Dawley rats. Renal function was assessed by transcutaneous measurement of FITC-sinistrin elimination in freely moving, awake rats. The mechanism of action of recAP was further investigated in vitro using conditionally immortalized human proximal tubular epithelial cells (ciPTEC). In vivo, LPS administration significantly prolonged FITC-sinistrin half-life and increased fractional urea excretion, which was prevented by recAP co-administration. Moreover, recAP prevented LPS-induced increase in proximal tubule injury marker, kidney injury molecule-1 expression and excretion. In vitro, LPS-induced production of TNF-α, IL-6 and IL-8 was significantly attenuated by recAP. This effect was linked to dephosphorylation, as enzymatically inactive recAP had no effect on LPS-induced cytokine production. RecAP-mediated protection resulted in increased adenosine levels through dephosphorylation of LPS-induced extracellular ADP and ATP. Also, recAP attenuated LPS-induced increased expression of adenosine A2A receptor. However, the A2A receptor antagonist ZM-241385 did not diminish the effects of recAP. These results indicate that the ability of recAP to reduce renal inflammation may account for the beneficial effect observed in septic acute kidney injury patients, and that dephosphorylation of ATP and LPS are responsible for this protective effect. © 2015 The British Pharmacological Society.

Tamm-Horsfall protein translocates to the basolateral domain of thick ascending limbs, interstitium, and circulation during recovery from acute kidney injury

PubMed Central

McCracken, Ruth; Liu, Yan; Heitmeier, Monique R.; Bourgeois, Soline; Ryerse, Jan; Wu, Xue-Ru

2013-01-01

Tamm-Horsfall protein (THP) is a glycoprotein normally targeted to the apical membrane domain of the kidney's thick ascending limbs (TAL). We previously showed that THP of TAL confers protection to proximal tubules against acute kidney injury (AKI) via a possible cross talk between the two functionally distinct tubular segments. However, the extent, timing, specificity, and functional effects of basolateral translocation of THP during AKI remain unclear. Using an ischemia-reperfusion (IRI) model of murine AKI, we show here that, while THP expression in TAL is downregulated at the peak of injury, it is significantly upregulated 48 h after IRI. Confocal immunofluorescence and immunoelectron microscopy reveal a major redirection of THP during recovery from the apical membrane domain of TAL towards the basolateral domain, interstitium, and basal compartment of S3 segments. This corresponds with increased THP in the serum but not in the urine. The overall epithelial polarity of TAL cells does not change, as evidenced by correct apical targeting of Na+-K+-2Cl cotransporter (NKCC2) and basolateral targeting of Na+-K+-ATPase. Compared with the wild-type, THP−/− mice show a significantly delayed renal recovery after IRI, due possibly to reduced suppression by THP of proinflammatory cytokines and chemokines such as monocyte chemoattractant protein-1 during recovery. Taken together, our data suggest that THP redistribution in the TAL after AKI is a protein-specific event and its increased interstitial presence negatively regulates the evolving inflammatory signaling in neighboring proximal tubules, thereby enhancing kidney recovery. The increase of serum THP may be used as a prognostic biomarker for recovery from AKI. PMID:23389456

Robot-assisted "Santosh-Post Graduate Institute tubularized flap pyelovesicostomy" in a solitary functioning kidney with giant hydronephrosis: A minimally invasive salvage procedure.

PubMed

Kumar, Santosh; Singh, Shivanshu; Kumar, Navneet

2016-03-01

We describe a case of a solitary functioning kidney with giant hydronephrosis secondary to ureteropelvic junction obstruction in a young girl who underwent successful robot-assisted tubularized flap pyelovesicostomy. The aim of this report was to highlight the feasibility and efficacy of this technique in salvaging such renal moieties and to present a brief review of the surgical options available for the management of giant hydronephrosis.

Is tenofovir involved in hypophosphatemia and decrease of tubular phosphate reabsorption in HIV-positive adults?

PubMed

Badiou, Stéphanie; De Boever, Corinne Merle; Terrier, Nathalie; Baillat, Vincent; Cristol, Jean-Paul; Reynes, Jacques

2006-05-01

Tubulopathy with hypophosphatemia have been observed in HIV-positive patients receiving a tenofovir-containing regimen. However, the real incidence and prevalence of hypophosphatemia and their relation to tubular reabsorption disorders in tenofovir-treated patients remain uncertain. The aim of our study was to explore the effect of tenofovir on phosphatemia and on tubular phosphate reabsorption. In a first transversal study, 145 HIV-positive adults (44+/-9 years) receiving tenofovir 300 mg daily with a mean exposure of 11+/-9 months were included. In a second prospective study, 29 HIV-positive antiretroviral experienced adults (44+/-10 years) were evaluated before introduction of tenofovir 300 mg daily (M0) and at 3 months (M3) and 6 months (M6), thereafter. Phosphate, creatinine, glucose and protein levels were determined in plasma and urine. The ratio of maximal reabsorption capacity (TmPO4)/glomerular filtration rate (GFR) was determined by using the normogramm of Walton and Bijvoet. In the transversal study, 26% of patients had hypophosphatemia (<0.84 mmol/l) while 47% of patients had a decreased TmPO4/GFR (<0.8 mmol/l). In the prospective study, baseline prevalence of hypophosphatemia (<0.84 mmol/l) and decreased TmPO4/GFR (<0.8mmol/l) was 31 and 41%, respectively. Three and 6 months after starting tenofovir, there is no significant change in mean phosphate levels (M0:0.91 mmol/l, M3:0.97 mmol/l, M6:0.98 mmol/l) and mean TmPO4/GFR (M0:0.80 mmol/l, M3:0.88 mmol/l, M6:0.84 mmol/l). Moreover, prevalence of hypophosphatemia (M3:28%, M6:28%) and decreased TmPO4/GFR (M3:41%, M6:45%) remained stable. Hypophosphatemia linked to a decreased proximal tubular reabsorption was frequently observed in HIV-positive adults independently of the use of tenofovir. In this preliminary study, no worsening effect on phosphatemia and tubular phosphate reabsorption was observed 6 months after introduction of tenofovir in treatment experienced patients.

Lovastatin prevents cisplatin-induced activation of pro-apoptotic DNA damage response (DDR) of renal tubular epithelial cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krüger, Katharina; Ziegler, Verena; Hartmann, Christina

The platinating agent cisplatin (CisPt) is commonly used in the therapy of various types of solid tumors. The anticancer efficacy of CisPt largely depends on the formation of bivalent DNA intrastrand crosslinks, which stimulate mechanisms of the DNA damage response (DDR), thereby triggering checkpoint activation, gene expression and cell death. The clinically most relevant adverse effect associated with CisPt treatment is nephrotoxicity that results from damage to renal tubular epithelial cells. Here, we addressed the question whether the HMG-CoA-reductase inhibitor lovastatin affects the DDR of renal cells by employing rat renal proximal tubular epithelial (NRK-52E) cells as in vitro model.more » The data show that lovastatin has extensive inhibitory effects on CisPt-stimulated DDR of NRK-52E cells as reflected on the levels of phosphorylated ATM, Chk1, Chk2, p53 and Kap1. Mitigation of CisPt-induced DDR by lovastatin was independent of the formation of DNA damage as demonstrated by (i) the analysis of Pt-(GpG) intrastrand crosslink formation by Southwestern blot analyses and (ii) the generation of DNA strand breaks as analyzed on the level of nuclear γH2AX foci and employing the alkaline comet assay. Lovastatin protected NRK-52E cells from the cytotoxicity of high CisPt doses as shown by measuring cell viability, cellular impedance and flow cytometry-based analyses of cell death. Importantly, the statin also reduced the level of kidney DNA damage and apoptosis triggered by CisPt treatment of mice. The data show that the lipid-lowering drug lovastatin extensively counteracts pro-apoptotic signal mechanisms of the DDR of tubular epithelial cells following CisPt injury. - Highlights: • Lovastatin blocks ATM/ATR-regulated DDR of tubular cells following CisPt treatment. • Lovastatin attenuates CisPt-induced activation of protein kinase ATM in vitro. • Statin-mediated DDR inhibition is independent of initial DNA damage formation. • Statin-mediated blockage of CisPt-triggered DDR leads to cytoprotection. • Lovastatin attenuates CisPt-induced kidney DNA damage and apoptosis in vivo.« less

Are gadolinium-based contrast media nephrotoxic? A renal biopsy study.

PubMed

Akgun, Hulya; Gonlusen, Gulfiliz; Cartwright, Joiner; Suki, Wadi N; Truong, Luan D

2006-09-01

Gadolinium-based contrast media were originally introduced as alternatives to iodinated media for magnetic resonance imaging. Although originally thought to be nonnephrotoxic, gadolinium-based contrast media have recently been reported to be associated with acute renal failure; the mechanism and the underlying renal injury are not completely understood. We report what is, to our knowledge, the first renal biopsy in this context. A 56-year-old patient underwent 2 consecutive vascular imaging procedures in conjunction with gadolinium-based contrast medium administration. A few days later, the patient developed acute renal failure. A renal biopsy showed acute tubular cell injury including patchy tubular cell necrosis, tubular cell degeneration, and marked proliferation of tubular cells, together with mild interstitial edema and interstitial inflammation, but without significant glomerular or vascular changes. During supportive therapy, renal function was partially regained. This case emphasizes the potential nephrotoxicity of gadolinium-based contrast media and suggests that the nephrotoxicity is related to potentially reversible acute tubular cell injury.

Low molecular weight fucoidan and its fractions inhibit renal epithelial mesenchymal transition induced by TGF-β1 or FGF-2.

PubMed

Li, Xinpeng; Li, Xiaohong; Zhang, Quanbin; Zhao, Tingting

2017-12-01

We investigated the renal protective effects of low molecular weight fucoidan (LMWF) and its two fractions (F0.5 and F1.0), which were extracted from Laminaria japonica, on the epithelial-mesenchymal transition (EMT) induced by transforming growth factor beta 1 (TGF-β1) and fibroblast growth factor 2 (FGF-2) in HK-2 human renal proximal tubular cells. Cell morphology and EMT markers (fibronectin and alpha-smooth muscle actin) demonstrated that cells treated with TGF-β1 or FGF-2 developed EMT to a significant extent. Treatment with LMWF or its fractions markedly attenuated the EMT and decreased expression of the EMT markers. The F1.0 fraction, the sulfated fucan fraction, was found to be the main active component of LMWF, and heparanase (HPSE) was a key factor in renal tubular epithelial trans-differentiation. The F1.0 fraction inhibited elevated HPSE and matrix metallopeptidase 9 expression, thereby attenuating the progress of EMT. Copyright © 2017 Elsevier B.V. All rights reserved.

Parietal cells-new perspectives in glomerular disease.

PubMed

Miesen, Laura; Steenbergen, Eric; Smeets, Bart

2017-07-01

In normal glomeruli, parietal epithelial cells (PECs) line the inside of Bowman's capsule and form an inconspicuous sheet of flat epithelial cells in continuity with the proximal tubular epithelial cells (PTECs) at the urinary pole and with the podocytes at the vascular pole. PECs, PTECs and podocytes have a common mesenchymal origin and are the result of divergent differentiation during embryogenesis. Podocytes and PTECs are highly differentiated cells with well-established functions pertaining to the maintenance of the filtration barrier and transport, respectively. For PECs, no specific function other than a structural one has been known until recently. Possible important functions for PECs in the fate of the glomerulus in glomerular disease have now become apparent: (1) PECs may be involved in the replacement of lost podocytes; (2) PECs form the basis of extracapillary proliferative lesions and subsequent sclerosis in glomerular disease. In addition to the acknowledgement that PECs are crucial in glomerular disease, knowledge has been gained regarding the molecular processes driving the phenotypic changes and behavior of PECs. Understanding these molecular processes is important for the development of specific therapeutic approaches aimed at either stimulation of the regenerative function of PECs or inhibition of the pro-sclerotic action of PECs. In this review, we discuss recent advances pertaining to the role of PECs in glomerular regeneration and disease and address the major molecular processes involved.

Impact of thoracic surgery on esophageal motor function—Evaluation by high resolution manometry

PubMed Central

Kandulski, Arne; Malfertheiner, Peter; Riedel, Sandra; Zardo, Patrick; Hachenberg, Thomas; Schreiber, Jens

2017-01-01

Background Alteration of esophageal function is a potential risk factor for postoperative complications in thoracic surgery. This prospective study investigates esophageal motility and function during and after thoracic procedures via high resolution manometry (HRM) and impedance technology with spatiotemporal representation of pressure data. Methods Twelve consecutive patients eligible for elective thoracic surgery underwent preoperative and postoperative (48 hours and 7 days) esophageal HRM. Swallowing acts were carried out with 5 mL of water, 10 mL of water and 1 cm3 bread in physiological posture to evaluate distal contraction integral (DCI). Length and location of contractile integrity breaks were measured by investigators blinded to the form of surgical intervention. The impact of surgical procedures on esophageal motility was quantified according to current Chicago Classification (CC) criteria. Pre-, intra- and postoperative 24-hour multi-channel impedance pH–metry (MII-pH) was performed to further analyze gastroesophageal reflux patterns. Results All patients were investigated 48 hours prior to and 7 days after thoracic procedures, with a total of n=675 swallowing acts being included in our study. Increased motility patterns of the tubular esophagus occurred temporally 48 hours postoperatively. DCI 48 hours after surgery increased significantly (5 mL, P=0.049; solid, P=0.014) and returned to baseline values after seven days (5 mL, P=0.039; solid, P=0.039). Break length was significantly reduced 48 hours postoperatively, especially in the proximal esophageal segment (transition zone). Follow-up measurements after another week were comparable to preoperative baseline findings. The perioperative MII-pH measurement showed numerous artifacts caused by intubation and ventilation during surgery also with increasing short and frequent acidic reflux episodes. Conclusions Thoracic procedures cause a transient modulation of esophageal peristalsis with postoperative increased contractility of the tubular esophagus, presumably without affecting intraesophageal reflex arcs. Although limited by the number of patients, we can conclude on our data that postoperative esophageal hypomotility is unlikely to promote secondary pulmonary complications. PMID:28740669

Green Tea Polyphenols Stimulate Mitochondrial Biogenesis and Improve Renal Function after Chronic Cyclosporin A Treatment in Rats

PubMed Central

Rehman, Hasibur; Krishnasamy, Yasodha; Haque, Khujista; Lemasters, John J.; Schnellmann, Rick G.; Zhong, Zhi

2013-01-01

Our previous studies showed that an extract from Camellia sinenesis (green tea), which contains several polyphenols, attenuates nephrotoxicity caused by cyclosporine A (CsA). Since polyphenols are stimulators of mitochondrial biogenesis (MB), this study investigated whether stimulation of MB plays a role in green tea polyphenol protection against CsA renal toxicity. Rats were fed a powdered diet containing green tea polyphenolic extract (0.1%) starting 3 days prior to CsA treatment (25 mg/kg, i.g. daily for 3 weeks). CsA alone decreased renal nuclear DNA-encoded oxidative phosphorylation (OXPHOS) protein ATP synthase-β (AS-β) by 42%, mitochondrial DNA (mtDNA)-encoded OXPHOS protein NADH dehydrogenase-3 (ND3) by 87% and their associated mRNAs. Mitochondrial DNA copy number was also decreased by 78% by CsA. Immunohistochemical analysis showed decreased cytochrome c oxidase subunit IV (COX-IV), an OXPHOS protein, in tubular cells. Peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α, the master regulator of MB, and mitochondrial transcription factor-A (Tfam), the transcription factor that regulates mtDNA replication and transcription, were 42% and 90% lower, respectively, in the kidneys of CsA-treated than in untreated rats. These results indicate suppression of MB by chronic CsA treatment. Green tea polyphenols alone and following CsA increased AS-β, ND3, COX-IV, mtDNA copy number, PGC-1α mRNA and protein, decreased acetylated PGC-1α, and increased Tfam mRNA and protein. In association with suppressed MB, CsA increased serum creatinine, caused loss of brush border and dilatation of proximal tubules, tubular atrophy, vacuolization, apoptosis, calcification, and increased neutrophil gelatinase-associated lipocalin expression, leukocyte infiltration, and renal fibrosis. Green tea polyphenols markedly attenuated CsA-induced renal injury and improved renal function. Together, these results demonstrate that green tea polyphenols attenuate CsA-induced kidney injury, at least in part, through the stimulation of MB. PMID:23755172

Development of a Bioreactor to Culture Tissue Engineered Ureters Based on the Application of Tubular OPTIMAIX 3D Scaffolds.

PubMed

Seifarth, Volker; Gossmann, Matthias; Janke, Heinz Peter; Grosse, Joachim O; Becker, Christoph; Heschel, Ingo; Artmann, Gerhard M; Temiz Artmann, Aysegül

2015-01-01

Regenerative medicine, tissue engineering and biomedical research give hope to many patients who need bio-implants. Tissue engineering applications have already been developed based on bioreactors. Physiological ureter implants, however, do not still function sufficiently, as they represent tubular hollow structures with very specific cellular structures and alignments consisting of several cell types. The aim of this study was to a develop a new bioreactor system based on seamless, collagenous, tubular OPTIMAIX 3D prototype sponge as scaffold material for ex-vivo culturing of a tissue engineered ureter replacement for future urological applications. Particular emphasis was given to a great extent to mimic the physiological environment similar to the in vivo situation of a ureter. NIH-3T3 fibroblasts, C2C12, Urotsa and primary genitourinary tract cells were applied as co-cultures on the scaffold and the penetration of cells into the collagenous material was followed. By the end of this study, the bioreactor was functioning, physiological parameter as temperature and pH and the newly developed BIOREACTOR system is applicable to tubular scaffold materials with different lengths and diameters. The automatized incubation system worked reliably. The tubular OPTIMAIX 3D sponge was a suitable scaffold material for tissue engineering purposes and co-cultivation procedures. © 2015 S. Karger AG, Basel.

The histomorphological findings of kidneys after application of high dose and high-energy shock wave lithotripsy.

PubMed

Demir, Aslan; Türker, Polat; Bozkurt, Suheyla Uyar; İlker, Yalcin Nazmi

2015-01-01

In this animal study, we reviewed the histomorphological findings in rabbit kidneys after a high number of high-energy shock wave applications and observed if there were any cumulative effects after repeated sessions. We formed 2 groups, each consisting of 8 rabbits. Group 1 received 1 session and group 2 received 3 sessions of ESWL with a 7 day interval between sessions, consisting of 3500 beats to the left kidney and 5500 beats to the right kidney per session. The specimens of kidneys were examined histomorphologically after bilateral nephrectomy was performed. For statistical analysis, 4 groups of specimens were formed. The first and second groups received 1 session, 3500 and 5500 beats, respectively. The third and fourth groups received 3 sessions, at 3500 and 5500 beats per each session, respectively. The sections were evaluated under a light microscope to determine subcapsular thickening; subcapsular, intratubular and parenchymal hemorrhage; subcapsular, intersitital, perivascular and proximal ureteral fibrosis; paranchymal necrosis; tubular epithelial vacuolization; tubular atrophy; glomerular destruction and calcification. In histopathological examinations capsular thickening, subcapsular hematoma, tubuloepithelial vacuolisation, glomerular destruction, parenchymal hemorrhage, interstitial fibrosis, and perivascular fibrosis were observed in all groups. In statistical analysis, on the basis of perivascular fibrosis and tubular atrophy, there was a beats per session dependent increase of both. The detrimental effects from ESWL are dose dependent but not cumulative for up to 3 sessions. Histopathological experimental animal studies will aid in understanding local and maybe, by means of these local effects, systemic effects.

Transport of N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine, a metabolite of trichloroethylene, by mouse multidrug resistance associated protein 2 (Mrp2)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsirulnikov, Kirill; Abuladze, Natalia; Koag, Myong-Chul

2010-04-15

N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine (Ac-DCVC) and S-(1,2-dichlorovinyl)-L-cysteine (DCVC) are the glutathione conjugation pathway metabolites of a common industrial contaminant and potent nephrotoxicant trichloroethylene (TCE). Ac-DCVC and DCVC are accumulated in the renal proximal tubule where they may be secreted into the urine by an unknown apical transporter(s). In this study, we explored the hypothesis that the apical transport of Ac-DCVC and/or DCVC may be mediated by the multidrug resistance associated protein 2 (Mrp2, ABCC2), which is known to mediate proximal tubular apical ATP-dependent transport of glutathione and numerous xenobiotics and endogenous substances conjugated with glutathione. Transport experiments using membrane vesicles prepared from mousemore » proximal tubule derived cells expressing mouse Mrp2 utilizing ATPase assay and direct measurements of Ac-DCVC/DCVC using liquid chromatography/tandem mass-spectrometry (LC/MS/MS) demonstrated that mouse Mrp2 mediates ATP-dependent transport of Ac-DCVC. Expression of mouse Mrp2 antisense mRNA significantly inhibited the vectorial basolateral to apical transport of Ac-DCVC but not DCVC in mouse proximal tubule derived cells endogenously expressing mouse Mrp2. The results suggest that Mrp2 may be involved in the renal secretion of Ac-DCVC.« less

Inducible nitric oxide synthase and apoptosis in murine proximal tubule epithelial cells.

PubMed

Tiwari, Manish M; Messer, Kurt J; Mayeux, Philip R

2006-06-01

Since inducible nitric oxide synthase (iNOS) and proximal tubule injury are known to be critical determinants of lipopolysaccharide (LPS)-induced renal failure, the role of nitric oxide (NO) in proximal tubule cell apoptosis was examined. An 18-h treatment with a combination of LPS (5 microg/ml) and interferon-gamma (IFN-gamma, 100 units/ml) synergistically induced iNOS and produced a 20-fold increase in NO generation in the TKPTS murine proximal tubule cell line. NO generation by LPS + IFN-gamma was blocked by a specific iNOS blocker, L-N6-(1-iminoethyl)-lysine (L-NIL, 1 mM). To assess the role of iNOS-derived NO in proximal tubule cell apoptosis, annexin V- and propidium iodide-labeled cells were analyzed by flow cytometry. Neither the induction of iNOS nor its inhibition produced significant apoptotic cell death in TKPTS cells. Two exogenous NO donors were used to examine the role of NO more directly in proximal tubule apoptosis. Although both sodium nitroprusside (SNP), an iron-containing, nitrosonium cation donor, and S-nitroso-N-acetylpenicillamine (SNAP), a noniron-containing, NO generator, produced a concentration-dependent increase in NO generation, only SNP increased apoptotic cell death in TKPTS cells (5.9 +/- 0.7% in control cells vs. 21.6 +/- 3.8% in SNP [500 microM]-treated cells; n = 4-9; p < 0.01). SNP-mediated tubule cell apoptosis was not dependent on the activation of caspases or p53 but was possibly related to the generation of reactive oxygen species by SNP. Thus, in TKPTS cells induction of iNOS and generation of NO by LPS does not lead to tubular epithelial cell death.

SGLT2 mediates glucose reabsorption in the early proximal tubule.

PubMed

Vallon, Volker; Platt, Kenneth A; Cunard, Robyn; Schroth, Jana; Whaley, Jean; Thomson, Scott C; Koepsell, Hermann; Rieg, Timo

2011-01-01

Mutations in the gene encoding for the Na(+)-glucose co-transporter SGLT2 (SLC5A2) associate with familial renal glucosuria, but the role of SGLT2 in the kidney is incompletely understood. Here, we determined the localization of SGLT2 in the mouse kidney and generated and characterized SGLT2-deficient mice. In wild-type (WT) mice, immunohistochemistry localized SGLT2 to the brush border membrane of the early proximal tubule. Sglt2(-/-) mice had glucosuria, polyuria, and increased food and fluid intake without differences in plasma glucose concentrations, GFR, or urinary excretion of other proximal tubular substrates (including amino acids) compared with WT mice. SGLT2 deficiency did not associate with volume depletion, suggested by similar body weight, BP, and hematocrit; however, plasma renin concentrations were modestly higher and plasma aldosterone levels were lower in Sglt2(-/-) mice. Whole-kidney clearance studies showed that fractional glucose reabsorption was significantly lower in Sglt2(-/-) mice compared with WT mice and varied in Sglt2(-/-) mice between 10 and 60%, inversely with the amount of filtered glucose. Free-flow micropuncture revealed that for early proximal collections, 78 ± 6% of the filtered glucose was reabsorbed in WT mice compared with no reabsorption in Sglt2(-/-) mice. For late proximal collections, fractional glucose reabsorption was 93 ± 1% in WT and 21 ± 6% in Sglt2(-/-) mice, respectively. These results demonstrate that SGLT2 mediates glucose reabsorption in the early proximal tubule and most of the glucose reabsorption by the kidney, overall. This mouse model mimics and explains the glucosuric phenotype of individuals carrying SLC5A2 mutations.

Acquired proximal renal tubulopathy in dogs exposed to a common dried chicken treat: retrospective study of 108 cases (2007-2009).

PubMed

Thompson, M F; Fleeman, L M; Kessell, A E; Steenhard, L A; Foster, S F

2013-09-01

Proximal renal tubulopathy was reported in Australian dogs with markedly increased frequency from September 2007. Two veterinarian-completed surveys were launched in response to an increased incidence of acquired proximal renal tubulopathy in dogs. The selection criterion for inclusion was glucosuria with blood glucose < 10 mmol/L. Data collected included signalment, presenting signs, history of feeding treats, results of urinalysis and blood tests, treatment and time to resolution of clinical signs. A total of 108 affected dogs were studied. All had been fed the same brand of dried chicken treats, made in China, for a median of 12 weeks (range, 0.3-78 weeks). Small breeds (< 10 kg) accounted for 88% of cases. Common presenting signs included polyuria/polydipsia (76%), lethargy (73%), inappetence (65%) and vomiting (54%). Common biochemical findings included euglycaemia (74%; 71/96), hypoglycaemia (23%; 22/96), acidosis (77%; 20/26), hypokalaemia (45%; 38/84), hypophosphataemia (37%; 28/75) and azotaemia (27%; 23/85). In addition to discontinuation of treats, 64 dogs received medical treatment, including intravenous fluids (52%) and oral electrolyte, amino acid or vitamin supplements. Six dogs died or were euthanased. Two dogs were necropsied. Histopathological findings consisted of proximal tubular necrosis accompanied by regeneration. Time to resolution of clinical signs in 35 survivors available for follow-up was < 2 weeks (n = 8), 2-4 weeks (n = 2), 5-7 weeks (n = 5) and 2-6 months (n = 10). Of the 108 dogs with acquired proximal renal tubulopathy contemporaneous with chicken treat consumption, most survived but many required aggressive supportive care. The treats likely contained a toxin targeting the proximal renal tubules. Diet history and urinalysis were vital for diagnosis. © 2013 Australian Veterinary Association.

Azilsartan Improves Salt Sensitivity by Modulating the Proximal Tubular Na+-H+ Exchanger-3 in Mice.

PubMed

Hatanaka, Masaki; Kaimori, Jun-Ya; Yamamoto, Satoko; Matsui, Isao; Hamano, Takayuki; Takabatake, Yoshitsugu; Ecelbarger, Carolyn M; Takahara, Shiro; Isaka, Yoshitaka; Rakugi, Hiromi

2016-01-01

A potent angiotensin II type-1 receptor blocker, azilsartan, has been reported to reduce blood pressure more effectively than candesartan. Interestingly, azilsartan can also restore the circadian rhythm of blood pressure. We hypothesized that azilsartan could also improve salt sensitivity; thus, we examined the effect of azilsartan on sodium handling in renal tubules. Subtotal nephrectomized C57BL/6 mice received azilsartan (1.0 mg/kg/day), candesartan (0.3 mg/kg/day), or vehicle via the oral route in conjunction with a normal- (0.3%) or high-salt (8.0%) diet. Two weeks later, the azilsartan group showed significantly lower blood pressure during the light period than the candesartan and vehicle groups (azilsartan: 103.1 ± 1.0; candesartan: 111.7 ± 2.7; vehicle: 125.5 ± 2.5 mmHg; P < 0.05; azilsartan or candesartan vs. vehicle). The azilsartan group also showed higher urinary fractional excretion of sodium during the dark period than the candesartan and vehicle groups (azilsartan: 21.37 ± 3.69%; candesartan: 14.17 ± 1.42%; vehicle: 13.85 ± 5.30%; P < 0.05 azilsartan vs. candesartan or vehicle). A pressure-natriuresis curve demonstrated that azilsartan treatment restored salt sensitivity. Immunofluorescence and western blotting showed lower levels of Na+-H+ exchanger-3 (NHE3) protein (the major sodium transporter in renal proximal tubules) in the azilsartan group, but not in the candesartan or vehicle groups. However, azilsartan did not affect NHE3 transcription levels. Interestingly, we did not observe increased expression of downstream sodium transporters, which would have compensated for the increased flow of sodium and water due to non-absorption by NHE3. We also confirmed the mechanism stated above using cultured opossum kidney proximal tubular cells. Results revealed that a proteasomal inhibitor (but not a lysosomal inhibitor) blocked the azilsartan-induced decrease in NHE3 protein expression, suggesting that azilsartan increases NHE3 ubiquitination. In conclusion, azilsartan (but not candesartan) improved salt sensitivity possibly by decreasing NHE3 expression via ubiquitin-proteasomal degradation.

Azilsartan Improves Salt Sensitivity by Modulating the Proximal Tubular Na+-H+ Exchanger-3 in Mice

PubMed Central

Hatanaka, Masaki; Kaimori, Jun-Ya; Yamamoto, Satoko; Matsui, Isao; Hamano, Takayuki; Takabatake, Yoshitsugu; Ecelbarger, Carolyn M.; Takahara, Shiro; Isaka, Yoshitaka; Rakugi, Hiromi

2016-01-01

A potent angiotensin II type-1 receptor blocker, azilsartan, has been reported to reduce blood pressure more effectively than candesartan. Interestingly, azilsartan can also restore the circadian rhythm of blood pressure. We hypothesized that azilsartan could also improve salt sensitivity; thus, we examined the effect of azilsartan on sodium handling in renal tubules. Subtotal nephrectomized C57BL/6 mice received azilsartan (1.0 mg/kg/day), candesartan (0.3 mg/kg/day), or vehicle via the oral route in conjunction with a normal- (0.3%) or high-salt (8.0%) diet. Two weeks later, the azilsartan group showed significantly lower blood pressure during the light period than the candesartan and vehicle groups (azilsartan: 103.1 ± 1.0; candesartan: 111.7 ± 2.7; vehicle: 125.5 ± 2.5 mmHg; P < 0.05; azilsartan or candesartan vs. vehicle). The azilsartan group also showed higher urinary fractional excretion of sodium during the dark period than the candesartan and vehicle groups (azilsartan: 21.37 ± 3.69%; candesartan: 14.17 ± 1.42%; vehicle: 13.85 ± 5.30%; P < 0.05 azilsartan vs. candesartan or vehicle). A pressure—natriuresis curve demonstrated that azilsartan treatment restored salt sensitivity. Immunofluorescence and western blotting showed lower levels of Na+-H+ exchanger-3 (NHE3) protein (the major sodium transporter in renal proximal tubules) in the azilsartan group, but not in the candesartan or vehicle groups. However, azilsartan did not affect NHE3 transcription levels. Interestingly, we did not observe increased expression of downstream sodium transporters, which would have compensated for the increased flow of sodium and water due to non-absorption by NHE3. We also confirmed the mechanism stated above using cultured opossum kidney proximal tubular cells. Results revealed that a proteasomal inhibitor (but not a lysosomal inhibitor) blocked the azilsartan-induced decrease in NHE3 protein expression, suggesting that azilsartan increases NHE3 ubiquitination. In conclusion, azilsartan (but not candesartan) improved salt sensitivity possibly by decreasing NHE3 expression via ubiquitin—proteasomal degradation. PMID:26807585

Detection and measurement of tubulitis in renal allograft rejection

NASA Astrophysics Data System (ADS)

Hiller, John B.; Chen, Qi; Jin, Jesse S.; Wang, Yung; Yong, James L. C.

1997-04-01

Tubulitis is one of the most reliable signs of acute renal allograft rejection. It occurs when mononuclear cells are localized between the lining tubular epithelial cells with or without disruption of the tubular basement membrane. It has been found that tubulitis takes place predominantly in the regions of the distal convoluted tubules and the cortical collecting system. The image processing tasks are to find the tubule boundaries and to find the relative location of the lymphocytes and epithelial cells and tubule boundaries. The requirement for accuracy applies to determining the relative locations of the lymphocytes and the tubule boundaries. This paper will show how the different sizes and grey values of the lymphocytes and epithelial cells simplify their identification and location. Difficulties in finding the tubule boundaries image processing will be illustrated. It will be shown how proximate location of epithelial cells and the tubule boundary leads to distortion in determination of the calculated boundary. However, in tubulitis the lymphocytes and the tubule boundaries are proximate.In these cases the tubule boundary is adequately resolved and the image processing is satisfactory to determining relativity in location. An adaptive non-linear anisotropic diffusion process is presented for image filtering and segmentation. Multi-layer analysis is used to extract lymphocytes and tubulitis from images. This paper will discuss grading of tissue using the Banff system. The ability to use computer to use computer processing will be argued as obviating problems of reproducability of values for this classification. This paper will also feature discussion of alternative approaches to image processing and provide an assessment of their capability for improving the identification of the tubule boundaries.

4-Phenylbutyrate Inhibits Tunicamycin-Induced Acute Kidney Injury via CHOP/GADD153 Repression

PubMed Central

Carlisle, Rachel E.; Brimble, Elise; Werner, Kaitlyn E.; Cruz, Gaile L.; Ask, Kjetil; Ingram, Alistair J.; Dickhout, Jeffrey G.

2014-01-01

Different forms of acute kidney injury (AKI) have been associated with endoplasmic reticulum (ER) stress; these include AKI caused by acetaminophen, antibiotics, cisplatin, and radiocontrast. Tunicamycin (TM) is a nucleoside antibiotic known to induce ER stress and is a commonly used inducer of AKI. 4-phenylbutyrate (4-PBA) is an FDA approved substance used in children who suffer from urea cycle disorders. 4-PBA acts as an ER stress inhibitor by aiding in protein folding at the molecular level and preventing misfolded protein aggregation. The main objective of this study was to determine if 4-PBA could protect from AKI induced by ER stress, as typified by the TM-model, and what mechanism(s) of 4-PBA's action were responsible for protection. C57BL/6 mice were treated with saline, TM or TM plus 4-PBA. 4-PBA partially protected the anatomic segment most susceptible to damage, the outer medullary stripe, from TM-induced AKI. In vitro work showed that 4-PBA protected human proximal tubular cells from apoptosis and TM-induced CHOP expression, an ER stress inducible proapoptotic gene. Further, immunofluorescent staining in the animal model found similar protection by 4-PBA from CHOP nuclear translocation in the tubular epithelium of the medulla. This was accompanied by a reduction in apoptosis and GRP78 expression. CHOP−/− mice were protected from TM-induced AKI. The protective effects of 4-PBA extended to the ultrastructural integrity of proximal tubule cells in the outer medulla. When taken together, these results indicate that 4-PBA acts as an ER stress inhibitor, to partially protect the kidney from TM-induced AKI through the repression of ER stress-induced CHOP expression. PMID:24416259

Urinary cystatin C as a renal biomarker and its immunohistochemical localization in anti-GBM glomerulonephritis rats.

PubMed

Togashi, Yuko; Imura, Naoko; Miyamoto, Yohei

2013-11-01

The usefulness of urinary cystatin C for the early detection of renal damage in anti-glomerular basement membrane (GBM) glomerulonephritis rats was investigated and compared to other biomarkers (β2-microglobulin, calbindin, clusterin, epidermal growth factor (EGF), alpha-glutathione S-transferase (GST-α), mu-glutathione S-transferase (GST-μ), kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), osteopontin, tissue inhibitor of metalloprotease-1 (TIMP-1), and vascular endothelial growth factor (VEGF)). Urinary levels of cystatin C increased in anti-GBM glomerulonephritis rats, whereas the conventional markers, plasma creatinine and UN did not, demonstrating its usefulness for the early detection of renal damage associated with anti-GBM glomerulonephritis. As well as cystatin C, urinary β2-microglobulin, clusterin, GST-α, GST-μ, KIM-1, and NGAL also had the potential to detect renal damage associated with anti-GBM glomerulonephritis. Furthermore, the immunohistochemical localization of cystatin C in the kidney was examined. Cystatin C expression was mainly observed in the proximal renal tubules in anti-GBM glomerulonephritis rats, and its expression barely changed with the progression of glomerulonephritis. Cystatin C expression was also observed in the tubular lumen of the cortex and medulla when glomerulonephritis was marked, which was considered to be characteristic of renal damage. In conclusion, urinary cystatin C, β2-microglobulin, clusterin, GST-α, GST-μ, KIM-1, and NGAL could be useful biomarkers of renal damage in anti-GBM glomerulonephritis rats. Immunohistochemical cystatin C expression in the proximal renal tubules was barely changed by the progression of glomerulonephritis, but it was newly observed in the tubular lumen when renal damage was apparent. Crown Copyright © 2013. Published by Elsevier GmbH. All rights reserved.

Hydrogen sulfide inhibits high glucose-induced NADPH oxidase 4 expression and matrix increase by recruiting inducible nitric oxide synthase in kidney proximal tubular epithelial cells.

PubMed

Lee, Hak Joo; Lee, Doug Yoon; Mariappan, Meenalakshmi M; Feliers, Denis; Ghosh-Choudhury, Goutam; Abboud, Hanna E; Gorin, Yves; Kasinath, Balakuntalam S

2017-04-07

High-glucose increases NADPH oxidase 4 (NOX4) expression, reactive oxygen species generation, and matrix protein synthesis by inhibiting AMP-activated protein kinase (AMPK) in renal cells. Because hydrogen sulfide (H 2 S) inhibits high glucose-induced matrix protein increase by activating AMPK in renal cells, we examined whether H 2 S inhibits high glucose-induced expression of NOX4 and matrix protein and whether H 2 S and NO pathways are integrated. High glucose increased NOX4 expression and activity at 24 h in renal proximal tubular epithelial cells, which was inhibited by sodium hydrosulfide (NaHS), a source of H 2 S. High glucose decreased AMPK phosphorylation and activity, which was restored by NaHS. Compound C, an AMPK inhibitor, prevented NaHS inhibition of high glucose-induced NOX4 expression. NaHS inhibition of high glucose-induced NOX4 expression was abrogated by N (ω)-nitro-l-arginine methyl ester, an inhibitor of NOS. NaHS unexpectedly augmented the expression of inducible NOS (iNOS) but not endothelial NOS. iNOS siRNA and 1400W, a selective iNOS inhibitor, abolished the ameliorative effects of NaHS on high glucose-induced NOX4 expression, reactive oxygen species generation, and, matrix laminin expression. Thus, H 2 S recruits iNOS to generate NO to inhibit high glucose-induced NOX4 expression, oxidative stress, and matrix protein accumulation in renal epithelial cells; the two gasotransmitters H 2 S and NO and their interaction may serve as therapeutic targets in diabetic kidney disease. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

TGF-β1 stimulates movement of renal proximal tubular epithelial cells in a three-dimensional cell culture via an autocrine TGF-β2 production.

PubMed

Luo, Deyi; Guan, Qiunong; Wang, Kunjie; Nguan, Christopher Y C; Du, Caigan

2017-01-01

TGF-βs are multifunctional cytokines, but their roles in human renal homeostasis are not fully understood. This study investigated the role of TGF-β1 in the movement of human renal proximal tubular epithelial cells (PTECs) in a three-dimensional (3D) model. HKC-8 cells, a human PTEC line, were grown in a 3D collagen culture system. Cell movement was observed under a microscope. The gene expression was examined using PCR Arrays or qRT-PCR, and protein levels by Western blot. Here, we showed that the tight junction structure formed between adjacent cells of a HKC-8 cell colony in 3D cultures, and TGF-β1 stimulated their movement, evidenced by the appearance of fingerlike pseudopodia in the leader cells at the edge of the colonies. The cell movement of these human PTECs was correlated with up-regulation of both MMP2 and MMP9 and down-regulation or inactivation of PLAUR and PTK2B. Analysis of TGF-β signaling targets confirmed autocrine production of TGF-β2 and its cleaving enzyme furin as well as SNAI1 by TGF-β1stimulation. Knockdown of TGF-β2 expression disrupted TGF-β1-stimulated PTEC invasiveness, which was correlated with the down-regulation of MMP2 and MMP9. In conclusion, the activation of TGF-β receptor autocrine signaling by up-regulated TGF-β2 may play a pivotal role in TGF-β1-induced human PTEC movement, which could be mediated at least by both MMP2 and MMP9. Copyright © 2016 Elsevier Inc. All rights reserved.

Renal nerve stimulation leads to the activation of the Na+/H+ exchanger isoform 3 via angiotensin II type I receptor.

PubMed

Pontes, Roberto B; Crajoinas, Renato O; Nishi, Erika E; Oliveira-Sales, Elizabeth B; Girardi, Adriana C; Campos, Ruy R; Bergamaschi, Cássia T

2015-04-15

Renal nerve stimulation at a low frequency (below 2 Hz) causes water and sodium reabsorption via α1-adrenoreceptor tubular activation, a process independent of changes in systemic blood pressure, renal blood flow, or glomerular filtration rate. However, the underlying mechanism of the reabsorption of sodium is not fully understood. Since the sympathetic nervous system and intrarenal ANG II appear to act synergistically to mediate the process of sodium reabsorption, we hypothesized that low-frequency acute electrical stimulation of the renal nerve (ESRN) activates NHE3-mediated sodium reabsorption via ANG II AT1 receptor activation in Wistar rats. We found that ESRN significantly increased urinary angiotensinogen excretion and renal cortical ANG II content, but not the circulating angiotensinogen levels, and also decreased urinary flow and pH and sodium excretion via mechanisms independent of alterations in creatinine clearance. Urinary cAMP excretion was reduced, as was renal cortical PKA activity. ESRN significantly increased NHE3 activity and abundance in the apical microvillar domain of the proximal tubule, decreased the ratio of phosphorylated NHE3 at serine 552/total NHE3, but did not alter total cortical NHE3 abundance. All responses mediated by ESRN were completely abolished by a losartan-mediated AT1 receptor blockade. Taken together, our results demonstrate that higher NHE3-mediated proximal tubular sodium reabsorption induced by ESRN occurs via intrarenal renin angiotensin system activation and triggering of the AT1 receptor/inhibitory G-protein signaling pathway, which leads to inhibition of cAMP formation and reduction of PKA activity. Copyright © 2015 the American Physiological Society.

Overexpression of catalase prevents hypertension and tubulointerstitial fibrosis and normalization of renal angiotensin-converting enzyme-2 expression in Akita mice

PubMed Central

Shi, Yixuan; Lo, Chao-Sheng; Chenier, Isabelle; Maachi, Hasna; Filep, Janos G.; Ingelfinger, Julie R.; Zhang, Shao-Ling

2013-01-01

We investigated the relationship among oxidative stress, hypertension, renal injury, and angiotensin-converting enzyme-2 (ACE2) expression in type 1 diabetic Akita mice. Blood glucose, blood pressure, and albuminuria were monitored for up to 5 mo in adult male Akita and Akita catalase (Cat) transgenic (Tg) mice specifically overexpressing Cat, a key antioxidant enzyme in their renal proximal tubular cells (RPTCs). Same-age non-Akita littermates and Cat-Tg mice served as controls. In separate studies, adult male Akita mice (14 wk) were treated with ANG 1–7 (500 μg·kg−1·day−1 sc) ± A-779, an antagonist of the Mas receptor (10 mg·kg−1·day−1 sc), and euthanized at the age of 18 wk. The left kidneys were processed for histology and apoptosis studies. Renal proximal tubules were isolated from the right kidneys to assess protein and gene expression. Urinary angiotensinogen (AGT), angiotensin II (ANG II), and ANG 1–7 were quantified by specific ELISAs. Overexpression of Cat attenuated renal oxidative stress; prevented hypertension; normalized RPTC ACE2 expression and urinary ANG 1–7 levels (both were low in Akita mice); ameliorated glomerular filtration rate, albuminuria, kidney hypertrophy, tubulointerstitial fibrosis, and tubular apoptosis; and suppressed profibrotic and proapoptotic gene expression in RPTCs of Akita Cat-Tg mice compared with Akita mice. Furthermore, daily administration of ANG 1–7 normalized systemic hypertension in Akita mice, which was reversed by A-779. These data demonstrate that Cat overexpression prevents hypertension and progression of nephropathy and highlight the importance of intrarenal oxidative stress and ACE2 expression contributing to hypertension and renal injury in diabetes. PMID:23552863

Characterization of Polymyxin B Biodistribution and Disposition in an Animal Model

PubMed Central

Manchandani, Pooja; Zhou, Jian; Ledesma, Kimberly R.; Truong, Luan D.; Chow, Diana S.-L.; Eriksen, Jason L.

2015-01-01

Despite dose-limiting nephrotoxicity concerns, polymyxin B has resurged as the treatment of last resort for multidrug-resistant Gram-negative bacterial infections. However, the pharmacokinetic, pharmacodynamic, and nephrotoxic properties of polymyxin B still are not thoroughly understood. The objective of this study was to provide additional insights into the overall biodistribution and disposition of polymyxin B in an animal model. Sprague-Dawley rats were dosed with intravenous polymyxin B (3 mg/kg of body weight). Drug concentrations in the serum, urine, bile, and tissue (brain, heart, lungs, liver, spleen, kidneys, and skeletal muscle) samples over time were assayed by a validated methodology. Among all the organs evaluated, polymyxin B distribution was highest in the kidneys. The mean renal tissue/serum polymyxin B concentration ratios were 7.45 (95% confidence interval [CI], 4.63 to 10.27) at 3 h and 19.62 (95% CI, 5.02 to 34.22) at 6 h postdose. Intrarenal drug distribution was examined by immunostaining. Using a ratiometric analysis, proximal tubular cells showed the highest accumulation of polymyxin B (Mander's overlap coefficient, 0.998) among all cell types evaluated. Less than 5% of the administered dose was recovered in urine over 48 h, but all 4 major polymyxin B components were detected in the bile over 4 h. These findings corroborate previous results that polymyxin B is highly accumulated in the kidneys, but the elimination likely is via a nonrenal route. Biliary excretion could be one of the routes of polymyxin B elimination, and this should be further explored. The elucidation of mechanism(s) of drug uptake in proximal tubular cells is ongoing. PMID:26643340

Acute lethal toxicity, hyperkalemia associated with renal injury and hepatic damage after intravenous administration of cadmium nitrate in rats.

PubMed

Dote, Emi; Dote, Tomotaro; Shimizu, Hiroyasu; Shimbo, Yukari; Fujihara, Michiko; Kono, Koichi

2007-01-01

Cadmium nitrate Cd(NO(3))(2) (CdN) is commonly used in Ni-Cd battery factories. The possibility of accidental exposure to CdN is great. CdN is very soluble in water compared to other Cd compounds. Therefore, acute toxicity would be expected to be quick due to rapid absorption after exposure. However, the mechanisms of CdN toxicity have not been fully elucidated. We investigated the acute lethal toxicity and harmful systemic effects of acute exposure to large doses of CdN. The lethal dose and dose-response study of the liver and kidney were determined after intravenous administration of CdN in rats. The LD(50) of CdN was determined to be 5.5 mg/kg. Doses of 2.1, 4.2, 6.3 mg/kg were selected for the dose-response study. Liver injury was induced at doses greater than 4.2 mg/kg. Severe hepatic injury occurred in the 6.3 mg/kg group, which would have been caused by acute exposure to the high concentration of Cd that exceeded the critical concentration in hepatic tissue. A remarkable decrease in urine volume in the 6.3 mg/kg group indicated acute renal failure. A decrease in creatinine clearance suggested acute glomerular dysfunction at doses greater than 4.2 mg/kg. Increases in urinary N-acetyl-beta-D-glucosaminidase/creatinine, beta(2)-microglobulin and glucose in the 6.3 mg/kg group indicated proximal tubular injury. Secretion of K ion was also severely affected by proximal tubular injury and severe decreases in urine volume, and an increase in serum K ion was identified at doses greater than 4.2 mg/kg. Thus severe hyperkalemia might be associated with the cardiac-derived lethal toxicity of CdN.

Quercetin protects against radiocontrast medium toxicity in human renal proximal tubular cells.

PubMed

Andreucci, Michele; Faga, Teresa; Pisani, Antonio; Serra, Raffaele; Russo, Domenico; De Sarro, Giovambattista; Michael, Ashour

2018-05-01

Radiocontrast media (RCM)-induced acute kidney injury (CI-AKI) is a major clinical problem whose pathophysiology is not well understood. Direct toxic effects on renal cells, possibly mediated by reactive oxygen species, have been postulated as contributing to CI-AKI. We investigated the effect of quercetin on human renal proximal tubular (HK-2) cells treated with the radiocontrast medium (RCM) sodium diatrizoate. Quercetin is the most widely studied flavonoid, and the most abundant flavonol present in foods. It has been suggested to have many health benefits, including angioprotective properties and anti-cancer effects. These beneficial effects have been attributed to its antioxidant properties and its ability to modulate cell signaling pathways. Incubation of HK-2 cells with 100 μM quercetin caused a decrease in cell viability and pre-treatment of HK-2 cells with 100 μM quercetin followed by incubation with 75 mgI/ml sodium diatrizoate for 2 hr caused a decrease in cell viability which was worse than in cells treated with diatrizoate alone. However, further incubation of the cells (for 22 hr) after removal of the diatrizoate and quercetin caused a recovery in cell viability in those cells previously treated with quercetin + diatrizoate and quercetin alone. Analysis of signaling molecules by Western blotting showed that in RCM-treated cells receiving initial pre-treatment with quercetin, followed by its removal, an increase in phosphorylation of Akt (Ser473), pSTAT3 (Tyr705), and FoxO3a (Thr32) as well as an induction of Pim-1 and decrease in PARP1 cleavage were observed. Quercetin may alleviate the longer-term toxic effects of RCM toxicity and its possible beneficial effects should be further investigated. © 2017 Wiley Periodicals, Inc.

Microparticles released by vascular endothelial cells increase hypoxia inducible factor expression in human proximal tubular HK-2 cells.

PubMed

Fernandez-Martínez, Ana Belen; Torija, Ana Valdehita; Carracedo, Julia; Ramirez, Rafael; de Lucio-Cazaña, Francisco Javier

2014-08-01

Microparticles are produced by vesiculation of the cell plasma membrane and serve as vectors of cell-to-cell communication. Co-culture experiments have shown that hypoxia-inducible factor-α (HIF-α)-regulated-genes are up-regulated in human renal proximal tubular HK-2 cells by endothelial cell factors which might be transported inside endothelial microparticles (EMP). Here we aimed to study in HK-2 cells the effect of EMP, produced by activated endothelial cells, on HIF-α and HIF-α-regulated vascular endothelial growth factor-A (VEGF-A). EMP, at a concentration much lower than that found in plasma, increased the expression of HIF-α/VEGF-A in a COX-2/EP2 receptor dependent manner. Since the EMP/cells ratio was ∼1/1000, we hypothesized that paracrine mediators produced by HK-2 cells amplified the initial signal. This hypothesis was confirmed by two facts which also suggested that the mediators were conveyed by particles released by HK-2 cells: (i) HIF-α was up-regulated in HK-2 cells treated with the pellet obtained from the conditioned medium of the EMP-treated HK-2 cells. (ii) In transwell experiments, EMP-treated cells increased the expression of HIF-α in untreated HK-2 cells. Interestingly, we detected these cells, particles that were released by EMP-treated HK-2 cells. Depending on the pathological context, activation of HIF-α and VEGF-A signaling in renal tissue/cells may have either beneficial or harmful effects. Therefore, our results suggest that their presence in the urinary space of EMP produced by activated endothelial cells may influence the outcome of a number of renal diseases. Copyright © 2014 Elsevier Ltd. All rights reserved.

Inhibiting post-translational core fucosylation protects against albumin-induced proximal tubular epithelial cell injury.

PubMed

Wang, Dapeng; Fang, Ming; Shen, Nan; Li, Longkai; Wang, Weidong; Wang, Lingyu; Lin, Hongli

2017-01-01

Albuminuria is an independent risk factor for renal interstitial fibrosis (RIF). Glomerular-filtered albumin in endocytic and non-endocytic pathways may injure proximal tubular epithelial cells (PTECs) via megalin and TGFβRII, respectively. Since megalin and TGFβRII are both modified by post-translational core fucosylation, which plays a critical role in RIF. Thus, we sought to identify whether core fucosylation is a potential target for reducing albumin-induced injury to PTECs. We constructed a human PTEC-derived cell line (HK-2 cells) and established an in vitro model of bovine serum albumin (BSA) injury. RNAi was used to inhibit the expression of megalin, TGFβRII, and Fut8. Western blotting, immunostaining, ELISA, lectin blotting, and fluorescence-activated cell sorting were used to identify BSA-induced endocytic and non-endocytic damage in HK-2 cells. Fut8 is a core fucosylation-related gene, which is significantly increased in HK-2 cells following an incubation with BSA. Fut8 siRNA significantly reduced the core fucosylation of megalin and TGFβRII and also inhibited the activation of the TGFβ/TGFβRII/Smad2/3 signaling pathway. Furthermore, Fut8 siRNA could reduce monocyte chemotactic protein-1, reactive oxygen species, and apoptosis, as well as significantly decrease the fibronectin and collagen I levels in BSA-overloaded HK-2 cells. Core fucosylation inhibition was more effective than inhibiting either megalin or TGFβRII for the prevention of albumin-induced injury to PTECs. Our findings indicate that post-translational core fucosylation is essential for the albumin-induced injury to PTECs. Thus, the inhibition of core fucosylation could effectively alleviate albumin-induced endocytic and non-endocytic injury to PTECs. Our study provides a potential therapeutic target for albuminuria-induced injury.

Recombinant erythropoietin acutely decreases renal perfusion and decouples the renin-angiotensin-aldosterone system.

PubMed

Aachmann-Andersen, Niels J; Christensen, Soren J; Lisbjerg, Kristian; Oturai, Peter; Johansson, Pär I; Holstein-Rathlou, Niels-Henrik; Olsen, Niels V

2018-03-01

The effect of recombinant erythropoietin (rhEPO) on renal and systemic hemodynamics was evaluated in a randomized double-blinded, cross-over study. Sixteen healthy subjects were tested with placebo, or low-dose rhEPO for 2 weeks, or high-dose rhEPO for 3 days. Subjects refrained from excessive salt intake, according to instructions from a dietitian. Renal clearance studies were done for measurements of renal plasma flow, glomerular filtration rate (GFR) and the segmentel tubular handling of sodium and water (lithium clearance). rhEPO increased arterial blood pressure, total peripheral resistance, and renal vascular resistance, and decreased renal plasma flow in the high-dose rhEPO intervention and tended to decrease GFR. In spite of the decrease in renal perfusion, rhEPO tended to decrease reabsorption of sodium and water in the proximal tubule and induced a prompt decrease in circulating levels of renin and aldosterone, independent of changes in red blood cell mass, blood volumes, and blood pressure. We also found changes in biomarkers showing evidence that rhEPO induced a prothrombotic state. Our results suggest that rhEPO causes a direct downregulation in proximal tubular reabsorption that seems to decouple the activity of the renin-angiotensin-aldosterone system from changes in renal hemodynamics. This may serve as a negative feed-back mechanism on endogenous synthesis of EPO when circulating levels of EPO are high. These results demonstrates for the first time in humans a direct effect of rhEPO on renal hemodynamics and a decoupling of the renin-angiotensin-aldosterone system. © 2018 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Selenium-binding protein 1: a sensitive urinary biomarker to detect heavy metal-induced nephrotoxicity.

PubMed

Lee, Eui Kyung; Shin, Young-Jun; Park, Eun Young; Kim, Nam Deuk; Moon, Aree; Kwack, Seung Jun; Son, Ji Yeon; Kacew, Sam; Lee, Byung Mu; Bae, Ok-Nam; Kim, Hyung Sik

2017-04-01

Identifying novel biomarkers to detect nephrotoxicity is clinically important. Here, we attempted to identify new biomarkers for mercury-induced nephrotoxicity and compared their sensitivity to that of traditional biomarkers in animal models. Comparative proteomics analysis was performed in kidney tissues of Sprague-Dawley rats after oral treatment with HgCl 2 (0.1, 1, or 5 mg/kg/day) for 21 days. Kidney cortex tissues were analyzed by two-dimensional gel electrophoresis/matrix-assisted laser desorption/ionization, and differentially expressed proteins were identified. The corresponding spots were quantitated by RT-PCR. Selenium-binding protein 1 (SBP1) was found to be the most markedly upregulated protein in the kidney cortex of rats after HgCl 2 administration. However, blood urea nitrogen, serum creatinine, and glucose levels increased significantly only in the 1 or 5 mg/kg HgCl 2 -treated groups. A number of urinary excretion proteins, including kidney injury molecule-1, clusterin, monocyte chemoattractant protein-1, and β-microglobulin, increased dose-dependently. Histopathological examination revealed severe proximal tubular damage in high-dose (5 mg/kg) HgCl 2 -exposed groups. In addition, urinary excretion of SBP1 significantly increased in a dose-dependent manner. To confirm the critical role of SBP1 as a biomarker for nephrotoxicity, normal kidney proximal tubular cells were treated with HgCl 2 , CdCl 2 , or cisplatin for 24 h. SBP1 levels significantly increased in conditioned media exposed to nephrotoxicants, but decreased in cell lysates. Our investigations suggest that SBP1 may play a critical role in the pathological processes underlying chemical-induced nephrotoxicity. Thus, urinary excretion of SBP1 might be a sensitive and specific biomarker to detect early stages of kidney injury.

High glucose augments angiotensinogen in human renal proximal tubular cells through hepatocyte nuclear factor-5

PubMed Central

Wang, Juan; Shibayama, Yuki; Kobori, Hiroyuki; Liu, Ya; Kobara, Hideki; Masaki, Tsutomu; Wang, Zhiyu

2017-01-01

High glucose has been demonstrated to induce angiotensinogen (AGT) synthesis in the renal proximal tubular cells (RPTCs) of rats, which may further activate the intrarenal renin-angiotensin system (RAS) and contribute to diabetic nephropathy. This study aimed to investigate the effects of high glucose on AGT in the RPTCs of human origin and identify the glucose-responsive transcriptional factor(s) that bind(s) to the DNA sequences of AGT promoter in human RPTCs. Human kidney (HK)-2 cells were treated with normal glucose (5.5 mM) and high glucose (15.0 mM), respectively. Levels of AGT mRNA and AGT secretion of HK-2 cells were measured by real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. Consecutive 5’-end deletion mutant constructs and different site-directed mutagenesis products of human AGT promoter sequences were respectively transfected into HK-2 cells, followed by AGT promoter activity measurement through dual luciferase assay. High glucose significantly augmented the levels of AGT mRNA and AGT secretion of HK-2 cells, compared with normal glucose treatment. High glucose also significantly augmented AGT promoter activity in HK-2 cells transfected with the constructs of human AGT promoter sequences, compared with normal glucose treatment. Hepatocyte nuclear factor (HNF)-5 was found to be one of the glucose-responsive transcriptional factors of AGT in human RPTCs, since the mutation of its binding sites within AGT promoter sequences abolished the above effects of high glucose on AGT promoter activity as well as levels of AGT mRNA and its secretion. The present study has demonstrated, for the first time, that high glucose augments AGT in human RPTCs through HNF-5, which provides a potential therapeutic target for diabetic nephropathy. PMID:29053707

Effects of a Single Dose of Parecoxib on Inflammatory Response and Ischemic Tubular Injury Caused by Hemorrhagic Shock in Rats.

PubMed

Takaku, Mariana; da Silva, Andre Carnevali; Iritsu, Nathalie Izumi; Vianna, Pedro Thadeu Galvao; Castiglia, Yara Marcondes Machado

2018-01-01

Parecoxib, a selective COX-2 inhibitor, is used to improve analgesia in postoperative procedures. Here we evaluated whether pretreatment with a single dose of parecoxib affects the function, cell injury, and inflammatory response of the kidney of rats subjected to acute hemorrhage. Inflammatory response was determined according to serum and renal tissue cytokine levels (IL-1 α , IL-1 β , IL-6, IL-10, and TNF- α ). Forty-four adult Wistar rats anesthetized with sevoflurane were randomized into four groups: placebo/no hemorrhage (Plc/NH); parecoxib/no hemorrhage (Pcx/NH); placebo/hemorrhage (Plc/H); and parecoxib/hemorrhage (Pcx/H). Pcx groups received a single dose of intravenous parecoxib while Plc groups received a single dose of placebo (isotonic saline). Animals in hemorrhage groups underwent bleeding of 30% of blood volume. Renal function and renal histology were then evaluated. Plc/H showed the highest serum levels of cytokines, suggesting that pretreatment with parecoxib reduced the inflammatory response in rats subjected to hemorrhage. No difference in tissue cytokine levels between groups was observed. Plc/H showed higher percentage of tubular dilation and degeneration, indicating that parecoxib inhibited tubular injury resulting from renal hypoperfusion. Our findings indicate that pretreatment with a single dose of parecoxib reduced the inflammatory response and tubular renal injury without altering renal function in rats undergoing acute hemorrhage.

Time course of pathogenic and adaptation mechanisms in cystinotic mouse kidneys.

PubMed

Gaide Chevronnay, Héloïse P; Janssens, Virginie; Van Der Smissen, Patrick; N'Kuli, Francisca; Nevo, Nathalie; Guiot, Yves; Levtchenko, Elena; Marbaix, Etienne; Pierreux, Christophe E; Cherqui, Stéphanie; Antignac, Corinne; Courtoy, Pierre J

2014-06-01

Cystinosis, a main cause of Fanconi syndrome, is reproduced in congenic C57BL/6 cystinosin knockout (KO) mice. To identify the sequence of pathogenic and adaptation mechanisms of nephropathic cystinosis, we defined the onset of Fanconi syndrome in KO mice between 3 and 6 months of age and analyzed the correlation with structural and functional changes in proximal tubular cells (PTCs), with focus on endocytosis of ultrafiltrated disulfide-rich proteins as a key source of cystine. Despite considerable variation between mice at the same age, typical event sequences were delineated. At the cellular level, amorphous lysosomal inclusions preceded cystine crystals and eventual atrophy without crystals. At the nephron level, lesions started at the glomerulotubular junction and then extended distally. In situ hybridization and immunofluorescence revealed progressive loss of expression of megalin, cubilin, sodium-glucose cotransporter 2, and type IIa sodium-dependent phosphate cotransporter, suggesting apical dedifferentiation accounting for Fanconi syndrome before atrophy. Injection of labeled proteins revealed that defective endocytosis in S1 PTCs led to partial compensatory uptake by S3 PTCs, suggesting displacement of endocytic load and injury by disulfide-rich cargo. Increased PTC apoptosis allowed luminal shedding of cystine crystals and was partially compensated for by tubular proliferation. We conclude that lysosomal storage triggered by soluble cystine accumulation induces apical PTC dedifferentiation, which causes transfer of the harmful load of disulfide-rich proteins to more distal cells, possibly explaining longitudinal progression of swan-neck lesions. Furthermore, our results suggest that subsequent adaptation mechanisms include lysosomal clearance of free and crystalline cystine into urine and ongoing tissue repair. Copyright © 2014 by the American Society of Nephrology.

Mitochondrial DNA polymerase editing mutation, PolgD257A, reduces the diabetic phenotype of Akita male mice by suppressing appetite.

PubMed

Fox, Raymond; Kim, Hyung-Suk; Reddick, Robert L; Kujoth, Gregory C; Prolla, Tomas A; Tsutsumi, Shuichi; Wada, Youichiro; Smithies, Oliver; Maeda, Nobuyo

2011-05-24

Diabetes and the development of its complications have been associated with mitochondrial DNA (mtDNA) dysfunction, but causal relationships remain undetermined. With the objective of testing whether increased mtDNA mutations exacerbate the diabetic phenotype, we have compared mice heterozygous for the Akita diabetogenic mutation (Akita) with mice homozygous for the D257A mutation in mitochondrial DNA polymerase gamma (Polg) or with mice having both mutations (Polg-Akita). The Polg-D257A protein is defective in proofreading and increases mtDNA mutations. At 3 mo of age, the Polg-Akita and Akita male mice were equally hyperglycemic. Unexpectedly, as the Polg-Akita males aged to 9 mo, their diabetic symptoms decreased. Thus, their hyperglycemia, hyperphagia and urine output declined significantly. The decrease in their food intake was accompanied by increased plasma leptin and decreased plasma ghrelin, while hypothalamic expression of the orexic gene, neuropeptide Y, was lower and expression of the anorexic gene, proopiomelanocortin, was higher. Testis function progressively worsened with age in the double mutants, and plasma testosterone levels in 9-mo-old Polg-Akita males were significantly reduced compared with Akita males. The hyperglycemia and hyperphagia returned in aged Polg-Akita males after testosterone administration. Hyperglycemia-associated distal tubular damage in the kidney also returned, and Polg-D257A-associated proximal tubular damage was enhanced. The mild diabetes of female Akita mice was not affected by the Polg-D257A mutation. We conclude that reduced diabetic symptoms of aging Polg-Akita males results from appetite suppression triggered by decreased testosterone associated with damage to the Leydig cells of the testis.

Sodium-potassium-adenosinetriphosphatase-dependent sodium transport in the kidney: hormonal control.

PubMed

Féraille, E; Doucet, A

2001-01-01

Tubular reabsorption of filtered sodium is quantitatively the main contribution of kidneys to salt and water homeostasis. The transcellular reabsorption of sodium proceeds by a two-step mechanism: Na(+)-K(+)-ATPase-energized basolateral active extrusion of sodium permits passive apical entry through various sodium transport systems. In the past 15 years, most of the renal sodium transport systems (Na(+)-K(+)-ATPase, channels, cotransporters, and exchangers) have been characterized at a molecular level. Coupled to the methods developed during the 1965-1985 decades to circumvent kidney heterogeneity and analyze sodium transport at the level of single nephron segments, cloning of the transporters allowed us to move our understanding of hormone regulation of sodium transport from a cellular to a molecular level. The main purpose of this review is to analyze how molecular events at the transporter level account for the physiological changes in tubular handling of sodium promoted by hormones. In recent years, it also became obvious that intracellular signaling pathways interacted with each other, leading to synergisms or antagonisms. A second aim of this review is therefore to analyze the integrated network of signaling pathways underlying hormone action. Given the central role of Na(+)-K(+)-ATPase in sodium reabsorption, the first part of this review focuses on its structural and functional properties, with a special mention of the specificity of Na(+)-K(+)-ATPase expressed in renal tubule. In a second part, the general mechanisms of hormone signaling are briefly introduced before a more detailed discussion of the nephron segment-specific expression of hormone receptors and signaling pathways. The three following parts integrate the molecular and physiological aspects of the hormonal regulation of sodium transport processes in three nephron segments: the proximal tubule, the thick ascending limb of Henle's loop, and the collecting duct.

Fanconi's syndrome and nephrogenic diabetes insipidus in an adult treated with ifosfamide.

PubMed

Ingemi, Amanda I; Bota, Vasile M; Peguero, Anyeri; Charpentier, Margaret

2012-01-01

Fanconi's syndrome is a serious condition characterized by type II proximal renal tubular dysfunction, with urinary loss of glucose, amino acids, phosphate, bicarbonate, and potassium. Ifosfamide-induced Fanconi's syndrome is reported in about 1.4-5% of children being treated for solid tumors, yet only a few cases have been reported in adults. We describe a 54-year-old man who came to the hospital with symptoms of neutropenic fever 4 days after his fourth cycle of ifosfamide and doxorubicin treatment for recurrent sarcoma with metastases to the lung. During admission, he was noted to have severe renal tubular dysfunction; ifosfamide-induced nephrogenic diabetes insipidus and Fanconi's syndrome were suspected. He received supportive therapy that resulted in incomplete resolution of signs and symptoms. The patient was discharged after a 5-day hospital stay when his white blood cell count increased from 0.1-2.5 × 10(3) /mm(3) and his fever had resolved. Use of the Naranjo adverse drug reaction probability scale indicated a probable relationship (score of 7) between the patient's development of diabetes insipidus and Fanconi's syndrome and his use of ifosfamide. This dual diagnosis of diabetes insipidus and Fanconi's syndrome in an adult makes this case unusual, as well as therapeutically challenging. We conducted a review of the existing literature regarding ifosfamide-induced Fanconi's syndrome and describe the proposed mechanisms and therapeutic options. This case suggests that patients treated with ifosfamide should be monitored closely for renal function to identify, and perhaps prevent, these rare adverse events. Preliminary animal models show promise for adding N-acetylcysteine to ifosfamide treatment, but more research is necessary before using this drug as a therapeutic option. © 2012 Pharmacotherapy Publications, Inc.

A 90-day continuous vapor inhalation toxicity study of JP-8 jet fuel followed by 20 or 21 months of recovery in Fischer 344 rats and C57BL/6 mice.

PubMed

Mattie, D R; Alden, C L; Newell, T K; Gaworski, C L; Flemming, C D

1991-01-01

The kerosene-type jet fuel, JP-8, consists of a complex mixture of aliphatic and aromatic hydrocarbons. Because of the utility of JP-8, studies have been conducted to identify the potential long-term consequence of occupational inhalation exposure. Fischer 344 rats and C57BL/6 mice of both sexes were exposed to JP-8 vapors at 0, 500, and 1,000 mg/m3 on a continuous basis for 90 days, then followed by recovery until approximately 24 months of age. Occurrence of necrotizing dermatitis associated with fighting resulted in an increase in mortality in mice (male greater than female) during the 2 week to 9 month post-exposure recovery period. The male rat kidney developed a reversible ultrastructural increase in size and propensity for crystalloid changes of phagolysosomal proteinic reabsorption droplets in the proximal convoluted tubular epithelium. A specific triad of persisting light microscopic renal lesions occurred but functional change was limited to a decrease in urine concentration compared to controls that persisted throughout the recovery period. The response is comparable to the chronic effect of lifetime exposure of the male rat to unleaded gasoline, d-limonene, and p-dichlorobenzene, except for the absence of tubular tumorigenesis. The active toxicologic response presumably must occur over a greater proportion of the male rat's life span for the tumor component of this male rat hydrocarbon nephropathy syndrome. The predictiveness for humans must be questioned, since the pathologic response to JP-8 involved only one tissue in one sex of one species, and since the male rat response appears to be linked to an inherent renal protein peculiarity.

Berberine protects HK-2 cells from hypoxia/reoxygenation induced apoptosis via inhibiting SPHK1 expression.

PubMed

Lu, Jianrao; Yi, Yang; Pan, Ronghua; Zhang, Chuanfu; Han, Haiyan; Chen, Jie; Liu, Wenrui

2018-03-01

Renal ischemia reperfusion injury (RIRI) refers to the irreversible damage for renal function when blood perfusion is recovered after ischemia for an extended period, which is common in clinical surgeries and has been regarded as a major risk for acute renal failures (ARF) that is accompanied with unimaginably high morbidity and mortality. Hypoxia during ischemia followed by reoxygenation via reperfusion serves as a major event contributing to cell apoptosis, which has been widely accepted as the vital pathogenesis in RIRI. Preventing apoptosis in renal tubular epithelial cell has been considered as effective method for blocking RIRI. In this paper, we established a hypoxia/reoxygenation (H/R) injury model in human proximal tubular epithelial HK-2 cells. Here, we found increased SPHK1 levels in H/R injured HK-2 cells, which could be significantly down regulated after berberine treatment. Berberine has been reported to exert a protective effect on H/R-induced apoptosis of HK-2 cells. So, in our present study, we planned to investigate whether SPHK1 participated in the anti-apoptosis process of berberine in H/R injured HK-2 cells. Our study confirmed the protective effect of berberine against H/R-induced apoptosis in HK-2 cells through promoting cells viability, inhibiting cells apoptosis, and down-regulating p-P38, caspase-3, caspase-9 as well as SPHK1, while up regulating the ratio of Bcl-2/Bax. However, SPHK1 overexpression in HK-2 cells induced severe apoptosis, which can be significantly ameliorated with additional berberine treatment. We concluded that berberine could remarkably prevent H/R-induced apoptosis in HK-2 cells through down-regulating SPHK1 expression levels, and the mechanisms included the suppression of p38 MAPK activation and mitochondrial stress pathways.

Human Sodium Phosphate Transporter 4 (hNPT4/SLC17A3) as a Common Renal Secretory Pathway for Drugs and Urate*

PubMed Central

Jutabha, Promsuk; Anzai, Naohiko; Kitamura, Kenichiro; Taniguchi, Atsuo; Kaneko, Shuji; Yan, Kunimasa; Yamada, Hideomi; Shimada, Hidetaka; Kimura, Toru; Katada, Tomohisa; Fukutomi, Toshiyuki; Tomita, Kimio; Urano, Wako; Yamanaka, Hisashi; Seki, George; Fujita, Toshiro; Moriyama, Yoshinori; Yamada, Akira; Uchida, Shunya; Wempe, Michael F.; Endou, Hitoshi; Sakurai, Hiroyuki

2010-01-01

The evolutionary loss of hepatic urate oxidase (uricase) has resulted in humans with elevated serum uric acid (urate). Uricase loss may have been beneficial to early primate survival. However, an elevated serum urate has predisposed man to hyperuricemia, a metabolic disturbance leading to gout, hypertension, and various cardiovascular diseases. Human serum urate levels are largely determined by urate reabsorption and secretion in the kidney. Renal urate reabsorption is controlled via two proximal tubular urate transporters: apical URAT1 (SLC22A12) and basolateral URATv1/GLUT9 (SLC2A9). In contrast, the molecular mechanism(s) for renal urate secretion remain unknown. In this report, we demonstrate that an orphan transporter hNPT4 (human sodium phosphate transporter 4; SLC17A3) was a multispecific organic anion efflux transporter expressed in the kidneys and liver. hNPT4 was localized at the apical side of renal tubules and functioned as a voltage-driven urate transporter. Furthermore, loop diuretics, such as furosemide and bumetanide, substantially interacted with hNPT4. Thus, this protein is likely to act as a common secretion route for both drugs and may play an important role in diuretics-induced hyperuricemia. The in vivo role of hNPT4 was suggested by two hyperuricemia patients with missense mutations in SLC17A3. These mutated versions of hNPT4 exhibited reduced urate efflux when they were expressed in Xenopus oocytes. Our findings will complete a model of urate secretion in the renal tubular cell, where intracellular urate taken up via OAT1 and/or OAT3 from the blood exits from the cell into the lumen via hNPT4. PMID:20810651

Gingerol Fraction from Zingiber officinale Protects against Gentamicin-Induced Nephrotoxicity

PubMed Central

Rodrigues, Francisco A. P.; Prata, Mara M. G.; Oliveira, Iris C. M.; Alves, Natacha T. Q.; Freitas, Rosa E. M.; Monteiro, Helena S. A.; Silva, Jame's A.; Vieira, Paulo C.; Viana, Daniel A.; Libório, Alexandre B.

2014-01-01

Nephrotoxicity is the main complication of gentamicin (GM) treatment. GM induces renal damage by overproduction of reactive oxygen species and inflammation in proximal tubular cells. Phenolic compounds from ginger, called gingerols, have been demonstrated to have antioxidant and anti-inflammatory effects. We investigated if oral treatment with an enriched solution of gingerols (GF) would promote a nephroprotective effect in an animal nephropathy model. The following six groups of male Wistar rats were studied: (i) control group (CT group); (ii) gingerol solution control group (GF group); (iii) gentamicin treatment group (GM group), receiving 100 mg/kg of body weight intraperitoneally (i.p.); and (iv to vi) gentamicin groups also receiving GF, at doses of 6.25, 12.5, and 25 mg/kg, respectively (GM+GF groups). Animals from the GM group had a significant decrease in creatinine clearance and higher levels of urinary protein excretion. This was associated with markers of oxidative stress and nitric oxide production. Also, there were increases of the mRNA levels for proinflammatory cytokines (tumor necrosis factor alpha [TNF-α], interleukin-1β [IL-1β], IL-2, and gamma interferon [IFN-γ]). Histopathological findings of tubular degeneration and inflammatory cell infiltration reinforced GM-induced nephrotoxicity. All these alterations were attenuated by previous oral treatment with GF. Animals from the GM+GF groups showed amelioration in renal function parameters and reduced lipid peroxidation and nitrosative stress, in addition to an increment in the levels of glutathione (GSH) and superoxide dismutase (SOD) activity. Gingerols also promoted significant reductions in mRNA transcription for TNF-α, IL-2, and IFN-γ. These effects were dose dependent. These results demonstrate that GF promotes a nephroprotective effect on GM-mediated nephropathy by oxidative stress, inflammatory processes, and renal dysfunction. PMID:24395230

In-Situ TEM-STM Observations of SWCNT Ropes/Tubular Transformations

NASA Technical Reports Server (NTRS)

Sola, F.; Lebron-Colon, M.; Ferreira, P. J.; Fonseca, L. F.; Meador, M. A.; Marin, C.

2010-01-01

Single-walled carbon nanotubes (SWCNTs) prepared by the HiPco process were purified using a modified gas phase purification technique. A TEM-STM holder was used to study the morphological changes of SWCNT ropes as a function of applied voltage. Kink formation, buckling behavior, tubular transformation and eventual breakdown of the system were observed. The tubular formation was attributed to a transformation from SWCNT ropes to multi-walled carbon nanotube (MWCNT) structures. It is likely mediated by the patching and tearing mechanism which is promoted primarily by the mobile vacancies generated due to current-induced heating and, to some extent, by electron irradiation.

Cellular and subcellular localization of uncoupling protein 2 in the human kidney.

PubMed

Nigro, Michelangelo; De Sanctis, Claudia; Formisano, Pietro; Stanzione, Rosita; Forte, Maurizio; Capasso, Giovambattista; Gigliotti, Giuseppe; Rubattu, Speranza; Viggiano, Davide

2018-06-23

The uncoupling protein-2 (UCP2) is an anion transporter that plays a key role in the control of intracellular oxidative stress. In animal models UCP2 downregulation has several pathological sequelae, particularly affecting the vasculature and the kidney. Specifically, in these models kidney damage is highly favored in the absence of UCP2 in the context of experimental hypertension. Confirmations of these data in humans awaits further information, as no data are yet available concerning the cell-type and subcellular expression in the human kidney. In the present study, we aimed to characterize the UCP2 protein distribution in human kidney biopsies. In humans UCP2 is mainly localized in proximal convoluted tubule cells, with an intracytoplasmic punctate staining. UCP2 positive puncta are often localized at the interface between the endoplasmic reticulum and the mitochondria. Glomerular structures do not express UCP2 at detectable levels. The expression of UCP2 in proximal tubular cells may explain their relative propensity to damage in pathological conditions including the hypertensive disease.

Ionic requirements of proximal tubular sodium transport. I. Bicarbonate and chloride.

PubMed

Green, R; Giebisch, G

1975-11-01

Simultaneous perfusion of peritubular capillaries and proximal convoluted tubules was used to study the effect of varying transepithelial ionic gradients on ionic fluxes. Results show that net sodium influx and volume flux was one-third of normal when bicarbonate was absent, no chloride gradient existed, and glucose and amino acids were absent. Addition of bicarbonate to the luminal fluid did not restore the flux to normal, but peritubular bicarbonate did restore it. A chloride gradient imposed when no bicarbonate was present could only increase the fluxes slightly, but his flux was significant even after cyanide had poisoned transport. Reversing the chloride concentration gradient decreased the net sodium and volume fluxes whether bicarbonate was present or not. Glucose had no effect on fluxes, but substitution of Na by choline abolished them entirely. It is concluded that sodium is actively transported, that a chloride concentration gradient from lumen to plasma could account for up to 20% of net transport, and that peritubular bicarbonate is necessary for normal rates of sodium and fluid absorption.

Localization of a renal sodium-phosphate cotransporter gene to human chromosome 5q35

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kos, C.H.; Tenenhouse, H.S.; Tihy, F.

1994-01-01

Several Mendelian disorders of renal phosphate reabsorption, associated with hypophosphatemia and bone disease, have been described. These include X-linked hypophosphatemia (XLH), hereditary hypophosphatemic rickets with hypercalciuria, hypophosphatemic bone disease, and autosomal dominant and autosomal recessive hypophosphatemic rickets. The underlying mechanisms for renal phosphate wasting in these disorders remain unknown. The proximal tubule is the major site of renal phosphate reabsorption. Thus, mutations in genes that participate in the transepithelial transport of phosphate in this segment of the nephron may be responsible for these disorders. Recently, a cDNA encoding a renal proximal tubular, brush-border membrane Na[sup +]-phosphate cotransporter (NaP[sub i]-3) wasmore » cloned from human kidney cortex. As a first step in establishing whether mutations in the NaP[sub i]-3 gene are the cause of inherited disorders in phosphate homeostasis, the authors sought to determine its chromosomal localization. 9 refs., 1 fig.« less

Uranium XAFS analysis of kidney from rats exposed to uranium

PubMed Central

Kitahara, Keisuke; Numako, Chiya; Terada, Yasuko; Nitta, Kiyohumi; Homma-Takeda, Shino

2017-01-01

The kidney is the critical target of uranium exposure because uranium accumulates in the proximal tubules and causes tubular damage, but the chemical nature of uranium in kidney, such as its chemical status in the toxic target site, is poorly understood. Micro-X-ray absorption fine-structure (µXAFS) analysis was used to examine renal thin sections of rats exposed to uranyl acetate. The U L III-edge X-ray absorption near-edge structure spectra of bulk renal specimens obtained at various toxicological phases were similar to that of uranyl acetate: their edge position did not shift compared with that of uranyl acetate (17.175 keV) although the peak widths for some kidney specimens were slightly narrowed. µXAFS measurements of spots of concentrated uranium in the micro-regions of the proximal tubules showed that the edge jump slightly shifted to lower energy. The results suggest that most uranium accumulated in kidney was uranium (VI) but a portion might have been biotransformed in rats exposed to uranyl acetate. PMID:28244440

Uranium XAFS analysis of kidney from rats exposed to uranium.

PubMed

Kitahara, Keisuke; Numako, Chiya; Terada, Yasuko; Nitta, Kiyohumi; Shimada, Yoshiya; Homma-Takeda, Shino

2017-03-01

The kidney is the critical target of uranium exposure because uranium accumulates in the proximal tubules and causes tubular damage, but the chemical nature of uranium in kidney, such as its chemical status in the toxic target site, is poorly understood. Micro-X-ray absorption fine-structure (µXAFS) analysis was used to examine renal thin sections of rats exposed to uranyl acetate. The U L III -edge X-ray absorption near-edge structure spectra of bulk renal specimens obtained at various toxicological phases were similar to that of uranyl acetate: their edge position did not shift compared with that of uranyl acetate (17.175 keV) although the peak widths for some kidney specimens were slightly narrowed. µXAFS measurements of spots of concentrated uranium in the micro-regions of the proximal tubules showed that the edge jump slightly shifted to lower energy. The results suggest that most uranium accumulated in kidney was uranium (VI) but a portion might have been biotransformed in rats exposed to uranyl acetate.

[Effect of hyperthermal environment on urinary excretion of beta 2-microglobulin and hydrogen ion].

PubMed

Xu, G Z; Du, Y; Chen, D Z

1990-10-01

By randomized sampling, 1387 cases working in various circumstances in Chengdu Seamless Steel Tube Plant had their urine net acid clearance (NAC) and osmotic pressure (OSMP) measured, of whom 407 took urine beta 2m examination in addition. Results show that both NAC and OSMP are much higher in the hyperthermal group than in the non-hyperthermal group. There is no significant difference in beta 2m level between the two groups, which demonstrates that the function of proximal renal tubules of the workers in this plant has not been affected, as their working condition conforms to the standards for the prevention of workers made by the government. However, the beta 2m level in the male workers is obviously higher than that in the female. There exists the possibility that the males have contacted the toxic dust at a longer duration, which may be a factor involved in the tubular disorder. The rise of beta 2m together with age is regarded as due to senile decay. This study has provided available data for the set up of worker's prevention system.

Fanconi syndrome induced by tenofovir: A case report.

PubMed

Lify, Bouchra; Dabo, G; Nascimento, O; Iraqui, S; Elkhayat, S; Zamd, M; Medkouri, G; Benghanem, M; Ramdani, B; Sodqi, M M; Marih, L; Chakib, A; El FilaliMarhoum, K

2016-01-01

Tenofovir disoproxil fumarate (TDF) is a nucleotide reverse transcriptase inhibitor discovered in the USA in 2001. It is currently the treatment of choice for patients co-infected with human immunodeficiency virus (HIV) and hepatitis B virus. Its antiretroviral efficacy and good tolerance are responsible for the higher frequency of prescriptions compared with other nucleoside analogs. However, it can induce acute renal toxicity causing impairment of the proximal tubular function of the kidney. This is highly dependent on factors such as associated co-prescription didanosine or a protease inhibitor "boosted" with ritonavir, preexisting renal insufficiency, low body weight, or presence of associated diabetes. In contrast, long-term renal toxicity remains highly debated. Some studies describe a decrease in estimated glomerular filtration rate during prolonged treatment with TDF. Others reported renal safety even during prolonged use. The differences between patients enrolled in the different studies, the measured parameters and their interpretation could explain these discrepancies. We describe a case of a patient infected with HIV, who presented with Fanconi syndrome with acute renal failure six months after starting antiretroviral treatment including tenofovir.

Epithelial-to-Mesenchymal Transition in Diabetic Nephropathy: Fact or Fiction?

PubMed

Loeffler, Ivonne; Wolf, Gunter

2015-10-09

The pathophysiology of diabetic nephropathy (DN), one of the most serious complications in diabetic patients and the leading cause of end-stage renal disease worldwide, is complex and not fully elucidated. A typical hallmark of DN is the excessive deposition of extracellular matrix (ECM) proteins in the glomerulus and in the renal tubulointerstitium, eventually leading to glomerulosclerosis and interstitial fibrosis. Although it is obvious that myofibroblasts play a major role in the synthesis and secretion of ECM, the origin of myofibroblasts in DN remains the subject of controversial debates. A number of studies have focused on epithelial-to-mesenchymal transition (EMT) as one source of matrix-generating fibroblasts in the diseased kidney. EMT is characterized by the acquisition of mesenchymal properties by epithelial cells, preferentially proximal tubular cells and podocytes. In this review we comprehensively review the literature and discuss arguments both for and against a function of EMT in renal fibrosis in DN. While the precise extent of the contribution to nephrotic fibrosis is certainly arduous to quantify, the picture that emerges from this extensive body of literature suggests EMT as a major source of myofibroblasts in DN.

Pilot study of association of catechol-O-methyl transferase rs4680 genotypes with acute kidney injury and tubular stress after open heart surgery.

PubMed

Albert, Christian; Kube, Johanna; Haase-Fielitz, Anja; Dittrich, Annemarie; Schanze, Denny; Zenker, Martin; Kuppe, Hermann; Hetzer, Roland; Bellomo, Rinaldo; Mertens, Peter R; Haase, Michael

2014-01-01

To assess the association of genetic variants of catecholamine-O-methyltransferase (COMT) genotypes with acute kidney injury (AKI) and tubular stress after open heart surgery. We genotyped 195 patients for the COMT-Val158Met polymorphism and measured creatinine, neutrophil gelatinase-associated lipocalin and midkine. We analyzed the association between such polymorphisms and these kidney-related variables. Nonsignificantly more COMT LL patients developed RIFLE-AKI compared with non-LL patients (p = 0.11). Compared with HL and HH patients, LL patients who developed AKI had lower increases in serum creatinine. COMT LL patients had less pronounced release of tubular stress biomarkers (neutrophil gelatinase-associated lipocalin: p = 0.045, midkine: p = 0.072). COMT genotype may associate with different patterns of renal functional changes and tubular stress biomarker release response after open heart surgery.

Optical coherence tomography (OCT) of a murine model of chronic kidney disease

NASA Astrophysics Data System (ADS)

Wang, Hsing-Wen; Guo, Hengchang; Andrews, Peter M.; Anderson, Erik; Chen, Y.

2015-03-01

Chronic Kidney Disease (CKD) is characterized by a progressive loss in renal function over time. Pathology can provide valuable insights into the progression of CKD by analyzing the status of glomeruli and the uriniferous tubules over time. Optical coherence tomography (OCT) is a new procedure that can analyze the microscopic structure of the kidney in a non-invasive manner. This is especially important because there are significant artifacts associated with excision biopsies and immersion fixation procedures. Recently, we have shown that OCT can provide real time images of kidney microstructure and Doppler OCT (DOCT) can image glomerular renal blood flow in vivo without administrating exogenous contrast agents. In this study, we used OCT to evaluate CKD in a model induced by intravenous Adriamycin injection into Munich-Wistar rats. We evaluated tubular density and tubular diameter from OCT images at several post- Adriamycin induction time points and compared them with conventional light microscopic histological imaging. Proteinurea and serum creatinine were used as physiological markers of the extent of CKD. Preliminary OCT results revealed changes in tubular density due to tubular necrosis and interstitial fibrosis within the first 4 weeks following Adriamycin injection. From week 4 to 8 after Adriamycin induction, changes in tubular density and diameter occurred due to both tubular loss and tubular dilation. The results suggest OCT can provide additional information about kidney histopathology in CKD. DOCT revealed reduced blood flow in some glomeruli probably as a consequence of focal glomerularsclerosis.

Calcium-binding proteins annexin A2 and S100A6 are sensors of tubular injury and recovery in acute renal failure.

PubMed

Cheng, Chao-Wen; Rifai, Abdalla; Ka, Shuk-Man; Shui, Hao-Ai; Lin, Yuh-Feng; Lee, Wei-Hwa; Chen, Ann

2005-12-01

Rise in cellular calcium is associated with acute tubular necrosis, the most common cause of acute renal failure (ARF). The mechanisms that calcium signaling induce in the quiescent tubular cells to proliferate and differentiate during acute tubular necrosis have not been elucidated. Acute tubular necrosis induced in mice by single intravenous injection of uranyl nitrate and examined after 1, 3, 7, and 14 days. Renal function was monitored and kidneys were evaluated by histology, immunohistochemistry, Western blotting, in situ hybridization, and real-time reverse transcription-polymerase chain reaction (RT-PCR). Models of folic acid induced-ARF and ischemic/reperfusion (I/R) injury were similarly investigated. Analysis of mRNA expression of intracellular calcium and phospholipid-binding proteins demonstrated selective expression of S100A6 and Annexin A2 (Anxa2) in the renal cortex with marked elevation on day 3, and gradually decline on day 7 and further attenuation on day 14. Similarly, the expression of both proteins, as demonstrated by immunohistochemistry and Western blot analysis, was increased and reached the peak level on day 7 and then gradually declined by day 14. Vimentin, a marker of dedifferentiated cells, was highly expressed during the recovery phase. Combined in situ hybridization immunohistochemistry revealed colocalization of both S100A6 and Anxa2 with proliferating cell nuclear antigen (PCNA). The universality of this phenomenon was confirmed in two other mouse acute tubular necrosis models, the ischemic-reperfusion injury and folic acid-induced ARF. Collectively, these findings demonstrate that S100A6 and Anxa2 expression, initiated in response to tubular injury, persist in parallel throughout the recovery process of tubular cells in acute renal failure.

Evaluation of cell viability and functionality in vessel-like bioprintable cell-laden tubular channels.

PubMed

Yu, Yin; Zhang, Yahui; Martin, James A; Ozbolat, Ibrahim T

2013-09-01

Organ printing is a novel concept recently introduced in developing artificial three-dimensional organs to bridge the gap between transplantation needs and organ shortage. One of the major challenges is inclusion of blood-vessellike channels between layers to support cell viability, postprinting functionality in terms of nutrient transport, and waste removal. In this research, we developed a novel and effective method to print tubular channels encapsulating cells in alginate to mimic the natural vascular system. An experimental investigation into the influence on cartilage progenitor cell (CPCs) survival, and the function of printing parameters during and after the printing process were presented. CPC functionality was evaluated by checking tissue-specific genetic marker expression and extracellular matrix production. Our results demonstrated the capability of direct fabrication of cell-laden tubular channels by our newly designed coaxial nozzle assembly and revealed that the bioprinting process could induce quantifiable cell death due to changes in dispensing pressure, coaxial nozzle geometry, and biomaterial concentration. Cells were able to recover during incubation, as well as to undergo differentiation with high-level cartilage-associated gene expression. These findings may not only help optimize our system but also can be applied to biomanufacturing of 3D functional cellular tissue engineering constructs for various organ systems.

Long-term functional outcomes after penoscrotal hypospadias repair: A retrospective comparative study of proximal TIP, Onlay, and Duckett.

PubMed

Hueber, Pierre-Alain; Salgado Diaz, Monica; Chaussy, Yann; Franc-Guimond, Julie; Barrieras, Diego; Houle, Anne-Marie

2016-08-01

A variety of techniques are available for proximal hypospadias repair. Onlay, proximal tubularized incised plate (TIP), and Duckett are among the popular choices because they can be performed as a one-step procedure. However, the decision to select a procedure often comes down to the surgeon's preference rather than that supported by evidence-based data. In particular, there is a paucity of literature on the long-term urinary outcomes after proximal hypospadias repair. The aim of this study was to evaluate the evolution of long-term uroflowmetry parameters after proximal hypospadias surgery over a long-term follow-up including the adolescent period. Files from patients who underwent primary proximal hypospadias repair at our institution between 1997 and 2001 were reviewed. Only patients with documented serial postoperative uroflowmetry profiles at follow-up visits were included. Comparison between surgeries (pTIP vs. Onlay vs. Duckett) was performed according to the following postoperative time interval endpoints: 0-1 years, 1-2, >2-4, >4-6, >6-10, >10-12, and >12 years. Maximal urinary flow rate (Qmax) in relation to voiding volume (VV) adjusted for age or body surface area (BSA) were also evaluated in comparison to normal children using established Miskolc nomograms and compared between surgery techniques. Fifty-two patients met the inclusion criteria with a median follow-up of 10 years: 25 (59.6%) TIP, 18 (34/6%) Onlay, and nine (17.3%) Duckett. Overall, Qmax increased progressively according to time and age in particular during the period covering adolescence. At follow-up 12 years postoperatively, median Qmax values were 18.5 mL/second, 13.8 mL/second and 16.6 mL/second for TIP, Onlay, and Duckett, respectively, with no significant differenced detected between groups (p = 0.5) see figure). Compared with normal children when adjusted for voiding volume and BSA, the proportion of obstructive uroflowmetry patterns defined as Qmax<25th percentile of nomograms was more prevalent in patients aged 3-7 years old at 83.8% but decreased to less than 21.2% in patients aged >13 years for all procedures (see figure). These results are consistent with previous work showing frequently reduced Qmax after hypospadias surgery with great potential for improvement at puberty. These results suggest that the obstructive urinary flow pattern observed in patients early on is a frequent finding after proximal hypospadias surgery. However, because of the remarkable improvement observed at puberty a watchful waiting approach is proposed in order to avoid unnecessary intervention. Copyright © 2016 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.

The anatomy and physiology of the suspensory apparatus of the distal phalanx.

PubMed

Pollitt, Christopher C

2010-04-01

The equine hoof capsule protects the softer, more sensitive, structures within. Failure of the connection between hoof and bone (suspensory apparatus of the distal phalanx or SADP) results in the crippling lameness of laminitis. Active basal cell proliferation occurs principally in tubular hoof and proximal and distal lamellae. The remaining lamellae are virtually non-proliferative and the hoof wall moves past the stationary distal phalanx, by controlled activation and inhibition of constituent proteases. The lamellar corium derives most of its blood supply from the branches of the terminal arch which perforate the distal phalanx. Valveless veins within the foot can be exploited clinically for retrograde venous therapy or contrast radiography (venography). The basement membrane (BM) forms the interface between the lamellar epidermis and the adjacent dermis and the plasma membrane of each lamellar basal cell is attached to the BM by numerous electron dense adhesion plaques or hemidesmosomes the ultimate attachment unit of the SADP. Laminitis destroys and dislocates the BM and its components and without an intact, functional BM, the structure and function of the lamellar epidermis is pathologically compromised. Transcription and activation of constituent proteases occurs in normal hoof lamellae but in increased amounts during laminitis. Copyright 2010 Elsevier Inc. All rights reserved.

Rolled-up Functionalized Nanomembranes as Three-Dimensional Cavities for Single Cell Studies

PubMed Central

2014-01-01

We use micropatterning and strain engineering to encapsulate single living mammalian cells into transparent tubular architectures consisting of three-dimensional (3D) rolled-up nanomembranes. By using optical microscopy, we demonstrate that these structures are suitable for the scrutiny of cellular dynamics within confined 3D-microenvironments. We show that spatial confinement of mitotic mammalian cells inside tubular architectures can perturb metaphase plate formation, delay mitotic progression, and cause chromosomal instability in both a transformed and nontransformed human cell line. These findings could provide important clues into how spatial constraints dictate cellular behavior and function. PMID:24598026

Tube support for moisture separator reheater

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabatino, R.A.

1987-08-11

In combination with a moisture separator reheater for a nuclear steam generating power plant, a reheater is described comprising: a sealed elongated substantially horizontal tubular shell member, a cycle fluid inlet passing through the shell member in predetermined position, mositure separator means positioned within the shell member proximate the bottom portion thereof, heat exchanger means comprising a plurality of elongated metallic U-shaped members disposed substantially within the shell member, a tube sheet member supporing the U-shaped tube members at one end thereof. The improvement consists of: the tube support member means proximate the U-bend portion of the U-shaped tube membersmore » each comprising an upper movable tube support member and a lower immovable tube support member, the remainder of the tube support means being immovable, the upper movable tube support member spacing and supporting the top leg portions of the U-shaped tube members, the lower immovable tube support member spacing and supporting the bottom leg portions of the U-shaped tube members, whereby the top leg portions of the U-shaped tube members proximate the U-bend are permitted to move to compensate for any increase in radius in the U-bend portion of the U-shaped tube member due to thermal expansion.« less

MitoQ blunts mitochondrial and renal damage during cold preservation of porcine kidneys.

PubMed

Parajuli, Nirmala; Campbell, Lia H; Marine, Akira; Brockbank, Kelvin G M; Macmillan-Crow, Lee Ann

2012-01-01

Cold preservation has greatly facilitated the use of cadaveric kidneys for transplantation but damage occurs during the preservation episode. It is well established that oxidant production increases during cold renal preservation and mitochondria are a key target for injury. Our laboratory has demonstrated that cold storage of renal cells and rat kidneys leads to increased mitochondrial superoxide levels and mitochondrial electron transport chain damage, and that addition of Mitoquinone (MitoQ) to the preservation solutions blunted this injury. In order to better translate animal studies, the inclusion of large animal models is necessary to develop safe preclinical protocols. Therefore, we tested the hypothesis that addition of MitoQ to cold storage solution preserves mitochondrial function by decreasing oxidative stress, leading to less renal tubular damage during cold preservation of porcine kidneys employing a standard criteria donor model. Results showed that cold storage significantly induced oxidative stress (nitrotyrosine), renal tubular damage, and cell death. Using High Resolution Respirometry and fresh porcine kidney biopsies to assess mitochondrial function we showed that MitoQ significantly improved complex II/III respiration of the electron transport chain following 24 hours of cold storage. In addition, MitoQ blunted oxidative stress, renal tubular damage, and cell death after 48 hours. These results suggested that MitoQ decreased oxidative stress, tubular damage and cell death by improving mitochondrial function during cold storage. Therefore this compound should be considered as an integral part of organ preservation solution prior to transplantation.

MitoQ Blunts Mitochondrial and Renal Damage during Cold Preservation of Porcine Kidneys

PubMed Central

Parajuli, Nirmala; Campbell, Lia H.; Marine, Akira; Brockbank, Kelvin G. M.; MacMillan-Crow, Lee Ann

2012-01-01

Cold preservation has greatly facilitated the use of cadaveric kidneys for transplantation but damage occurs during the preservation episode. It is well established that oxidant production increases during cold renal preservation and mitochondria are a key target for injury. Our laboratory has demonstrated that cold storage of renal cells and rat kidneys leads to increased mitochondrial superoxide levels and mitochondrial electron transport chain damage, and that addition of Mitoquinone (MitoQ) to the preservation solutions blunted this injury. In order to better translate animal studies, the inclusion of large animal models is necessary to develop safe preclinical protocols. Therefore, we tested the hypothesis that addition of MitoQ to cold storage solution preserves mitochondrial function by decreasing oxidative stress, leading to less renal tubular damage during cold preservation of porcine kidneys employing a standard criteria donor model. Results showed that cold storage significantly induced oxidative stress (nitrotyrosine), renal tubular damage, and cell death. Using High Resolution Respirometry and fresh porcine kidney biopsies to assess mitochondrial function we showed that MitoQ significantly improved complex II/III respiration of the electron transport chain following 24 hours of cold storage. In addition, MitoQ blunted oxidative stress, renal tubular damage, and cell death after 48 hours. These results suggested that MitoQ decreased oxidative stress, tubular damage and cell death by improving mitochondrial function during cold storage. Therefore this compound should be considered as an integral part of organ preservation solution prior to transplantation. PMID:23139796

Tissue-engineered trachea regeneration using decellularized trachea matrix treated with laser micropore technique.

PubMed

Xu, Yong; Li, Dan; Yin, Zongqi; He, Aijuan; Lin, Miaomiao; Jiang, Gening; Song, Xiao; Hu, Xuefei; Liu, Yi; Wang, Jinpeng; Wang, Xiaoyun; Duan, Liang; Zhou, Guangdong

2017-08-01

Tissue-engineered trachea provides a promising approach for reconstruction of long segmental tracheal defects. However, a lack of ideal biodegradable scaffolds greatly restricts its clinical translation. Decellularized trachea matrix (DTM) is considered a proper scaffold for trachea cartilage regeneration owing to natural tubular structure, cartilage matrix components, and biodegradability. However, cell residual and low porosity of DTM easily result in immunogenicity and incomplete cartilage regeneration. To address these problems, a laser micropore technique (LMT) was applied in the current study to modify trachea sample porosity to facilitate decellular treatment and cell ingrowth. Decellularization processing demonstrated that cells in LMT treated samples were more easily removed compared with untreated native trachea. Furthermore, after optimizing the protocols of LMT and decellular treatments, the LMT-treated DTM (LDTM) could retain their original tubular shape with only mild extracellular matrix damage. After seeding with chondrocytes and culture in vitro for 8 weeks, the cell-LDTM constructs formed tubular cartilage with relatively homogenous cell distribution in both micropores and bilateral surfaces. In vivo results further confirmed that the constructs could form mature tubular cartilage with increased DNA and cartilage matrix contents, as well as enhanced mechanical strength, compared with native trachea. Collectively, these results indicate that LDTM is an ideal scaffold for tubular cartilage regeneration and, thus, provides a promising strategy for functional reconstruction of trachea cartilage. Lacking ideal biodegradable scaffolds greatly restricts development of tissue-engineered trachea. Decellularized trachea matrix (DTM) is considered a proper scaffold for trachea cartilage regeneration. However, cell residual and low porosity of DTM easily result in immunogenicity and incomplete cartilage regeneration. By laser micropore technique (LMT), the current study efficiently enhanced the porosity and decellularized efficacy of DTM. The LMT-treated DTM basically retained the original tubular shape with mild matrix damage. After chondrocyte seeding followed by in vitro culture and in vivo implantation, the constructs formed mature tubular cartilage with matrix content and mechanical strength similar to native trachea. The current study provides an ideal scaffold and a promising strategy for cartilage regeneration and functional reconstruction of trachea. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Compensatory regulation of Na+ absorption by Na+/H+ exchanger and Na+-Cl- cotransporter in zebrafish (Danio rerio)

PubMed Central

2013-01-01

Introduction In mammals, internal Na+ homeostasis is maintained through Na+ reabsorption via a variety of Na+ transport proteins with mutually compensating functions, which are expressed in different segments of the nephrons. In zebrafish, Na+ homeostasis is achieved mainly through the skin/gill ionocytes, namely Na+/H+ exchanger (NHE3b)-expressing H+-ATPase rich (HR) cells and Na+-Cl- cotransporter (NCC)-expressing NCC cells, which are functionally homologous to mammalian proximal and distal convoluted tubular cells, respectively. The present study aimed to investigate whether or not the functions of HR and NCC ionocytes are differentially regulated to compensate for disruptions of internal Na+ homeostasis and if the cell differentiation of the ionocytes is involved in this regulation pathway. Results Translational knockdown of ncc caused an increase in HR cell number and a resulting augmentation of Na+ uptake in zebrafish larvae, while NHE3b loss-of-function caused an increase in NCC cell number with a concomitant recovery of Na+ absorption. Environmental acid stress suppressed nhe3b expression in HR cells and decreased Na+ content, which was followed by up-regulation of NCC cells accompanied by recovery of Na+ content. Moreover, knockdown of ncc resulted in a significant decrease of Na+ content in acid-acclimated zebrafish. Conclusions These results provide evidence that HR and NCC cells exhibit functional redundancy in Na+ absorption, similar to the regulatory mechanisms in mammalian kidney, and suggest this functional redundancy is a critical strategy used by zebrafish to survive in a harsh environment that disturbs body fluid Na+ homeostasis. PMID:23924428

Cystinosis Presenting with Findings of Bartter Syndrome

PubMed Central

Özkan, Behzat; Çayır, Atilla; Koşan, Celalettin; Alp, Handan

2011-01-01

A five-year-old boy was referred to our pediatric clinic for evaluation of failure to thrive, headache, intermittent high fever, restlessness, polyuria, and polydipsia. His weight and height measurements were under the 3rd percentile. Clinical findings consisted of frontal bossing, carious teeth, O-bain deformity of the lower extremities, and moderate dehydration. The presence of metabolic alkalosis, hypokalemia, hypochloremia, and high renin and aldosterone levels were suggestive of Bartter syndrome and a treatment regimen for Bartter syndrome was started. At follow-up, the polyuria and hyponatremia were found to persist. A reassessment of the patient revealed findings consistent with proximal renal tubular acidosis such as metabolic acidosis with a high urinary pH, proteinuria, aminoaciduria with phosphaturia and hypercalciuria. Based on the presence of parental consanguinity as well as polyuria, proteinuria, low tubular reabsorption of phosphorus, generalized aminoaciduria, light yellow skin and hair color, the probable diagnosis of cystinosis was established and was confirmed by slit-lamp examination of the cornea showing cystine crystal deposition. Our case is a good example demonstrating that development of metabolic alkalosis does not exclude cystinosis and that all findings of the patient should be thoroughly evaluated. Conflict of interest:None declared. PMID:21750641

Cystinosis presenting with findings of Bartter syndrome.

PubMed

Özkan, Behzat; Çayır, Atilla; Koşan, Celalettin; Alp, Handan

2011-01-01

A five-year-old boy was referred to our pediatric clinic for evaluation of failure to thrive, headache, intermittent high fever, restlessness, polyuria, and polydipsia. His weight and height measurements were under the 3rd percentile. Clinical findings consisted of frontal bossing, carious teeth, O-bain deformity of the lower extremities, and moderate dehydration. The presence of metabolic alkalosis, hypokalemia, hypochloremia, and high renin and aldosterone levels were suggestive of Bartter syndrome and a treatment regimen for Bartter syndrome was started. At follow-up, the polyuria and hyponatremia were found to persist. A reassessment of the patient revealed findings consistent with proximal renal tubular acidosis such as metabolic acidosis with a high urinary pH, proteinuria, aminoaciduria with phosphaturia and hypercalciuria. Based on the presence of parental consanguinity as well as polyuria, proteinuria, low tubular reabsorption of phosphorus, generalized aminoaciduria, light yellow skin and hair color, the probable diagnosis of cystinosis was established and was confirmed by slit-lamp examination of the cornea showing cystine crystal deposition. Our case is a good example demonstrating that development of metabolic alkalosis does not exclude cystinosis and that all findings of the patient should be thoroughly evaluated. ©Journal of Clinical Research in Pediatric Endocrinology, Published by Galenos Publishing.

Insulative laser shell coupler

DOEpatents

Arnold, Phillip A.; Anderson, Andrew T.; Alger, Terry W.

1994-01-01

A segmented coaxial laser shell assembly having at least two water jacket sections, two pairs of interconnection half rings, a dialectric break ring, and a pair of threaded ring sections. Each water jacket section with an inner tubular section that defines an inner laser cavity with water paths adjacent to at least a portion of the exterior of the inner tubular section, and mating faces at the end of the water jacket section through which the inner laser cavity opens and which defines at least one water port therethrough in communication with the water jackets. The water paths also define in their external surface a circumferential notch set back from and in close proximity to the mating face. The dielectric break ring has selected thickness and is placed between, and in coaxial alignment with, the mating faces of two of the adjacent water jacket sections. The break ring also defines an inner laser cavity of the same size and shape as the inner laser cavity of the water jacket sections and at least one water passage through the break ring to communicate with at least one water port through the mating faces of the water jacket sections.

Insulative laser shell coupler

DOEpatents

Arnold, P.A.; Anderson, A.T.; Alger, T.W.

1994-09-20

A segmented coaxial laser shell assembly having at least two water jacket sections, two pairs of interconnection half rings, a dielectric break ring, and a pair of threaded ring sections is disclosed. Each water jacket section with an inner tubular section that defines an inner laser cavity with water paths adjacent to at least a portion of the exterior of the inner tubular section, and mating faces at the end of the water jacket section through which the inner laser cavity opens and which defines at least one water port therethrough in communication with the water jackets. The water paths also define in their external surface a circumferential notch set back from and in close proximity to the mating face. The dielectric break ring has selected thickness and is placed between, and in coaxial alignment with, the mating faces of two of the adjacent water jacket sections. The break ring also defines an inner laser cavity of the same size and shape as the inner laser cavity of the water jacket sections and at least one water passage through the break ring to communicate with at least one water port through the mating faces of the water jacket sections. 4 figs.

A new algorithm for primary hypospadias repair based on tip urethroplasty.

PubMed

Sozubir, Selami; Snodgrass, Warren

2003-08-01

Decision making in hypospadias repair potentially can be simplified by tubularized incised plate (TIP) urethroplasty. The authors report management and outcomes in a consecutive series of primary hypospadias repairs in which the intent was to perform TIP. Records of 106 consecutive boys undergoing hypospadias repair by 1 surgeon were reviewed. Position of the meatus, degree and management of curvature, technical details of the urethroplasty, and postoperative complications were recorded. Curvature was noted in 24 (23%) of patients, but could be corrected with preservation of the urethral plate in all but 3. In another boy, the incised plate was thought "unhealthy" for tubularization. The remaining 102 underwent TIP, of whom, 75 had distal and 27 had proximal hypospadias. Complications, primarily fistulas, occurred in 14 (13%) of these patients. The other 4 boys underwent staged repairs that utilized TIP for the glanular urethra at the second operation. The authors found decision making was no longer determined by meatal location as in the past, but by severity of curvature and appearance of the incised urethral plate. Because severe curvature requiring plate transection or an "unhealthy" incised plate are uncommonly encountered, TIP repair can be performed for most hypospadias operations.

Thalidomide Ameliorates Inflammation and Vascular Injury but Aggravates Tubular Damage in the Irradiated Mouse Kidney

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scharpfenecker, Marion, E-mail: m.scharpfenecker@nki.nl; Floot, Ben; Russell, Nicola S.

Purpose: The late side effects of kidney irradiation include vascular damage and fibrosis, which are promoted by an irradiation-induced inflammatory response. We therefore treated kidney-irradiated mice with the anti-inflammatory and angiogenesis-modulating drug thalidomide in an attempt to prevent the development of late normal tissue damage and radiation nephropathy in the mouse kidney. Methods and Materials: Kidneys of C57Bl/6 mice were irradiated with a single dose of 14 Gy. Starting from week 16 after irradiation, the mice were fed with thalidomide-containing chow (100 mg/kg body weight/day). Gene expression and kidney histology were analyzed at 40 weeks and blood samples at 10, 20, 30, andmore » 40 weeks after irradiation. Results: Thalidomide improved the vascular structure and vessel perfusion after irradiation, associated with a normalization of pericyte coverage. The drug also reduced infiltration of inflammatory cells but could not suppress the development of fibrosis. Irradiation-induced changes in hematocrit and blood urea nitrogen levels were not rescued by thalidomide. Moreover, thalidomide worsened tubular damage after irradiation and also negatively affected basal tubular function. Conclusions: Thalidomide improved the inflammatory and vascular side effects of kidney irradiation but could not reverse tubular toxicity, which probably prevented preservation of kidney function.« less

Bidirectional signalling between EphA2 and ephrinA1 increases tubular cell attachment, laminin secretion and modulates erythropoietin expression after renal hypoxic injury.

PubMed

Rodriguez, Stéphane; Rudloff, Stefan; Koenig, Katrin Franziska; Karthik, Swapna; Hoogewijs, David; Huynh-Do, Uyen

2016-08-01

Acute kidney injury (AKI) is common in hospitalized patients and has a poor prognosis, the severity of AKI being linked to progression to chronic kidney disease. This stresses the need to search for protective mechanisms during the acute phase. We investigated kidney repair after hypoxic injury using a rat model of renal artery branch ligation, which led to an oxygen gradient vertical to the corticomedullary axis. Three distinct zones were observed: tubular necrosis, infarction border zone and preserved normal tissue. EphA2 is a receptor tyrosine kinase with pivotal roles in cell architecture, migration and survival, upon juxtacrine contact with its membrane-bound ligand EphrinA1. Following hypoxia, EphA2 was up-regulated in cortical and medullary tubular cells, while EphrinA1 was up-regulated in interstitial cells adjacent to peritubular capillaries. Moreover, erythropoietin (EPO) messenger RNA (mRNA) was strongly expressed in the border zone of infarcted kidney within the first 6 h. To gain more insight into the biological impact of EphA2 and EphrinA1 up-regulation, we activated the signalling pathways in vitro using recombinant EphrinA1/Fc or EphA2/Fc proteins. Stimulation of EphA2 forward signalling in the proximal tubular cell line HK2 increased cell attachment and laminin secretion at the baso-lateral side. Conversely, activation of reverse signalling through EphrinA1 expressed by Hep3B cells promoted EPO production at both the transcriptional and protein level. Strikingly, in co-culture experiments, juxtacrine contact between EphA2 expressing MDCK and EphrinA1 expressing Hep3B was sufficient to induce a significant up-regulation of EPO mRNA production in the latter cells, even in the absence of hypoxic conditions. The synergistic effects of EphA2 and hypoxia led to a 15-20-fold increase of EPO expression. Collectively, our results suggest an important role of EphA2/EphrinA1 signalling in kidney repair after hypoxic injury through stimulation of (i) tubular cell attachment, (ii) secretion of basal membrane proteins and (iii) EPO production. These findings could thus pave the way to new therapeutic approaches.

Cellular localization of uranium in the renal proximal tubules during acute renal uranium toxicity.

PubMed

Homma-Takeda, Shino; Kitahara, Keisuke; Suzuki, Kyoko; Blyth, Benjamin J; Suya, Noriyoshi; Konishi, Teruaki; Terada, Yasuko; Shimada, Yoshiya

2015-12-01

Renal toxicity is a hallmark of uranium exposure, with uranium accumulating specifically in the S3 segment of the proximal tubules causing tubular damage. As the distribution, concentration and dynamics of accumulated uranium at the cellular level is not well understood, here, we report on high-resolution quantitative in situ measurements by high-energy synchrotron radiation X-ray fluorescence analysis in renal sections from a rat model of uranium-induced acute renal toxicity. One day after subcutaneous administration of uranium acetate to male Wistar rats at a dose of 0.5 mg uranium kg(-1) body weight, uranium concentration in the S3 segment of the proximal tubules was 64.9 ± 18.2 µg g(-1) , sevenfold higher than the mean renal uranium concentration (9.7 ± 2.4 µg g(-1) ). Uranium distributed into the epithelium of the S3 segment of the proximal tubules and highly concentrated uranium (50-fold above mean renal concentration) in micro-regions was found near the nuclei. These uranium levels were maintained up to 8 days post-administration, despite more rapid reductions in mean renal concentration. Two weeks after uranium administration, damaged areas were filled with regenerating tubules and morphological signs of tissue recovery, but areas of high uranium concentration (100-fold above mean renal concentration) were still found in the epithelium of regenerating tubules. These data indicate that site-specific accumulation of uranium in micro-regions of the S3 segment of the proximal tubules and retention of uranium in concentrated areas during recovery are characteristics of uranium behavior in the kidney. Copyright © 2015 John Wiley & Sons, Ltd.

Differential patterns of injury to the proximal tubule of renal cortical slices following in vitro exposure to mercuric chloride, potassium dichromate, or hypoxic conditions.

PubMed

Ruegg, C E; Gandolfi, A J; Nagle, R B; Brendel, K

1987-09-15

The innate susceptibility of renal cell types to these agents was investigated using precision-cut rabbit renal cortical slices made perpendicular to the cortical-papillary axis. Slices were incubated in DME/F12 medium containing 10 microM, 100 microM, or 1 mM concentrations of either metal for 12 hr or in Krebs-Hepes buffer gassed with nitrogen (100%) for 0.75 to 5 hr of hypoxic exposure. To simulate postischemic reperfusion, some slices were transferred to vessels gassed with oxygen after an initial hypoxic period. Mercuric chloride (100 microM) exposure resulted in damage to the straight regions of proximal tubules by 12 hr leaving convoluted regions unaffected. Hypoxia (2.25 hr) and potassium dichromate (100 microM for 12 hr) both caused injury to the convoluted proximal tubules without affecting straight proximal tubular regions. Mercury concentrations of 10 microM and 1 mM had no effect or injured all cell types within the slice, respectively. Similar results were observed for hypoxic periods less than 1.5 hr or greater than 3 hr of exposure. Potassium dichromate had no measurable affect at 10 microM, but at 1 mM focal lesions were observed after 4 hr of exposure, and by 12 hr all cell types within the slice were affected. Intracellular potassium content normalized to DNA correlated well, but always preceded the pathological lesions observed. These results demonstrate that injury to specific regions of the proximal tubule by these agents relates to an innate susceptibility of the intoxicated cell type independent of physiologic feedback or blood delivery patterns proposed as mechanisms of selective injury from in vivo studies.

Interferon-γ Reduces the Proliferation of Primed Human Renal Tubular Cells.

PubMed

García-Sánchez, Omar; López-Novoa, José Miguel; López-Hernández, Francisco J

2014-01-01

Chronic kidney disease (CKD) is a progressive deterioration of the kidney function, which may eventually lead to renal failure and the need for dialysis or kidney transplant. Whether initiated in the glomeruli or the tubuli, CKD is characterized by progressive nephron loss, for which the process of tubular deletion is of key importance. Tubular deletion results from tubular epithelial cell death and defective repair, leading to scarring of the renal parenchyma. Several cytokines and signaling pathways, including transforming growth factor-β (TGF-β) and the Fas pathway, have been shown to participate in vivo in tubular cell death. However, there is some controversy about their mode of action, since a direct effect on normal tubular cells has not been demonstrated. We hypothesized that epithelial cells would require specific priming to become sensitive to TGF-β or Fas stimulation and that this priming would be brought about by specific mediators found in the pathological scenario. Herein we studied whether the combined effect of several stimuli known to take part in CKD progression, namely TGF-β, tumor necrosis factor-α, interferon-γ (IFN-γ), and Fas stimulation, on primed resistant human tubular cells caused cell death or reduced proliferation. We demonstrate that these cytokines have no synergistic effect on the proliferation or viability of human kidney (HK2) cells. We also demonstrate that IFN-γ, but not the other stimuli, reduces the proliferation of cycloheximide-primed HK2 cells without affecting their viability. Our results point at a potentially important role of IFN-γ in defective repair, leading to nephron loss during CKD.

Interferon-γ Reduces the Proliferation of Primed Human Renal Tubular Cells

PubMed Central

García-Sánchez, Omar; López-Novoa, José Miguel; López-Hernández, Francisco J.

2014-01-01

Background/Aims Chronic kidney disease (CKD) is a progressive deterioration of the kidney function, which may eventually lead to renal failure and the need for dialysis or kidney transplant. Whether initiated in the glomeruli or the tubuli, CKD is characterized by progressive nephron loss, for which the process of tubular deletion is of key importance. Tubular deletion results from tubular epithelial cell death and defective repair, leading to scarring of the renal parenchyma. Several cytokines and signaling pathways, including transforming growth factor-β (TGF-β) and the Fas pathway, have been shown to participate in vivo in tubular cell death. However, there is some controversy about their mode of action, since a direct effect on normal tubular cells has not been demonstrated. We hypothesized that epithelial cells would require specific priming to become sensitive to TGF-β or Fas stimulation and that this priming would be brought about by specific mediators found in the pathological scenario. Methods Herein we studied whether the combined effect of several stimuli known to take part in CKD progression, namely TGF-β, tumor necrosis factor-α, interferon-γ (IFN-γ), and Fas stimulation, on primed resistant human tubular cells caused cell death or reduced proliferation. Results We demonstrate that these cytokines have no synergistic effect on the proliferation or viability of human kidney (HK2) cells. We also demonstrate that IFN-γ, but not the other stimuli, reduces the proliferation of cycloheximide-primed HK2 cells without affecting their viability. Conclusion Our results point at a potentially important role of IFN-γ in defective repair, leading to nephron loss during CKD. PMID:24575118

Tubular collagen scaffolds with radial elasticity for hollow organ regeneration.

PubMed

Versteegden, Luuk R; van Kampen, Kenny A; Janke, Heinz P; Tiemessen, Dorien M; Hoogenkamp, Henk R; Hafmans, Theo G; Roozen, Edwin A; Lomme, Roger M; van Goor, Harry; Oosterwijk, Egbert; Feitz, Wout F; van Kuppevelt, Toin H; Daamen, Willeke F

2017-04-01

Tubular collagen scaffolds have been used for the repair of damaged hollow organs in regenerative medicine, but they generally lack the ability to reversibly expand in radial direction, a physiological characteristic seen in many native tubular organs. In this study, tubular collagen scaffolds were prepared that display a shape recovery effect and therefore exhibit radial elasticity. Scaffolds were constructed by compression of fibrillar collagen around a star-shaped mandrel, mimicking folds in a lumen, a typical characteristic of empty tubular hollow organs, such as ureter or urethra. Shape recovery effect was introduced by in situ fixation using a star-shaped mandrel, 3D-printed clamps and cytocompatible carbodiimide crosslinking. Prepared scaffolds expanded upon increase of luminal pressure and closed to the star-shaped conformation after removal of pressure. In this study, we applied this method to construct a scaffold mimicking the dynamics of human urethra. Radial expansion and closure of the scaffold could be iteratively performed for at least 1000 cycles, burst pressure being 132±22mmHg. Scaffolds were seeded with human epithelial cells and cultured in a bioreactor under dynamic conditions mimicking urination (pulse flow of 21s every 2h). Cells adhered and formed a closed luminal layer that resisted flow conditions. In conclusion, a new type of a tubular collagen scaffold has been constructed with radial elastic-like characteristics based on the shape of the scaffold, and enabling the scaffold to reversibly expand upon increase in luminal pressure. These scaffolds may be useful for regenerative medicine of tubular organs. In this paper, a new type I collagen-based tubular scaffold is presented that possesses intrinsic radial elasticity. This characteristic is key to the functioning of a number of tubular organs including blood vessels and organs of the gastrointestinal and urogenital tract. The scaffold was given a star-shaped lumen by physical compression and chemical crosslinking, mimicking the folding pattern observed in many tubular organs. In rest, the lumen is closed but it opens upon increase of luminal pressure, e.g. when fluids pass. Human epithelial cells seeded on the luminal side adhered well and were compatible with voiding dynamics in a bioreactor. Collagen scaffolds with radial elasticity may be useful in the regeneration of dynamic tubular organs. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Nonlinear Analysis of Bonded Composite Tubular Lap Joints

NASA Technical Reports Server (NTRS)

Oterkus, E.; Madenci, E.; Smeltzer, S. S., III; Ambur, D. R.

2005-01-01

The present study describes a semi-analytical solution method for predicting the geometrically nonlinear response of a bonded composite tubular single-lap joint subjected to general loading conditions. The transverse shear and normal stresses in the adhesive as well as membrane stress resultants and bending moments in the adherends are determined using this method. The method utilizes the principle of virtual work in conjunction with nonlinear thin-shell theory to model the adherends and a cylindrical shear lag model to represent the kinematics of the thin adhesive layer between the adherends. The kinematic boundary conditions are imposed by employing the Lagrange multiplier method. In the solution procedure, the displacement components for the tubular joint are approximated in terms of non-periodic and periodic B-Spline functions in the longitudinal and circumferential directions, respectively. The approach presented herein represents a rapid-solution alternative to the finite element method. The solution method was validated by comparison against a previously considered tubular single-lap joint. The steep variation of both peeling and shearing stresses near the adhesive edges was successfully captured. The applicability of the present method was also demonstrated by considering tubular bonded lap-joints subjected to pure bending and torsion.

The use of fibrous, supramolecular membranes and human tubular cells for renal epithelial tissue engineering: towards a suitable membrane for a bioartificial kidney.

PubMed

Dankers, Patricia Y W; Boomker, Jasper M; Huizinga-van der Vlag, Ali; Smedts, Frank M M; Harmsen, Martin C; van Luyn, Marja J A

2010-11-10

A bioartificial kidney, which is composed of a membrane cartridge with renal epithelial cells, can substitute important kidney functions in patients with renal failure. A particular challenge is the maintenance of monolayer integrity and specialized renal epithelial cell functions ex vivo. We hypothesized that this can be improved by electro-spun, supramolecular polymer membranes which show clear benefits in ease of processability. We found that after 7 d, in comparison to conventional microporous membranes, renal tubular cells cultured on top of our fibrous supramolecular membranes formed polarized monolayers, which is prerequisite for a well-functioning bioartificial kidney. In future, these supramolecular membranes allow for incorporation of peptides that may increase cell function even further.

Facile fabrication of mesoporous silica micro-jets with multi-functionalities† †Electronic supplementary information (ESI) available: Detailed BET experiments, videos and supplementary data. See DOI: 10.1039/c7nr04527a

PubMed Central

Vilela, D.; Hortelao, A. C.; Balderas-Xicohténcatl, R.; Hirscher, M.; Hahn, K.

2017-01-01

Self-propelled micro/nano-devices have been proved as powerful tools in various applications given their capability of both autonomous motion and on-demand task fulfilment. Tubular micro-jets stand out as an important member in the family of self-propelled micro/nano-devices and are widely explored with respect to their fabrication and functionalization. A few methods are currently available for the fabrication of tubular micro-jets, nevertheless there is still a demand to explore the fabrication of tubular micro-jets made of versatile materials and with the capability of multi-functionalization. Here, we present a facile strategy for the fabrication of mesoporous silica micro-jets (MSMJs) for tubular micromotors which can carry out multiple tasks depending on their functionalities. The synthesis of MSMJs does not require the use of any equipment, making it facile and cost-effective for future practical use. The MSMJs can be modified inside, outside or both with different kinds of metal nanoparticles, which provide these micromotors with a possibility of additional properties, such as the anti-bacterial effect by silver nanoparticles, or biochemical sensing based on surface enhanced Raman scattering (SERS) by gold nanoparticles. Because of the high porosity, high surface area and also the easy surface chemistry process, the MSMJs can be employed for the efficient removal of heavy metals in contaminated water, as well as for the controlled and active drug delivery, as two proof-of-concept examples of environmental and biomedical applications, respectively. Therefore, taking into account the new, simple and cheap method of fabrication, highly porous structure, and multiple functionalities, the mesoporous silica based micro-jets can serve as efficient tools for desired applications. PMID:28891580

Tissue-Engineered Heart Valve with a Tubular Leaflet Design for Minimally Invasive Transcatheter Implantation

PubMed Central

Moreira, Ricardo; Velz, Thaddaeus; Alves, Nuno; Gesche, Valentine N.; Malischewski, Axel; Schmitz-Rode, Thomas; Frese, Julia

2015-01-01

Transcatheter aortic valve implantation of (nonviable) bioprosthetic valves has been proven a valid alternative to conventional surgical implantation in patients at high or prohibitive mortality risk. In this study we present the in vitro proof-of-principle of a newly developed tissue-engineered heart valve for minimally invasive implantation, with the ultimate aim of adding the unique advantages of a living tissue with regeneration capabilities to the continuously developing transcatheter technologies. The tube-in-stent is a fibrin-based tissue-engineered valve with a tubular leaflet design. It consists of a tubular construct sewn into a self-expandable nitinol stent at three commissural attachment points and along a circumferential line so that it forms three coaptating leaflets by collapsing under diastolic back pressure. The tubular constructs were molded with fibrin and human umbilical vein cells. After 3 weeks of conditioning in a bioreactor, the valves were fully functional with unobstructed opening (systolic phase) and complete closure (diastolic phase). Tissue analysis showed a homogeneous cell distribution throughout the valve's thickness and deposition of collagen types I and III oriented along the longitudinal direction. Immunohistochemical staining against CD31 and scanning electron microscopy revealed a confluent endothelial cell layer on the surface of the valves. After harvesting, the valves underwent crimping for 20 min to simulate the catheter-based delivery. This procedure did not affect the valvular functionality in terms of orifice area during systole and complete closure during diastole. No influence on the extracellular matrix organization, as assessed by immunohistochemistry, nor on the mechanical properties was observed. These results show the potential of combining tissue engineering and minimally invasive implantation technology to obtain a living heart valve with a simple and robust tubular design for transcatheter delivery. The effect of the in vivo remodeling on the functionality of the tube-in-stent valve remains to be tested. PMID:25380414

Population analysis of the cingulum bundle using the tubular surface model for schizophrenia detection

NASA Astrophysics Data System (ADS)

Mohan, Vandana; Sundaramoorthi, Ganesh; Kubicki, Marek; Terry, Douglas; Tannenbaum, Allen

2010-03-01

We propose a novel framework for population analysis of DW-MRI data using the Tubular Surface Model. We focus on the Cingulum Bundle (CB) - a major tract for the Limbic System and the main connection of the Cingulate Gyrus, which has been associated with several aspects of Schizophrenia symptomatology. The Tubular Surface Model represents a tubular surface as a center-line with an associated radius function. It provides a natural way to sample statistics along the length of the fiber bundle and reduces the registration of fiber bundle surfaces to that of 4D curves. We apply our framework to a population of 20 subjects (10 normal, 10 schizophrenic) and obtain excellent results with neural network based classification (90% sensitivity, 95% specificity) as well as unsupervised clustering (k-means). Further, we apply statistical analysis to the feature data and characterize the discrimination ability of local regions of the CB, as a step towards localizing CB regions most relevant to Schizophrenia.

[A comparative study of the renal damage produced after the extracorporeal shock wave lithotripsy according to the lithiasis location].

PubMed

Cancho Gil, Ma J; Díz Rodríguez, R; Vírseda Chamorro, M; Alpuente Román, C; Cabrera Cabrera, J A; Paños Lozano, P

2005-04-01

The Extracorporeal shock waves lithotripsy (ESWL) is fundamental in the treatment of lithiasis. However, there are evidences that it can produce renal damage. The objective of our study is to determine the degree of affectation of the glomerular and tubular function after ESWL, and the influence of the lithiasis location on the type of renal damage. A prospective longitudinal study was carried out in 14 patients with normal renal function subjected to ESWL. We determined the basal level, and the levels at the 24 hours, at the 4th and the 10th day post ESWL of: microalbuminuria (MA) (that values the glomerular function), and N-acetyl glucosamide (NAG) and alanine aminopeptidase (AAP), (that value the tubular function). The basal levels of of MA, NAG and AAP didn't show significant differences in connection with the localization of the stones. A significant increase was observed of the three parameters only 24 hours post ESWL. No significant differences were observed between the variation of the microalbuminuria levels, AAP and NAG and the treatment in relation to the localization of the stones. It exists a glomerular and tubular damage after ESWL. This damage is not related with the pelvic or calicial location of the stones. In patient with previous normal renal function, the renal damage recovers at the 4th day post ESWL.

The Leptospira outer membrane protein LipL32 induces tubulointerstitial nephritis-mediated gene expression in mouse proximal tubule cells.

PubMed

Yang, Chih-Wei; Wu, Mai-Szu; Pan, Ming-Jeng; Hsieh, Wang-Ju; Vandewalle, Alain; Huang, Chiu-Ching

2002-08-01

Tubulointerstitial nephritis is a main renal manifestation caused by pathogenic leptospira that accumulate mostly in the proximal tubules, thereby inducing tubular injury and tubulointerstitial nephritis. To elucidate the role of leptospira outer membrane proteins in tubulointerstitial nephritis, outer membrane proteins from pathogenic Leptospira shermani and nonpathogenic Leptospira patoc extracted by Triton X-114 were administered to cultured mouse proximal tubule cells. A dose-dependent increase of monocyte chemoattractant protein-1 (MCP-1), RANTES, nitrite, and tumor necrosis factor-alpha (TNF-alpha) in the culture supernatant was observed 48 h after incubating Leptospira shermani outer membrane proteins with mouse proximal tubule cells. RT competitive-PCR experiments showed that Leptospira shermani outer membrane proteins (0.2 microg/ml) increased the expression of MCP-1, nitric oxide synthase (iNOS), RANTES, and TNF-alpha mRNA by 3.0-, 9.4-, 2.5-, and 2.5-fold, respectively, when compared with untreated cells. Outer membrane proteins extract from avirulent Leptospira patoc did not induce significant effects. The pathogenic outer membrane proteins extract contain a major component of a 32-kD lipoprotein (LipL32), which is absent in the nonpathogenic leptospira outer membrane. An antibody raised against LipL32 prevented the stimulatory effect of Leptospira shermani outer membrane proteins extract on MCP-1 and iNOS mRNA expression in cultured proximal tubule cells, whereas recombinant LipL32 significantly stimulated the expression of MCP-1 and iNOS mRNAs and augmented nuclear binding of nuclear factor-kappaB (NF-kappaB) and AP-1 transcription factors in proximal tubule cells. An antibody raised against LipL32 also blunted the effects induced by the recombinant LipL32. This study demonstrates that LipL32 is a major component of pathogenic leptospira outer membrane proteins involved in the pathogenesis of tubulointerstitial nephritis.

Functional reconstitution of rhodopsin into tubular lipid bilayers supported by nanoporous media.

PubMed

Soubias, Olivier; Polozov, Ivan V; Teague, Walter E; Yeliseev, Alexei A; Gawrisch, Klaus

2006-12-26

We report on a novel reconstitution method for G-protein-coupled receptors (GPCRs) that yields detergent-free, single, tubular membranes in porous anodic aluminum oxide (AAO) filters at concentrations sufficient for structural studies by solid-state NMR. The tubular membranes line the inner surface of pores that traverse the filters, permitting easy removal of detergents during sample preparation as well as delivery of ligands for functional studies. Reconstitution of bovine rhodopsin into AAO filters did not interfere with rhodopsin function. Photoactivation of rhodopsin in AAO pores, monitored by UV-vis spectrophotometry, was indistinguishable from rhodopsin in unsupported unilamellar liposomes. The rhodopsin in AAO pores is G-protein binding competent as shown by a [35S]GTPgammaS binding assay. The lipid-rhodopsin interaction was investigated by 2H NMR on sn-1- or sn-2-chain perdeuterated 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phospholine as a matrix lipid. Rhodopsin incorporation increased mosaic spread of bilayer orientations and contributed to spectral density of motions with correlation times in the range of nano- to microseconds, detected as a significant reduction in spin-spin relaxation times. The change in lipid chain order parameters due to interaction with rhodopsin was insignificant.

Creatinine, urea, uric acid, water and electrolytes renal handling in the healthy oldest old

PubMed Central

Musso, Carlos Guido; Álvarez Gregori, Joaquín; Jauregui, José Ricardo; Macías Núñez, Juan Florencio

2012-01-01

Renal physiology in the healthy oldest old has the following characteristics, in comparison with the renal physiology in the young: a reduced creatinine clearance, tubular pattern of creatinine back-filtration, preserved proximal tubule sodium reabsorption and uric acid secretion, reduced sodium reabsorption in the thick ascending loop of Henle, reduced free water clearance, increased urea excretion, presence of medulla hypotonicity, reduced urinary dilution and concentration capabilities, and finally a reduced collecting tubules response to furosemide which expresses a reduced potassium excretion in this segment due to a sort of aldosterone resistance. All physiological changes of the aged kidney are the same in both genders. PMID:24175249

Scaffold-Free Tubular Tissues Created by a Bio-3D Printer Undergo Remodeling and Endothelialization when Implanted in Rat Aortae

PubMed Central

Itoh, Manabu; Nakayama, Koichi; Noguchi, Ryo; Kamohara, Keiji; Furukawa, Kojirou; Uchihashi, Kazuyoshi; Toda, Shuji; Oyama, Jun-ichi; Node, Koichi; Morita, Shigeki

2015-01-01

Background Small caliber vascular prostheses are not clinically available because synthetic vascular prostheses lack endothelial cells which modulate platelet activation, leukocyte adhesion, thrombosis, and the regulation of vasomotor tone by the production of vasoactive substances. We developed a novel method to create scaffold-free tubular tissue from multicellular spheroids (MCS) using a “Bio-3D printer”-based system. This system enables the creation of pre-designed three-dimensional structures using a computer controlled robotics system. With this system, we created a tubular structure and studied its biological features. Methods and Results Using a “Bio-3D printer,” we made scaffold-free tubular tissues (inner diameter of 1.5 mm) from a total of 500 MCSs (2.5× 104 cells per one MCS) composed of human umbilical vein endothelial cells (40%), human aortic smooth muscle cells (10%), and normal human dermal fibroblasts (50%). The tubular tissues were cultured in a perfusion system and implanted into the abdominal aortas of F344 nude rats. We assessed the flow by ultrasonography and performed histological examinations on the second (n = 5) and fifth (n = 5) day after implantation. All grafts were patent and remodeling of the tubular tissues (enlargement of the lumen area and thinning of the wall) was observed. A layer of endothelial cells was confirmed five days after implantation. Conclusions The scaffold-free tubular tissues made of MCS using a Bio-3D printer underwent remodeling and endothelialization. Further studies are warranted to elucidate the underlying mechanism of endothelialization and its function, as well as the long-term results. PMID:26325298

Protective effect of 20-hydroxyeicosatetraenoic acid (20-HETE) on adriamycin-induced toxicity of human renal tubular epithelial cell (HK-2).

PubMed

Tian, Ting; Li, Jin; Wang, Meng-Ying; Xie, Xian-Fei; Li, Qi-Xiong

2012-05-15

20-Hydroxyeicosatetraenoic acid is a cytochrome P4504A11 metabolite of arachidonic acid that plays an important role in the regulation of human renal functions. In the present study, we investigated the role of 20-hydroxyeicosatetraenoic acid on adriamycin induced toxicity in human renal tubular epithelial cells. Results showed that cell viability was decreased significantly and lactate dehydrogenase activity was increased significantly in a concentration-dependent manner when human renal tubular epithelial cells were incubated with adriamycin (10⁻⁷-10⁻³ mol/l) for 24h. In contrast, 20-hydroxyeicosatetraenoic acid (0.1, 1, 10, 50 μmol/l) increased cell survival and decreased lactate dehydrogenase activity concentration dependently in human renal tubular epithelial cells. When 20-hydroxyeicosatetraenoic acid (10, 50 μmol/l) was co-administered with adriamycin (10⁻³ mol/l), it significantly increased cell viability and decreased lactate dehydrogenase activity. On the other hand, N-hydroxy-N'-(4-butyl-2-methylphenyl)formamidine (HET-0016) (1 μM), a selective inhibitor of 20-hydroxyeicosatetraenoic acid synthesizing enzyme exaggerated cell viability reduction and lactate dehydrogenase activity augmentation induced by adriamycin. Adriamycin suppressed the expression of cytochrome P4504A11 gene and its protein production in human renal tubular epithelial cells. Furthermore, adriamycin was more effective than N-hydroxy-N'-(4-butyl-2-methylphenyl)formamidine at lowering the expression of cytochrome P4504A11 gene and its protein. These results suggest that 20-hydroxyeicosatetraenoic acid may protect adriamycin-induced toxicity of human renal tubular epithelial cells, meanwhile, adriamycin-induced toxicity of human renal tubular epithelial cells possibly involves inhibiting cytochrome P4504A11 expression. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

Activating mutations in STIM1 and ORAI1 cause overlapping syndromes of tubular myopathy and congenital miosis

PubMed Central

Nesin, Vasyl; Wiley, Graham; Kousi, Maria; Ong, E-Ching; Lehmann, Thomas; Nicholl, David J.; Suri, Mohnish; Shahrizaila, Nortina; Katsanis, Nicholas; Gaffney, Patrick M.; Wierenga, Klaas J.; Tsiokas, Leonidas

2014-01-01

Signaling through the store-operated Ca2+ release-activated Ca2+ (CRAC) channel regulates critical cellular functions, including gene expression, cell growth and differentiation, and Ca2+ homeostasis. Loss-of-function mutations in the CRAC channel pore-forming protein ORAI1 or the Ca2+ sensing protein stromal interaction molecule 1 (STIM1) result in severe immune dysfunction and nonprogressive myopathy. Here, we identify gain-of-function mutations in the cytoplasmic domain of STIM1 (p.R304W) associated with thrombocytopenia, bleeding diathesis, miosis, and tubular myopathy in patients with Stormorken syndrome, and in ORAI1 (p.P245L), associated with a Stormorken-like syndrome of congenital miosis and tubular aggregate myopathy but without hematological abnormalities. Heterologous expression of STIM1 p.R304W results in constitutive activation of the CRAC channel in vitro, and spontaneous bleeding accompanied by reduced numbers of thrombocytes in zebrafish embryos, recapitulating key aspects of Stormorken syndrome. p.P245L in ORAI1 does not make a constitutively active CRAC channel, but suppresses the slow Ca2+-dependent inactivation of the CRAC channel, thus also functioning as a gain-of-function mutation. These data expand our understanding of the phenotypic spectrum of dysregulated CRAC channel signaling, advance our knowledge of the molecular function of the CRAC channel, and suggest new therapies aiming at attenuating store-operated Ca2+ entry in the treatment of patients with Stormorken syndrome and related pathologic conditions. PMID:24591628

Gonadotrophin abnormalities in an infant with Lowe syndrome.

PubMed

Warner, Bronwen E; Inward, Carol D; Burren, Christine P

2017-01-01

This case, presenting with bilateral impalpable testes, illustrates the relevance of a broad differential disorders of sex development case management. It provides new insights on hypothalamic-pituitary-gonadal (HPG) axis and testicular function abnormalities in the multisystem disorder of Lowe syndrome. Lowe syndrome, also known as oculocerebrorenal syndrome, is a rare disorder characterised by eye abnormalities, central nervous system involvement and proximal renal tubular acidosis. There are a handful of reports of pubertal delay, infertility and cryptorchidism in Lowe syndrome. Biochemistry aged 72 h: testosterone 6.4 nmol/L, LH <0.5 IU/L and FSH <0.5 IU/L. Gonadotropin-releasing hormone stimulation test identified significantly raised baseline LH = 45.4 IU/L (contrasts with earlier undetectable LH), with a 20% increase on stimulation, while baseline FSH = 4.3 IU/L with no increase on stimulation. Day 14 HCG stimulation test produced an acceptable 50% increase in testosterone. The constellation of further abnormalities suggested Lowe syndrome: hypotonia, bilateral cataracts (surgical extraction and intraocular lens implantation) and renal tubular acidosis (microscopic haematuria, hypercalciuria, proteinuria, generalised aminoaciduria, hypophosphataemia and metabolic acidosis). DNA sequencing identified de novo hemizygous frameshift mutation OCRL c.2409_2410delCT in exon 22. Interpretation of initial and repeat GnRH and HCG testing indicates the likelihood of testicular failure. Partial testicular descent occurred but left orchidopexy was required. Improving long-term gonadal function in Lowe syndrome assumes increased importance for current cohorts as advances in renal replacement therapy have greatly improved life expectancy. Noting HPG axis abnormalities in Lowe syndrome in infancy can identify cases requiring increased surveillance of pubertal progress for earlier detection and management. Clinical endocrine problems in Lowe syndrome has been reported, but has focused on abnormalities in adolescence and young adulthood: pubertal delay and infertility.We present an infant with isolated LH elevation at baseline and on GnRH stimulation testing who also had bilateral impalpable testes.Early testing of the HPG axis in patients with Lowe syndrome may help predict gonadal abnormalities from a younger age, which will enhance the overall case management into adolescence.

The early modern kidney--nephrology in and about the nineteenth century. Part 1.

PubMed

Eknoyan, Garabed

2013-01-01

The 19th century was a period of momentous scientific discoveries, technological achievements, and societal changes. A beneficiary of these revolutionary upheavals was medical empiricism that supplanted the rationalism of the past giving rise to early modern scientific medicine. Continued reliance on sensory data now magnified by technical advances generated new medical information that could be quantified with increasing precision, verified by repeated experimentation, and validated by statistical analysis. The institutionalization and integration of these methodologies into medical education were a defining step that assured their progress and perpetuation. Major advances were made in the nosography of diseases of the kidney, notably that of the diagnosis of progressive kidney disease from the presence of albuminuria by Richard Bright (1789-1858); and of renal structure and function, notably the demonstration of the continuity of the glomerular capsule with the tubular basement membrane by William Bowman (1816-1892), and the arguments for hemodynamic physical forces mediated glomerular filtration by Carl Ludwig (1816-1895) and for active tubular transport by Rudolf Heidenhain (1834-1897). Improvements in microscopy and tissue processing were instrumental in describing the cellular ultrastructure of the glomerulus and tubular segments, but their integrated function remained to be elucidated. The kidney continued to be considered a tubular secretory organ and its pathology attributed to injury of the interstitium (interstitial nephritis) or tubules (parenchymatous nephritis). © 2012 Wiley Periodicals, Inc.

Renal Type A Intercalated Cells Contain Albumin in Organelles with Aldosterone-Regulated Abundance

PubMed Central

Jensen, Thomas Buus; Cheema, Muhammad Umar; Szymiczek, Agata; Damkier, Helle Hasager; Praetorius, Jeppe

2015-01-01

Albumin has been identified in preparations of renal distal tubules and collecting ducts by mass spectrometry. This study aimed to establish whether albumin was a contaminant in those studies or actually present in the tubular cells, and if so, identify the albumin containing cells and commence exploration of the origin of the intracellular albumin. In addition to the expected proximal tubular albumin immunoreactivity, albumin was localized to mouse renal type-A intercalated cells and cells in the interstitium by three anti-albumin antibodies. Albumin did not colocalize with markers for early endosomes (EEA1), late endosomes/lysosomes (cathepsin D) or recycling endosomes (Rab11). Immuno-gold electron microscopy confirmed the presence of albumin-containing large spherical membrane associated bodies in the basal parts of intercalated cells. Message for albumin was detected in mouse renal cortex as well as in a wide variety of other tissues by RT-PCR, but was absent from isolated connecting tubules and cortical collecting ducts. Wild type I MDCK cells showed robust uptake of fluorescein-albumin from the basolateral side but not from the apical side when grown on permeable support. Only a subset of cells with low peanut agglutinin binding took up albumin. Albumin-aldosterone conjugates were also internalized from the basolateral side by MDCK cells. Aldosterone administration for 24 and 48 hours decreased albumin abundance in connecting tubules and cortical collecting ducts from mouse kidneys. We suggest that albumin is produced within the renal interstitium and taken up from the basolateral side by type-A intercalated cells by clathrin and dynamin independent pathways and speculate that the protein might act as a carrier of less water-soluble substances across the renal interstitium from the capillaries to the tubular cells. PMID:25874770

SHIP, a novel factor to ameliorate extracellular matrix accumulation via suppressing PI3K/Akt/CTGF signaling in diabetic kidney disease.

PubMed

Li, Fan; Li, Lisha; Cheng, Meijuan; Wang, Xiumin; Hao, Jun; Liu, Shuxia; Duan, Huijun

2017-01-22

Tubular interstitial extracellular matrix accumulation, which plays a key role in the pathogenesis and progression of diabetic kidney disease (DKD), is believed to be mediated by activation of PI3K/Akt signal pathway. However, it is still not clear whether SH2 domain-containing inositol 5'-phosphatase (SHIP), known as a negative regulator of PI3K/Akt pathway is also involved in extracellular matrix metabolism of diabetic kidney. In the present study, decreased SHIP and increased phospho-Akt (Ser 473, Thr 308) were found in renal tubular cells of diabetic mice accompanied by overexpression of connective tissue growth factor (CTGF) and extracellular matrix deposition versus normal mice. Again, high glucose attenuated SHIP expression in a time-dependent manner, concomitant with activation of PI3K/Akt signaling and extracellular matrix production in human renal proximal tubular epithelial cells (HK2) cultured in vitro, which was significantly prevented by transfection of M90-SHIP vector. Furthermore, in vivo delivery of rAd-INPP5D vector (SHIP expression vector) via intraperitoneal injection in diabetic mice increased SHIP expression by 3.36 times followed by 65.26%, 70.38% and 46.71% decreases of phospho-Akt (Ser 473), phospho-Akt (Thr 308) and CTGF expression versus diabetic mice receiving rAd-EGFP vector. Meanwhile, increased renal extracellular matrix accumulation of diabetic mice was also inhibited with intraperitoneal injection of rAd-INPP5D vector. These above data suggested that overexpression of SHIP might be a potent method to lessen renal extracellular matrix accumulation via inactivation of PI3K/Akt pathway and suppression of CTGF expression in DKD. Copyright © 2016 Elsevier Inc. All rights reserved.

Excess 25-hydroxyvitamin D3 exacerbates tubulointerstitial injury in mice by modulating macrophage phenotype.

PubMed

Kusunoki, Yasuo; Matsui, Isao; Hamano, Takayuki; Shimomura, Akihiro; Mori, Daisuke; Yonemoto, Sayoko; Takabatake, Yoshitsugu; Tsubakihara, Yoshiharu; St-Arnaud, René; Isaka, Yoshitaka; Rakugi, Hiromi

2015-11-01

Vitamin D hydroxylated at carbon 25 (25(OH)D) is generally recognized as a precursor of active vitamin D. Despite its low affinity for the vitamin D receptor (VDR), both deficient and excessive 25(OH)D levels are associated with poor clinical outcomes. Here we studied direct effects of 25(OH)D3 on the kidney using 25(OH)D-1α-hydroxylase (CYP27B1) knockout mice. The effects of 25(OH)D3 on unilateral ureteral obstruction were analyzed as proximal tubular cells and macrophages are two major cell types that take up 25(OH)D and contribute to the pathogenesis of kidney injury. Excess 25(OH)D3 in obstructed mice worsened oxidative stress and tubulointerstitial fibrosis, whereas moderate levels of 25(OH)D3 had no effects. The exacerbating effects of excess 25(OH)D3 were abolished in CYP27B1/VDR double-knockout mice and in macrophage-depleted CYP27B1 knockout mice. Excess 25(OH)D3 upregulated both M1 marker (TNF-α) and M2 marker (TGF-β1) levels of kidney-infiltrating macrophages. In vitro analyses verified that excess 25(OH)D3 directly upregulated TNF-α and TGF-β1 in cultured macrophages but not in tubular cells. TNF-α and 25(OH)D3 cooperatively induced oxidative stress by upregulating iNOS in tubular cells. Aggravated tubulointerstitial fibrosis in mice with excess 25(OH)D3 indicated that macrophage-derived TGF-β1 also had a key role in the pathogenesis of surplus 25(OH)D3. Thus, excess 25(OH)D3 worsens tubulointerstitial injury by modulating macrophage phenotype.

MicroRNA-375 Is Induced in Cisplatin Nephrotoxicity to Repress Hepatocyte Nuclear Factor 1-β*

PubMed Central

Hao, Jielu; Lou, Qiang; Wei, Qingqing; Mei, Shuqin; Li, Lin; Wu, Guangyu; Mi, Qing-Sheng; Mei, Changlin; Dong, Zheng

2017-01-01

Nephrotoxicity is a major adverse effect of cisplatin-mediated chemotherapy in cancer patients. The pathogenesis of cisplatin-induced nephrotoxicity remains largely unclear, making it difficult to design effective renoprotective approaches. Here, we have examined the role of microRNAs (miRNAs) in cisplatin-induced nephrotoxicity. We show that cisplatin nephrotoxicity was not affected by overall depletion of both beneficial and detrimental miRNAs from kidney proximal tubular cells in mice in which the miRNA-generating enzyme Dicer had been conditionally knocked out. To identify miRNAs involved in cisplatin nephrotoxicity, we used microarray analysis to profile miRNA expression and identified 47 up-regulated microRNAs and 20 down-regulated microRNAs in kidney cortical tissues. One up-regulated miRNA was miR-375, whose expression was also induced in cisplatin-treated renal tubular cells. Interestingly, inhibition of miR-375 decreased cisplatin-induced apoptosis, suggesting that miR-375 is a cell-damaging or pro-apoptotic agent. Blockade of P53 or NF-κB attenuated cisplatin-induced miR-375 expression, supporting a role of P53 and NF-κB in miR-375 induction. We also identified hepatocyte nuclear factor 1 homeobox B (HNF-1β) as a key downstream target of miR-375. Of note, we further demonstrated that HNF-1β protected renal cells against cisplatin-induced apoptosis. Together, these results suggest that upon cisplatin exposure, P53 and NF-κB collaboratively induce miR-375 expression, which, in turn, represses HNF-1β activity, resulting in renal tubular cell apoptosis and nephrotoxicity. PMID:28119452

Recombinant human GLP-1(rhGLP-1) alleviating renal tubulointestitial injury in diabetic STZ-induced rats.

PubMed

Yin, Weiqin; Xu, Shiqing; Wang, Zai; Liu, Honglin; Peng, Liang; Fang, Qing; Deng, Tingting; Zhang, Wenjian; Lou, Jinning

2018-01-01

GLP-1-based treatment improves glycemia through stimulation of insulin secretion and inhibition of glucagon secretion. Recently, more and more findings showed that GLP-1 could also protect kidney from diabetic nephropathy. Most of these studies focused on glomeruli, but the effect of GLP-1 on tubulointerstitial and tubule is not clear yet. In this study, we examined the renoprotective effect of recombinant human GLP-1 (rhGLP-1), and investigated the influence of GLP-1 on inflammation and tubulointerstitial injury using diabetic nephropathy rats model of STZ-induced. The results showed that rhGLP-1 reduced urinary albumin without influencing the body weight and food intake. rhGLP-1 could increased the serum C-peptide slightly but not lower fasting blood glucose significantly. In diabetic nephropathy rats, beside glomerular sclerosis, tubulointerstitial fibrosis was very serious. These lesions could be alleviated by rhGLP-1. rhGLP-1 decreased the expression of profibrotic factors collagen I, α-SMA, fibronectin, and inflammation factors MCP-1 and TNFα in tubular tissue and human proximal tubular cells (HK-2 cells). Furthermore, rhGLP-1 significantly inhibited the phosphorylation of NF-κB, MAPK in both diabetic tubular tissue and HK-2 cells. The inhibition of the expression of TNFα, MCP-1, collagen I and α-SMA in HK-2 cells by GLP-1 could be mimicked by blocking NF-κB or MAPK. These results indicate that rhGLP-1 exhibit renoprotective effect by alleviation of tubulointerstitial injury via inhibiting phosphorylation of MAPK and NF-κB. Therefore, rhGLP-1 may be a potential drug for treatment of diabetic nephropathy. Copyright © 2017 Elsevier Inc. All rights reserved.

Bone Resorption and Environmental Exposure to Cadmium in Women: A Population Study

PubMed Central

Schutte, Rudolph; Nawrot, Tim S.; Richart, Tom; Thijs, Lutgarde; Vanderschueren, Dirk; Kuznetsova, Tatiana; Van Hecke, Etienne; Roels, Harry A.; Staessen, Jan A.

2008-01-01

Background Environmental exposure to cadmium decreases bone density indirectly through hypercalciuria resulting from renal tubular dysfunction. Objective We sought evidence for a direct osteotoxic effect of cadmium in women. Methods We randomly recruited 294 women (mean age, 49.2 years) from a Flemish population with environmental cadmium exposure. We measured 24-hr urinary cadmium and blood cadmium as indexes of lifetime and recent exposure, respectively. We assessed the multivariate-adjusted association of exposure with specific markers of bone resorption, urinary hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP), as well as with calcium excretion, various calciotropic hormones, and forearm bone density. Results In all women, the effect sizes associated with a doubling of lifetime exposure were 8.4% (p = 0.009) for HP, 6.9% (p = 0.10) for LP, 0.77 mmol/day (p = 0.003) for urinary calcium, –0.009 g/cm2 (p = 0.055) for proximal forearm bone density, and –16.8% (p = 0.065) for serum parathyroid hormone. In 144 postmenopausal women, the corresponding effect sizes were –0.01223 g/cm2 (p = 0.008) for distal forearm bone density, 4.7% (p = 0.064) for serum calcitonin, and 10.2% for bone-specific alkaline phosphatase. In all women, the effect sizes associated with a doubling of recent exposure were 7.2% (p = 0.001) for urinary HP, 7.2% (p = 0.021) for urinary LP, –9.0% (p = 0.097) for serum parathyroid hormone, and 5.5% (p = 0.008) for serum calcitonin. Only one woman had renal tubular dysfunction (urinary retinol-binding protein > 338 μg/day). Conclusions In the absence of renal tubular dysfunction, environmental exposure to cadmium increases bone resorption in women, suggesting a direct osteotoxic effect with increased calciuria and reactive changes in calciotropic hormones. PMID:18560534

Albumin Overload and PINK1/Parkin Signaling-Related Mitophagy in Renal Tubular Epithelial Cells.

PubMed

Tan, Jin; Xie, Qi; Song, Shuling; Miao, Yuyang; Zhang, Qiang

2018-03-01

BACKGROUND Albumin, as a major urinary protein component, is a risk factor for chronic kidney disease progression. Mitochondrial dysfunction is one of the main causes of albumin-induced proximal tubule cells injury. Mitophagy is considered as a pivotal protective mechanism for the elimination of dysfunctional mitochondria. The objective of this research was to determine whether albumin overload-induced mitochondrial dysfunction can activate PINK1/Parkin-mediated mitophagy in renal tubular epithelial cells (TECs). MATERIAL AND METHODS Immunofluorescence assay and Western blot assay were used to detect the effects of albumin overload on autophagy marker protein LC3. Transmission electron microscopy and Western blot assay were used to investigate the role of albumin in mitochondrial injury. Western blot assay and co-localization of acidic lysosomes and mitochondria assay were employed to detect the activation of mitophagy induced by albumin. Finally, we explored the role of PINK1/Parkin signaling in albumin-induced mitophagy by inhibiting mitophagy by knockdown of PARK2 (Parkin) level. RESULTS Immunofluorescence and Western blot results showed that the expression level of LC3-II increased, and the maximum increase point was observed after 8 h of albumin treatment. Transmission electron microscopy results demonstrated that albumin overload-induced mitochondrial injury and quantity of autophagosomes increased. Additionally, expression of PINK1 and cytosolic cytochrome C increased and mitochondria cytochrome C decreased in the albumin group. The co-localization of acidic lysosomes and mitochondria demonstrated that the number of albumin overload-induced mitophagy-positive dots increased. The transient transfection of PARK2 siRNA result showed knockdown of the expression level of PARK2 can inhibit mitophagy induced by albumin. CONCLUSIONS In conclusion, our study suggests that mitochondrial dysfunction activates the PINK1/Parkin signaling and mitophagy in renal tubular epithelial cells under albumin overload condition.

Phosphate uptake by a kidney cell line (LLC-PK1).

PubMed

Rabito, C A

1983-07-01

The uptake of inorganic phosphate was studied in an epithelial cell line of renal origin. Phosphate was accumulated through a mechanism with several features of a carrier-mediated process. The influx was accounted for by a saturable Na+-dependent and a nonsaturable Na+-independent process. Kinetic analysis at pH 6.6 and 7.4 suggests that the dibasic form of phosphate is the form transported by the saturable Na+-dependent system. The presence of Na+ in the incubation medium increased Vmax without affecting Km. Arsenate competitively inhibited the Na+-dependent phosphate transport with a Ki of 1.2 mM at 140 mM Na+ and pH 7.4. Other known inhibitors of phosphate reabsorption in the proximal tubule also inhibited phosphate transport by this cell line. Uptake studies from either side of the monolayers indicated that this transport system is preferentially located in the apical membrane of the cultured renal cells. These results show a close similarity between the Na+-dependent phosphate transport system in LLC-PK1 cells and the system present in the apical membrane of the proximal tubular cells.

Reactor pressure vessel nozzle

DOEpatents

Challberg, Roy C.; Upton, Hubert A.

1994-01-01

A nozzle for joining a pool of water to a nuclear reactor pressure vessel includes a tubular body having a proximal end joinable to the pressure vessel and a distal end joinable in flow communication with the pool. The body includes a flow passage therethrough having in serial flow communication a first port at the distal end, a throat spaced axially from the first port, a conical channel extending axially from the throat, and a second port at the proximal end which is joinable in flow communication with the pressure vessel. The inner diameter of the flow passage decreases from the first port to the throat and then increases along the conical channel to the second port. In this way, the conical channel acts as a diverging channel or diffuser in the forward flow direction from the first port to the second port for recovering pressure due to the flow restriction provided by the throat. In the backflow direction from the second port to the first port, the conical channel is a converging channel and with the abrupt increase in flow area from the throat to the first port collectively increase resistance to flow therethrough.

Comparative Characterization of Shiga Toxin Type 2 and Subtilase Cytotoxin Effects on Human Renal Epithelial and Endothelial Cells Grown in Monolayer and Bilayer Conditions.

PubMed

Álvarez, Romina S; Sacerdoti, Flavia; Jancic, Carolina; Paton, Adrienne W; Paton, James C; Ibarra, Cristina; Amaral, María M

2016-01-01

Postdiarrheal hemolytic uremic syndrome (HUS) affects children under 5 years old and is responsible for the development of acute and chronic renal failure, particularly in Argentina. This pathology is a complication of Shiga toxin (Stx)-producing Escherichia coli infection and renal damage is attributed to Stx types 1 and 2 (Stx1, Stx2) produced by Escherichia coli O157:H7 and many other STEC serotypes. It has been reported the production of Subtilase cytotoxin (SubAB) by non-O157 STEC isolated from cases of childhood diarrhea. Therefore, it is proposed that SubAB may contribute to HUS pathogenesis. The human kidney is the most affected organ because very Stx-sensitive cells express high amounts of biologically active receptor. In this study, we investigated the effects of Stx2 and SubAB on primary cultures of human glomerular endothelial cells (HGEC) and on a human tubular epithelial cell line (HK-2) in monoculture and coculture conditions. We have established the coculture as a human renal proximal tubule model to study water absorption and cytotoxicity in the presence of Stx2 and SubAB. We obtained and characterized cocultures of HGEC and HK-2. Under basal conditions, HGEC monolayers exhibited the lowest electrical resistance (TEER) and the highest water permeability, while the HGEC/HK-2 bilayers showed the highest TEER and the lowest water permeability. In addition, at times as short as 20-30 minutes, Stx2 and SubAB caused the inhibition of water absorption across HK-2 and HGEC monolayers and this effect was not related to a decrease in cell viability. However, toxins did not have inhibitory effects on water movement across HGEC/HK-2 bilayers. After 72 h, Stx2 inhibited the cell viability of HGEC and HK-2 monolayers, but these effects were attenuated in HGEC/HK-2 bilayers. On the other hand, SubAB cytotoxicity shows a tendency to be attenuated by the bilayers. Our data provide evidence about the different effects of these toxins on the bilayers respect to the monolayers. This in vitro model of communication between human renal microvascular endothelial cells and human proximal tubular epithelial cells is a representative model of the human proximal tubule to study the effects of Stx2 and SubAB related to the development of HUS.

Glomerular and Tubular Renal Function after Repeated Once-Daily Tobramycin Courses in Cystic Fibrosis Patients.

PubMed

Stehling, Florian; Büscher, Rainer; Grosse-Onnebrink, Jörg; Hoyer, Peter F; Mellies, Uwe

2017-01-01

Introduction . Antibiotic treatment regimens against Pseudomonas aeruginosa lung infection in cystic fibrosis (CF) patients often include aminoglycoside antibiotics that may cause chronic renal failure after repeated courses. Aminoaciduria is an early marker of acute aminoglycoside-induced renal tubular dysfunction. We hypothesized that urinary amino acid reabsorption is decreased after repeated once-daily tobramycin therapies. Methods . In this prospective cross-sectional study creatinine clearance was estimated by the Schwartz and the Cockcroft-Gault formula. Tubular amino acid reabsorption was determined by ion exchange chromatography in 46 patients with CF who received multiple tobramycin courses (6.3 ± 10.1 (1-57)) in a once-daily dosing regimen and 10 who did not. Results . Estimated creatinine clearance employing the Cockcroft-Gault was mildly reduced in 17/46 (37%) of the patients who received tobramycin and 5/10 (50%) of the patients who did not but in none using the Schwartz formula. No association with lifetime tobramycin courses was found. Tubular amino acid reabsorption was not influenced by the amount of once-daily tobramycin courses. Conclusion . Clinically not significant reduction of eCCL occurred in a minority of CF patients. However, chronic tubular dysfunction was not present in patients with CF repeatedly treated with tobramycin in the once-daily dosing scheme.

Characterizing the interactions of organic nanoparticles with renal epithelial cells in vivo.

PubMed

Nair, Anil V; Keliher, Edmund J; Core, Amanda B; Brown, Dennis; Weissleder, Ralph

2015-01-01

Nanotechnology approaches are actively being pursued for drug delivery, novel diagnostics, implantable devices, and consumer products. While considerable research has been performed on the effects of these materials on targeted tumor or phagocytic cells, relatively little is known about their effects on renal cells. This becomes critical for supersmall nanoparticles (<10 nm), designed to be renally excreted. The active endocytic machinery of kidney proximal tubules avidly internalizes filtered proteins, which may also be the case for filtered nanoparticles. To test whether such interactions affect kidney function, we injected mice with either 5 nm dextran-based nanoparticles (DNP) that are similar in composition to FDA-approved materials or poly(amido amine) dendrimer nanoparticles (PNP) of comparable size. These fluorescently tagged nanoparticles were both filtered and internalized by renal tubular epithelial cells in a dose- and time-dependent fashion. The biological effects were quantitated by immunocytochemistry, measuring kidney injury markers and performing functional tests. DNP administration resulted in a dose-dependent increase in urinary output, while cellular albumin endocytosis was increased. The expression of megalin, a receptor involved in albumin uptake, was also increased, but AQP1 expression was unaffected. The effects after PNP administration were similar but additionally resulted in increased clathrin expression and increased endocytosis of dextran. We conclude that there are no major detrimental renal effects of DNP on overall kidney function, but changes in endocytosis-mediating protein expression do occur. These studies provide a framework for the testing of additional nanoparticle preparations as they become available.

The eyes of mesopelagic crustaceans. III. Thysanopoda tricuspidata (Euphausiacea).

PubMed

Meyer-Rochow, V B; Walsh, S

1978-12-14

The compound eyes of the mesopelagic eupausiid Thysanopoda tricuspidata were investigated by light-, scanning-, and transmission electron microscopy. The eyes are spherical and have a diameter that corresponds to 1/6 of the carapace length. The hexagonal facets have strongly curved outer surfaces. Although there are four crystalline cone cells, only two participate in the formation of the cone, which is 90-120 micrometer long and appears to have a radial gradient of refractive index. The clear zone, separating dioptric structures and retinula, is only 90-120 micrometer wide. In it lie the very large oval nuclei of the seven retinula cells. Directly in front of the 70 micrometer long and 15 micrometer thick rhabdom a lens-like structure of 12 micrometer diameter is developed. This structure, known in only a very few arthropods, seems to be present in all species of Euphausiacea studied to date. It is believed that the rhabdom lens improves near-field vision and absolute light sensitivity. Rod-shaped pigment grains and mitochondria of the tubular type are found in the plasma of retinula cells. The position of the proximal screening pigment as well as the microvillar organization in the rhabdom are indicative of light-adapted material. The orthogonal alignment of rhabdovilli suggests polarization sensitivity. Behind each rabdom there is a cup-shaped homogenous structure of unknown, but possibly optical function. Finally, the structure and the function of the euphysiid eye are reviewed and the functional implications of individual components are discussed.

Ultrastructural differentiation of sperm tail region in Diplometopon zarudnyi (an amphisbaenian reptile)

PubMed Central

Al-Dokhi, O.; Mukhtar, Ahmed; Al-Dosary, A.; Al-Sadoon, M.K.

2015-01-01

Diplometopon zarudnyi, a worm lizard belongs to amphisbaenia under trogonophidae family. This species exists in limited areas of the Arabian Peninsula and is an oscillating digger found in sub-surface soils. The present study aimed to investigate the sperm tail differentiation in D. zarudnyi. Ten male adults of D. zarudnyi were collected from Riyadh during April–May 2011. To study the sperm tail at the ultrastructural level the testes were fixed in 3% glutaraldehyde, than post fixed in 1% osmium tetaroxide followed by dehydration in ethanol grades; samples were cleared in propylene oxide and embedded in resin. Tail formation begins by the moving of centrioles and mitochondria towards the posterior pole of sperm head. Simultaneously many microtubules of the midpiece axoneme were enclosed by a thick layer of granular material. Mitochondria of midpiece lie alongside the proximal centriole which forms a very short neck region and possess tubular cristae internally and concentric layers of cristae superficially. During this course a fibrous sheath surrounds the axoneme of mid and principal piece. At the end dissolution of longitudinal manchette takes place. The mitochondria then rearrange themselves around the proximal and distal centrioles to form a neck region. Later, the fibrous sheath surrounds the proximal portion of the flagella. This part along with sperm head of D. zarudnyi provides a classical model that could be used in future for evolutionary and phylogenetic purposes of class reptilia. PMID:26155090

Experimental study of the flow in the wake of a stationary sphere immersed in a turbulent boundary layer

NASA Astrophysics Data System (ADS)

van Hout, René; Eisma, Jerke; Elsinga, Gerrit E.; Westerweel, Jerry

2018-02-01

In many applications, finite-sized particles are immersed in a turbulent boundary layer (TBL) and it is of interest to study wall effects on the instantaneous shedding of turbulence structures and associated mean velocity and Reynolds stress distributions. Here, 3D flow field dynamics in the wake of a prototypical, small sphere (D+=50 , 692

Effect of Organophosphate Compounds on Renal Function and Transport.

DTIC Science & Technology

1983-09-15

DiBona , 15) have presented physiological data that suggest a direct role of the sympathetic nerves in renal tubular sodium reabsorption, i.e., not...tubular sodium reabsorp- tion. Amer. J. Physiol., 233 (1977) F73-81. 16. G.F. DiBona , 1.3. Zambraski, A.S. Aquilera and G.3. Kaloyanides, Neurogenic...reflex renal nerve stimulation. J. Pharuacol. Exptl. flerap.. 198 (1976a) 464-472. 29. 1.3. Zambraski, G.E. DiBona and 0.3. Kloyanides, Specificity of

Cisplatin-induced cytotoxicity in BSO-exposed renal proximal tubular epithelial cells: sex, age, and species.

PubMed

Lu, Yongke; Kawashima, Akira; Horii, Ikuo; Zhong, Laifu

2005-01-01

Cisplatin (CP)-induced kidney damage and effects of DL-buthionine-(S,R)-sulfoximine (BSO) on it are species- and age-different. It remains unclear whether CP-induced cytotoxicity in renal proximal tubular epithelial cells (RTEC), the main target cells of CP, is also species- and age-different; and whether CP-induced cytotoxicity varies with the difference in age and species, if any, is one of the questions. In the present study, the effects of BSO on CP-induced cytotoxicity in primary cultures of RTEC isolated from monkeys and different age and sex rats were studied. The RTEC were isolated from 3-week-old, 2-month-old, or 5-month-old rats, and 6-8 year-old monkeys. After subculturing, RTEC was inoculated into type I collagen-coated 96-well culture plates; after preincubation, 40 microM BSO was added, 16 hours later, varying concentrations of CP were added. At that time, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays were performed to test cell viability. The concentrations of CP that inhibited 50% cell growth (IC50) of RTEC from rats and monkeys were 1.11 and 3.03 mM at 8 hours, and 0.51 and 1.24 mM at 24 hours, respectively. The BSO made the IC50s of RTEC from rats and monkeys lower, down to 0.07 and 0.48 mM at 8 hours, and 0.02 and 0.11 mM at 24 hours, respectively. The IC50s of RTEC from different sex and age rats were almost same. These results suggested that CP-induced cytotoxicity was concentration- and time-dependent, with species-dependent differences, rat RTEC were more susceptible to CP than monkey RTEC, rat RTEC were more dependent on glutathione (GSH) during the stress state were than monkey cells; CP-induced cytotoxicity was without sex- and age-dependent differences in rat RTEC.

Role of 2',3'-cyclic nucleotide 3'-phosphodiesterase in the renal 2',3'-cAMP-adenosine pathway.

PubMed

Jackson, Edwin K; Gillespie, Delbert G; Mi, Zaichuan; Cheng, Dongmei; Bansal, Rashmi; Janesko-Feldman, Keri; Kochanek, Patrick M

2014-07-01

Energy depletion increases the renal production of 2',3'-cAMP (a positional isomer of 3',5'-cAMP that opens mitochondrial permeability transition pores) and 2',3'-cAMP is converted to 2'-AMP and 3'-AMP, which in turn are metabolized to adenosine. Because the enzymes involved in this "2',3'-cAMP-adenosine pathway" are unknown, we examined whether 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) participates in the renal metabolism of 2',3'-cAMP. Western blotting and real-time PCR demonstrated expression of CNPase in rat glomerular mesangial, preglomerular vascular smooth muscle and endothelial, proximal tubular, thick ascending limb and collecting duct cells. Real-time PCR established the expression of CNPase in human glomerular mesangial, proximal tubular and vascular smooth muscle cells; and the level of expression of CNPase was greater than that for phosphodiesterase 4 (major enzyme for the metabolism of 3',5'-cAMP). Overexpression of CNPase in rat preglomerular vascular smooth muscle cells increased the metabolism of exogenous 2',3'-cAMP to 2'-AMP. Infusions of 2',3'-cAMP into isolated CNPase wild-type (+/+) kidneys increased renal venous 2'-AMP, and this response was diminished by 63% in CNPase knockout (-/-) kidneys, whereas the conversion of 3',5'-cAMP to 5'-AMP was similar in CNPase +/+ vs. -/- kidneys. In CNPase +/+ kidneys, energy depletion (metabolic poisons) increased kidney tissue levels of adenosine and its metabolites (inosine, hypoxanthine, xanthine, and uric acid) without accumulation of 2',3'-cAMP. In contrast, in CNPase -/- kidneys, energy depletion increased kidney tissue levels of 2',3'-cAMP and abolished the increase in adenosine and its metabolites. In conclusion, kidneys express CNPase, and renal CNPase mediates in part the renal 2',3'-cAMP-adenosine pathway. Copyright © 2014 the American Physiological Society.

Evaluation of novel biomarkers of nephrotoxicity in Cynomolgus monkeys treated with gentamicin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gautier, Jean-Charles, E-mail: jean-charles.gautie

Most studies to evaluate kidney safety biomarkers have been performed in rats. This study was conducted in Cynomolgus monkeys in order to evaluate the potential usefulness of novel biomarkers of nephrotoxicity in this species. Groups of 3 males were given daily intramuscular injections of gentamicin, a nephrotoxic agent known to produce lesions in proximal tubules, at dose-levels of 10, 25, or 50 mg/kg/day for 10 days. Blood and 16-h urine samples were collected on Days − 7, − 3, 2, 4, 7, and at the end of the dosing period. Several novel kidney safety biomarkers were evaluated, with single- andmore » multiplex immunoassays and in immunoprecipitation-LC/MS assays, in parallel to histopathology and conventional clinical pathology parameters. Treatment with gentamicin induced a dose-dependent increase in kidney tubular cell degeneration/necrosis, ranging from minimal to mild severity at 10 mg/kg/day, moderate at 25 mg/kg/day, and to severe at 50 mg/kg/day. The results showed that the novel urinary biomarkers, microalbumin, α1-microglobulin, clusterin, and osteopontin, together with the more traditional clinical pathology parameters, urinary total protein and N-acetyl-β-D-glucosaminidase (NAG), were more sensitive than blood urea nitrogen (BUN) and serum creatinine (sCr) to detect kidney injury in the monkeys given 10 mg/kg/day gentamicin for 10 days, a dose leading to an exposure which is slightly higher than the desired therapeutic exposure in clinics. Therefore, these urinary biomarkers represent non-invasive biomarkers of proximal tubule injury in Cynomolgus monkeys which may be potentially useful in humans. - Highlights: • Gentamicin induced kidney tubular cell degeneration/necrosis in Cynomolgus monkey • Urinary clusterin and osteopontin were sensitive biomarkers of kidney injury. • Microalbumin and α1-microglobulin in urine were also more sensitive than serum creatinine.« less

Downregulation of cell survival signalling pathways and increased cell damage in hydrogen peroxide-treated human renal proximal tubular cells by alpha-erythropoietin.

PubMed

Andreucci, M; Fuiano, G; Presta, P; Lucisano, G; Leone, F; Fuiano, L; Bisesti, V; Esposito, P; Russo, D; Memoli, B; Faga, T; Michael, A

2009-08-01

Erythropoietin has been shown to have a protective effect in certain models of ischaemia-reperfusion, and in some cases the protection has been correlated with activation of signalling pathways known to play a role in cell survival and proliferation. We have studied whether erythropoietin would overcome direct toxic effects of hydrogen peroxide (H(2)O(2)) treatment to human renal proximal tubular (HK-2) cells. HK-2 cells were incubated with H(2)O(2) (2 mm) for 2 h with or without erythropoietin at concentrations of 100 and 400 U/ml, and cell viability/proliferation was assessed by chemical reduction of MTT. Changes in phosphorylation state of the kinases Akt, glycogen synthase kinase-3beta (GSK-3beta), mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase 1 and 2 (ERK1/ERK2) were also analysed. Cells incubated with H(2)O(2) alone showed a significant decrease in viability, which did not significantly change by addition of erythropoietin at concentration of 100 U/ml, but was further reduced when concentration of erythropoietin was increased to 400 U/ml. Phosphorylation state of the kinases Akt, GSK-3beta, mTOR and ERK1/ERK2 of H(2)O(2)-treated HK-2 cells was slightly altered in the presence of erythropoietin at concentration of 100 U/ml, but was significantly less in the presence of erythropoietin at a concentration of 400 U/ml. Phosphorylation of forkhead transcription factor FKHRL1 was diminished in cells incubated with H(2)O(2) and erythropoietin at a concentration of 400 U/ml. Erythropoietin, at high concentrations, may significantly increase cellular damage in HK-2 cells subjected to oxidative stress, which may be due in part to decrease in activation of important signalling pathways involved in cell survival and/or cell proliferation.

Protective Effects of Pistacia lentiscus L. fruit extract against calcium oxalate monohydrate induced proximal tubular injury.

PubMed

Cheraft-Bahloul, Nassima; Husson, Cécile; Ourtioualous, Meriam; Sinaeve, Sébastien; Atmani, Djebbar; Stévigny, Caroline; Nortier, Joëlle L; Antoine, Marie-Hélène

2017-09-14

The world prevalence of kidney stones is increasing and plants are frequently used to treat urolithiasis. Pistacia lentiscus L, a plant which freely grows around the Mediterranean basin areas, is widely used for various pathologies. P. lentiscus has an important impact as it has economical value on top of its pharmacological interest. Decoctions of its aerial parts and/or resin are used to treat kidney stones. To in vitro assess the potential nephroprotective effect of Pistacia lentiscus ethanolic fruit extract (PLEF) on proximal tubular cells in response to the adhesion of calcium oxalate monohydrate (COM) crystals. Human Kidney [HK]-2 cells were incubated with and without COM in the presence or absence of PLEF. Cell viability was measured by the resazurin assay. The expression of E-cadherin was analyzed by PCR. The extracellular production of H 2 O 2 was measured by Amplex® Red H 2 O 2 Assay. The numbers of detached or non-adherent COM crystals in the presence of PLEF were microscopically captured and counted using ImageJ software. The interaction of PLEF with COM and the effect of PLEF on crystal size were analyzed by flow cytometry. The spectrophotometric measurement of turbidity was performed for assessing the COM concentration. PLEF incubated with COM was able to increase the cell viability. The decrease of E-cadherin expression after incubation with COM was counteracted by PLEF. Overproduction of H 2 O 2 induced by COM was also inhibited by PLEF. Observations using flow cytometry showed that interactions between PLEF and the COM crystals occurred. PLEF was also effective in reducing the particles size and in lowering COM concentration. Our data show that COM tubulotoxicity can be significantly reversed by PLEF -at least in part- via an inhibition of COM crystals adhesion onto the apical membrane. This early beneficial effect of PLEF needs to be further investigated as a useful strategy in nephrolithiasis prevention. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

Handling of the homocysteine S-conjugate of methylmercury by renal epithelial cells: role of organic anion transporter 1 and amino acid transporters.

PubMed

Zalups, Rudolfs K; Ahmad, Sarfaraz

2005-11-01

Recently, the activity of the organic anion transporter 1 (OAT1) protein has been implicated in the basolateral uptake of inorganic mercuric species in renal proximal tubular cells. Unfortunately, very little is known about the role of OAT1 in the renal epithelial transport of organic forms of mercury, such as methylmercury (CH(3)Hg(+)). Homocysteine (Hcy) S-conjugates of methylmercury [(S)-(3-amino-3-carboxypropylthio)(methyl)mercury (CH(3)Hg-Hcy)] have been identified recently as being potentially important biologically relevant forms of mercury. Thus, the present study was designed to characterize the transport of CH(3)Hg-Hcy in Madin-Darby canine kidney (MDCK) cells (which are derived from the distal nephron) that were transfected stably with the human isoform of OAT1 (hOAT1). Data on saturation kinetics, time dependence, substrate specificity, and temperature dependence demonstrated that CH(3)Hg-Hcy is a transportable substrate of hOAT1. However, substrate-specificity data from the control MDCK cells also showed that CH(3)Hg-Hcy is a substrate of one or more transporter(s) that is/are not hOAT1. Additional findings indicated that at least one amino acid transport system was probably responsible for this transport. It is noteworthy that the activity of amino acid transporters accounted for the greatest level of uptake of CH(3)Hg-Hcy in the hOAT1-expressing cells. Furthermore, rates of survival of the hOAT1-transfected MDCK cells were significantly lower than those of corresponding control MDCK cells when they were exposed to cytotoxic concentrations of CH(3)Hg-Hcy. Collectively, the present data indicate that CH(3)Hg-Hcy is a transportable substrate of OAT1 and amino acid transporters and, thus, is probably a transportable mercuric species taken up in vivo by proximal tubular epithelial cells.

Reversal of radiocontrast medium toxicity in human renal proximal tubular cells by white grape juice extract.

PubMed

Andreucci, Michele; Faga, Teresa; Pisani, Antonio; Sabbatini, Massimo; Russo, Domenico; Mattivi, Fulvio; De Sarro, Giovambattista; Navarra, Michele; Michael, Ashour

2015-03-05

Radiocontrast media (RCM)-induced nephrotoxicity (CIN) is a major clinical problem accounting for 12% of all hospital-acquired cases of acute kidney injury. The pathophysiology of CIN is not well understood, but direct toxic effects on renal cells have been postulated as contributing to CIN. We have investigated the effect of a white grape (Vitis vinifera) juice extract (WGJe) on human renal proximal tubular (HK-2) cells treated with the radiocontrast medium (RCM) sodium diatrizoate. WGJe caused an increase in phosphorylation of the prosurvival kinases Akt and ERK1/2 in HK-2 cells. Treatment of HK-2 cells with 75 mgI/ml sodium diatrizoate for 2.5h and then further incubation (for 27.5h) after removal of the RCM caused a drastic decrease in cell viability. However, pre-treatment with WGJe, prior to incubation with diatrizoate, dramatically improved cell viability. Analysis of key signaling molecules by Western blotting showed that diatrizoate caused a drastic decrease in phosphorylation of Akt (Ser473), FOXO1 (Thr24) and FOXO3a (Thr32) during the initial 2.5h incubation period, and WGJe pre-treatment caused a reversal of these effects. Further analysis by Western blotting of samples from HK-2 cells cultured for longer periods of time (for up to 27.5h after an initial 2.5h exposure to diatrizoate with or without WGJe pre-treatment) showed that WGJe pre-treatment caused a negative effect on phosphorylation of p38, NF-κB (Ser276) and pERK1/2 whilst having a positive effect on the phosphorylation of Akt, FOXO1/FOXO3a and maintained levels of Pim-1 kinase. WGJe may alleviate RCM toxicity through modulation of signaling molecules that are known to be involved in cell death and cell survival and its possible beneficial effects should be further investigated. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Independent cellular effects of cold ischemia and reperfusion: experimental molecular study.

PubMed

Lledó-García, E; Humanes-Sánchez, B; Mojena-Sánchez, M; Rodrígez, J C J; Hernández-Fernández, C; Tejedor-Jorge, A; Fernández, A L

2013-04-01

There is less information available on cell cultures on the exclusive effects of either duration of cold ischemia (CI) or rewarming-reperfusion in the kidney subjected to initial warm ischemia (WI). Therefore, the goals of our work were: (1) to evaluate the consequences on tubular cellular viability of different durations of CI on a kidney after an initial period of WI, and (2) to analyze the additional effect on tubular cell viability of rewarming of the same kidney. Sixteen mini-pig were used. All the animals were performed a right nephrectomy after 45-minute occlusion of the vascular pedicle. The kidneys were then divided into 2 groups (phase 1): cold storage in university of wisconsin (UW) solution for 3 hours (group A, n = 8) at 4°C, or cold storage in UW for 12 hours (group B, n = 8) at 4°C. Four organs of group A and four organs of group B were autotrasplanted (AT) and reperfused for 1 hour (phase 2). Nephrectomy was finally done. Biopsies were taken from all groups to perform cultures of proximal tubule epithelium cells. The biopsies were subjected to studies of cellular morphological viability (contrast phase microscopy [CPM]) and quantitative (confluence cell [CC]) parameters. Phase of pure CI effects (phase 1): Both CC rate and CPM parameters were significantly lower in group B compared with group A, where cell activity reached almost normal results. Phase of CI + AT (phase 2): At produced additional harmful effects in cell cultures compared with those obtained in phase 1, more evident in group B cells. The presence of cold storage followed by rewarming-reperfusion induces independent and cumulative detrimental effects in viability of renal proximal tubule cells. CI periods ≤ 3 hours may ameliorate the injuries secondary to reperfusion in comparison with longer CI periods. Copyright © 2013 Elsevier Inc. All rights reserved.

Enhanced Flexible Tubular Microelectrode with Conducting Polymer for Multi-Functional Implantable Tissue-Machine Interface

NASA Astrophysics Data System (ADS)

Tian, Hong-Chang; Liu, Jing-Quan; Kang, Xiao-Yang; Tang, Long-Jun; Wang, Ming-Hao; Ji, Bo-Wen; Yang, Bin; Wang, Xiao-Lin; Chen, Xiang; Yang, Chun-Sheng

2016-05-01

Implantable biomedical microdevices enable the restoration of body function and improvement of health condition. As the interface between artificial machines and natural tissue, various kinds of microelectrodes with high density and tiny size were developed to undertake precise and complex medical tasks through electrical stimulation and electrophysiological recording. However, if only the electrical interaction existed between electrodes and muscle or nerve tissue without nutrition factor delivery, it would eventually lead to a significant symptom of denervation-induced skeletal muscle atrophy. In this paper, we developed a novel flexible tubular microelectrode integrated with fluidic drug delivery channel for dynamic tissue implant. First, the whole microelectrode was made of biocompatible polymers, which could avoid the drawbacks of the stiff microelectrodes that are easy to be broken and damage tissue. Moreover, the microelectrode sites were circumferentially distributed on the surface of polymer microtube in three dimensions, which would be beneficial to the spatial selectivity. Finally, the in vivo results confirmed that our implantable tubular microelectrodes were suitable for dynamic electrophysiological recording and simultaneous fluidic drug delivery, and the electrode performance was further enhanced by the conducting polymer modification.

Experimental drug-induced changes in renal function and biodistribution of /sup 99m/Tc-MDP

DOE Office of Scientific and Technical Information (OSTI.GOV)

McAfee, J.G.; Singh, A.; Roskopf, M.

Increased renal uptake of /sup 99m/Tc methylene diphosphonate (MDP) was observed irregularly in rats after methotrexate, vincristine or gentamicin, administered separately. Cisplatin regularly induced a dose-related increased MDP uptake which correlated with the degree of tubular damage histologically. The augmented MDP renal uptake was not consistently accompanied by a decreased clearance of simultaneously injected I-131 Hippuran, particularly at lower drug dose levels. This observation agreed with previous evidence that the mechanisms of tubular transport of diphosphonates and organic acids like Hippuran are different. At higher dose levels, the augmented MDP uptake was accompanied by increased renal calcium, hypophosphatemia, elevated serummore » urea nitrogen and creatinine, and only occasional, mild hypercalcemia. The magnitude of the increased renal uptake of MDP observed could not be explained by alterations in iron metabolism or by dehydration. Drug-induced renal retention of MDP by a factor of 2 or more above normal appears to be a useful indicator of tubular damage when other parameters of renal function are sometimes normal.« less

Untethered Recyclable Tubular Actuators with Versatile Locomotion for Soft Continuum Robots.

PubMed

Qian, Xiaojie; Chen, Qiaomei; Yang, Yang; Xu, Yanshuang; Li, Zhen; Wang, Zhenhua; Wu, Yahe; Wei, Yen; Ji, Yan

2018-05-27

Stimuli-responsive materials offer a distinguished platform to build tether-free compact soft robots, which can combine sensing and actuation without a linked power supply. In the past, tubular soft robots have to be made by multiple components with various internal channels or complex cavities assembled together. Moreover, robust processing, complex locomotion, simple structure, and easy recyclability represent major challenges in this area. Here, it is shown that those challenges can be tackled by liquid crystalline elastomers with allyl sulfide functional groups. The light-controlled exchange reaction between allyl sulfide groups allows flexible processing of tubular soft robots/actuators, which does not need any assisting materials. Complex locomotion demonstrated here includes reversible simultaneous bending and elongation; reversible diameter expansion; and omnidirectional bending via remote infrared light control. Different modes of actuation can be programmed into the same tube without the routine assembly of multiple tubes as used in the past. In addition, the exchange reaction also makes it possible to use the same single tube repeatedly to perform different functions by erasing and reprogramming. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced Flexible Tubular Microelectrode with Conducting Polymer for Multi-Functional Implantable Tissue-Machine Interface.

PubMed

Tian, Hong-Chang; Liu, Jing-Quan; Kang, Xiao-Yang; Tang, Long-Jun; Wang, Ming-Hao; Ji, Bo-Wen; Yang, Bin; Wang, Xiao-Lin; Chen, Xiang; Yang, Chun-Sheng

2016-05-27

Implantable biomedical microdevices enable the restoration of body function and improvement of health condition. As the interface between artificial machines and natural tissue, various kinds of microelectrodes with high density and tiny size were developed to undertake precise and complex medical tasks through electrical stimulation and electrophysiological recording. However, if only the electrical interaction existed between electrodes and muscle or nerve tissue without nutrition factor delivery, it would eventually lead to a significant symptom of denervation-induced skeletal muscle atrophy. In this paper, we developed a novel flexible tubular microelectrode integrated with fluidic drug delivery channel for dynamic tissue implant. First, the whole microelectrode was made of biocompatible polymers, which could avoid the drawbacks of the stiff microelectrodes that are easy to be broken and damage tissue. Moreover, the microelectrode sites were circumferentially distributed on the surface of polymer microtube in three dimensions, which would be beneficial to the spatial selectivity. Finally, the in vivo results confirmed that our implantable tubular microelectrodes were suitable for dynamic electrophysiological recording and simultaneous fluidic drug delivery, and the electrode performance was further enhanced by the conducting polymer modification.

Self-assembly of multi-stranded RNA motifs into lattices and tubular structures

DOE PAGES

Stewart, Jaimie Marie; Subramanian, Hari K. K.; Franco, Elisa

2017-02-16

Rational design of nucleic acidmolecules yields selfassembling scaffolds with increasing complexity, size and functionality. It is an open question whether design methods tailored to build DNA nanostructures can be adapted to build RNA nanostructures with comparable features. We demonstrate the formation of RNA lattices and tubular assemblies from double crossover (DX) tiles, a canonical motif in DNA nanotechnology. Tubular structures can exceed 1 m in length, suggesting that this DX motif can produce very robust lattices. Some of these tubes spontaneously form with left-handed chirality. We obtain assemblies by using two methods: a protocol where gel-extracted RNA strands are slowlymore » annealed, and a one-pot transcription and anneal procedure. We then identify the tile nick position as a structural requirement for lattice formation. These results demonstrate that stable RNA structures can be obtained with design tools imported from DNA nanotechnology. These large assemblies could be potentially integrated with a variety of functional RNA motifs for drug or nanoparticle delivery, or for colocalization of cellular components.« less

Self-assembly of multi-stranded RNA motifs into lattices and tubular structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stewart, Jaimie Marie; Subramanian, Hari K. K.; Franco, Elisa

Rational design of nucleic acidmolecules yields selfassembling scaffolds with increasing complexity, size and functionality. It is an open question whether design methods tailored to build DNA nanostructures can be adapted to build RNA nanostructures with comparable features. We demonstrate the formation of RNA lattices and tubular assemblies from double crossover (DX) tiles, a canonical motif in DNA nanotechnology. Tubular structures can exceed 1 m in length, suggesting that this DX motif can produce very robust lattices. Some of these tubes spontaneously form with left-handed chirality. We obtain assemblies by using two methods: a protocol where gel-extracted RNA strands are slowlymore » annealed, and a one-pot transcription and anneal procedure. We then identify the tile nick position as a structural requirement for lattice formation. These results demonstrate that stable RNA structures can be obtained with design tools imported from DNA nanotechnology. These large assemblies could be potentially integrated with a variety of functional RNA motifs for drug or nanoparticle delivery, or for colocalization of cellular components.« less

Recovery of Na-glucose cotransport activity after renal ischemia is impaired in mice lacking vimentin.

PubMed

Runembert, Isabelle; Couette, Sylviane; Federici, Pierre; Colucci-Guyon, Emma; Babinet, Charles; Briand, Pascale; Friedlander, Gérard; Terzi, Fabiola

2004-11-01

Vimentin, an intermediate filament protein mainly expressed in mesenchyma-derived cells, is reexpressed in renal tubular epithelial cells under many pathological conditions, characterized by intense cell proliferation. Whether vimentin reexpression is only a marker of cell dedifferentiation or is instrumental in the maintenance of cell structure and/or function is still unknown. Here, we used vimentin knockout mice (Vim(-/-)) and an experimental model of acute renal injury (30-min bilateral renal ischemia) to explore the role of vimentin. Bilateral renal ischemia induced an initial phase of acute tubular necrosis that did not require vimentin and was similar, in terms of morphological and functional changes, in Vim(+/+) and Vim(-/-) mice. However, vimentin was essential to favor Na-glucose cotransporter 1 localization to brush-border membranes and to restore Na-glucose cotransport activity in regenerating tubular cells. We show that the effect of vimentin inactivation is specific and results in persistent glucosuria. We propose that vimentin is part of a structural network that favors carrier localization to plasma membranes to restore transport activity in injured kidneys.

Self-assembly of multi-stranded RNA motifs into lattices and tubular structures

PubMed Central

Stewart, Jaimie Marie; Subramanian, Hari K. K.

2017-01-01

Abstract Rational design of nucleic acid molecules yields self-assembling scaffolds with increasing complexity, size and functionality. It is an open question whether design methods tailored to build DNA nanostructures can be adapted to build RNA nanostructures with comparable features. Here we demonstrate the formation of RNA lattices and tubular assemblies from double crossover (DX) tiles, a canonical motif in DNA nanotechnology. Tubular structures can exceed 1 μm in length, suggesting that this DX motif can produce very robust lattices. Some of these tubes spontaneously form with left-handed chirality. We obtain assemblies by using two methods: a protocol where gel-extracted RNA strands are slowly annealed, and a one-pot transcription and anneal procedure. We identify the tile nick position as a structural requirement for lattice formation. Our results demonstrate that stable RNA structures can be obtained with design tools imported from DNA nanotechnology. These large assemblies could be potentially integrated with a variety of functional RNA motifs for drug or nanoparticle delivery, or for colocalization of cellular components. PMID:28204562

Cellular Responses to Mechanical Stress Selected Contribution: A Three-Dimensional Model for Assessment of in Vitro Toxicity in Balaena Mysticetus Renal Tissue

NASA Technical Reports Server (NTRS)

Goodwin, T. J.; Coate-Li, L.; Linnehan, R. M.; Hammond, T. G.

2000-01-01

This study established two- and three-dimensional renal proximal tubular cell cultures of the endangered species bowhead whale (Balaena mysticetus), developed SV40-transfected cultures, and cloned the 61-amino acid open reading frame for the metallothionein protein, the primary binding site for heavy metal contamination in mammals. Microgravity research, modulations in mechanical culture conditions (modeled microgravity), and shear stress have spawned innovative approaches to understanding the dynamics of cellular interactions, gene expression, and differentiation in several cellular systems. These investigations have led to the creation of ex vivo tissue models capable of serving as physiological research analogs for three-dimensional cellular interactions. These models are enabling studies in immune function, tissue modeling for basic research, and neoplasia. Three-dimensional cellular models emulate aspects of in vivo cellular architecture and physiology and may facilitate environmental toxicological studies aimed at elucidating biological functions and responses at the cellular level. Marine mammals occupy a significant ecological niche (72% of the Earth's surface is water) in terms of the potential for information on bioaccumulation and transport of terrestrial and marine environmental toxins in high-order vertebrates. Few ex vivo models of marine mammal physiology exist in vitro to accomplish the aforementioned studies. Techniques developed in this investigation, based on previous tissue modeling successes, may serve to facilitate similar research in other marine mammals.

Selected contribution: a three-dimensional model for assessment of in vitro toxicity in balaena mysticetus renal tissue

NASA Technical Reports Server (NTRS)

Goodwin, T. J.; Coate-Li, L.; Linnehan, R. M.; Hammond, T. G.

2000-01-01

This study established two- and three-dimensional renal proximal tubular cell cultures of the endangered species bowhead whale (Balaena mysticetus), developed SV40-transfected cultures, and cloned the 61-amino acid open reading frame for the metallothionein protein, the primary binding site for heavy metal contamination in mammals. Microgravity research, modulations in mechanical culture conditions (modeled microgravity), and shear stress have spawned innovative approaches to understanding the dynamics of cellular interactions, gene expression, and differentiation in several cellular systems. These investigations have led to the creation of ex vivo tissue models capable of serving as physiological research analogs for three-dimensional cellular interactions. These models are enabling studies in immune function, tissue modeling for basic research, and neoplasia. Three-dimensional cellular models emulate aspects of in vivo cellular architecture and physiology and may facilitate environmental toxicological studies aimed at elucidating biological functions and responses at the cellular level. Marine mammals occupy a significant ecological niche (72% of the Earth's surface is water) in terms of the potential for information on bioaccumulation and transport of terrestrial and marine environmental toxins in high-order vertebrates. Few ex vivo models of marine mammal physiology exist in vitro to accomplish the aforementioned studies. Techniques developed in this investigation, based on previous tissue modeling successes, may serve to facilitate similar research in other marine mammals.

Effect of nephrotoxic treatment with gentamicin on rats chronically exposed to uranium.

PubMed

Rouas, Caroline; Stefani, Johanna; Grison, Stéphane; Grandcolas, Line; Baudelin, Cédric; Dublineau, Isabelle; Pallardy, Marc; Gueguen, Yann

2011-01-11

Uranium is a radioactive heavy metal with a predominantly chemical toxicity, affecting especially the kidneys and more particularly the proximal tubular structure. Until now, few experimental studies have examined the effect of chronic low-dose exposure to uranium on kidney integrity: these mainly analyse standard markers such as creatinine and urea, and none has studied the effect of additional co-exposure to a nephrotoxic agent on rats chronically exposed to uranium. The aim of the present study is to examine the potential cumulative effect of treating uranium-exposed rats with a nephrotoxic drug. Neither physiological indicators (diuresis and creatinine clearance) nor standard plasma and urine markers (creatinine, urea and total protein) levels were deteriorated when uranium exposure was combined with gentamicin-induced nephrotoxicity. A histological study confirmed the preferential impact of gentamicin on the tubular structure and showed that uranium did not aggravate the histopathological renal lesions. Finally, the use of novel markers of kidney toxicity, such as KIM-1, osteopontin and kallikrein, provides new knowledge about the nephrotoxicity threshold of gentamicin, and allows us to conclude that under our experimental conditions, low dose uranium exposure did not induce signs of nephrotoxicity or enhance renal sensitivity to another nephrotoxicant. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Idiopathic hypercalciuria with bilateral macular colobomata: a new variant of oculo-renal syndrome.

PubMed

Meier, W; Blumberg, A; Imahorn, W; De Luca, F; Wildberger, H; Oetliker, O

1979-01-01

Two siblings from a consanguineous family, suffering from nephrocalcinosis and nephrolithiasis caused by idiopathic hypercalciuria are described. The condition is associated with bilateral macular colobomata and tapeto-retinal degeneration. It is known that the latter can occur together with different nephropathies; however, until now it has never been described in combination with idiopathic hypercalciuria. Blood calcium levels were found to be normal, calcium excretion rates were, with one exception, more than 6 mg/kg/24 h corrected for 100 ml GFR. Hypomagnesemia of 1.5 and 1.2 mg/dl and hyermagnesuria of 1.9 and 2.5 mg/kg/24 h corrected for 100 ml GFR were found in both patients. Tubular phosphate reabsorption reached 87% and 84% at serum parathormone levels of 0.34 microgram/l and 0.31 microgram/l in the two patients, respectively. Under calcium and magnesium loading the clearance rates of calcium and magnesium were raised whilst there was only a small insignificant increase in the blood levels of these cations. Acid-base titrations showed normal excretion rates of acid and base in one patient and a mild proximal tubular acidosis in the other. Quantitative investigation of the renal concentrating and diluting capacity established a decrease in the formation of the medullary concentrating gradient in both patients.

Genetic heterogeneity in familial renal magnesium wasting.

PubMed

Kantorovich, Vitaly; Adams, John S; Gaines, Jade E; Guo, Xiuqing; Pandian, Murugan R; Cohn, Daniel H; Rude, Robert K

2002-02-01

Isolated hereditary renal magnesium (Mg) wasting may result from mutations in the renal tubular epithelial cell tight junction protein paracellin-1 gene or the tubular Na(+),K(+)-ATPase gamma-subunit gene FXYD2. The FXYD2 gene mutation was discovered in two Dutch families as an autosomal dominant disorder. It is characterized by isolated renal Mg wasting with resultant symptomatic hypomagnesemia. The defective FXYD2 gene in these families mapped to chromosome 11q23. Here, we describe an American family with a similar phenotype but without linkage to the 11q23 locus; in testing 22 individuals in the pedigree multipoint LOD scores for five different loci from the 11q23 region were equal to -2.97. Compared with unaffected family members and normal controls, affected family members harbored significant reductions in the serum and lymphocyte Mg concentrations and in the serum immunoreactive PTH level with a 4-fold increase in the mean fractional urinary Mg excretion rate during a normomagnesemic clamp. Bone mineral density at the lumbar spine and proximal femur was significantly reduced in affected family members. In conclusion, our data demonstrate locus heterogeneity for the phenotype of isolated renal Mg wasting with hypomagnesemia and suggest that hypomagnesemia, at least in this pedigree, may be associated with low bone mass.