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Sedaka R, Huang J, Yamaguchi S, Lovelady C, Hsu JS, Shinde S, Kasztan M, Crossman DK, Saigusa T. Accelerated cystogenesis by dietary protein load is dependent on, but not initiated by kidney macrophages. Front Med (Lausanne) 2023; 10:1173674. [PMID: 37538309 PMCID: PMC10394241 DOI: 10.3389/fmed.2023.1173674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 07/03/2023] [Indexed: 08/05/2023] Open
Abstract
Background Disease severity of autosomal dominant polycystic kidney disease (ADPKD) is influenced by diet. Dietary protein, a recognized cyst-accelerating factor, is catabolized into amino acids (AA) and delivered to the kidney leading to renal hypertrophy. Injury-induced hypertrophic signaling in ADPKD results in increased macrophage (MФ) activation and inflammation followed by cyst growth. We hypothesize that the cystogenesis-prompting effects of HP diet are caused by increased delivery of specific AA to the kidney, ultimately stimulating MФs to promote cyst progression. Methods Pkd1flox/flox mice with and without Cre (CAGG-ER) were given tamoxifen to induce global gene deletion (Pkd1KO). Pkd1KO mice were fed either a low (LP; 6%), normal (NP; 18%), or high (HP; 60%) protein diet for 1 week (early) or 6 weeks (chronic). Mice were then euthanized and tissues were used for histology, immunofluorescence and various biochemical assays. One week fed kidney tissue was cell sorted to isolate tubular epithelial cells for RNA sequencing. Results Chronic dietary protein load in Pkd1KO mice increased kidney weight, number of kidney infiltrating and resident MФs, chemokines, cytokines and cystic index compared to LP diet fed mice. Accelerated cyst growth induced by chronic HP were attenuated by liposomal clodronate-mediated MФ depletion. Early HP diet fed Pkd1KO mice had larger cystic kidneys compared to NP or LP fed counterparts, but without increases in the number of kidney MФs, cytokines, or markers of tubular injury. RNA sequencing of tubular epithelial cells in HP compared to NP or LP diet group revealed increased expression of sodium-glutamine transporter Snat3, chloride channel Clcnka, and gluconeogenesis marker Pepck1, accompanied by increased excretion of urinary ammonia, a byproduct of glutamine. Early glutamine supplementation in Pkd1KO mice lead to kidney hypertrophy. Conclusion Chronic dietary protein load-induced renal hypertrophy and accelerated cyst growth in Pkd1KO mice is dependent on both infiltrating and resident MФ recruitment and subsequent inflammatory response. Early cyst expansion by HP diet, however, is relient on increased delivery of glutamine to kidney epithelial cells, driving downstream metabolic changes prior to inflammatory provocation.
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Affiliation(s)
- Randee Sedaka
- Section of Cardio-Renal Physiology and Medicine, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Jifeng Huang
- Section of Cardio-Renal Physiology and Medicine, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Shinobu Yamaguchi
- Section of Cardio-Renal Physiology and Medicine, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Caleb Lovelady
- Section of Cardio-Renal Physiology and Medicine, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Jung-Shan Hsu
- Section of Cardio-Renal Physiology and Medicine, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Sejal Shinde
- Section of Cardio-Renal Physiology and Medicine, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Malgorzata Kasztan
- Division of Pediatric Hematology/Oncology, Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, United States
| | - David K. Crossman
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Takamitsu Saigusa
- Section of Cardio-Renal Physiology and Medicine, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
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Wild J, Jung R, Knopp T, Efentakis P, Benaki D, Grill A, Wegner J, Molitor M, Garlapati V, Rakova N, Markó L, Marton A, Mikros E, Münzel T, Kossmann S, Rauh M, Nakano D, Kitada K, Luft F, Waisman A, Wenzel P, Titze J, Karbach S. Aestivation motifs explain hypertension and muscle mass loss in mice with psoriatic skin barrier defect. Acta Physiol (Oxf) 2021; 232:e13628. [PMID: 33590724 DOI: 10.1111/apha.13628] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Revised: 02/11/2021] [Accepted: 02/11/2021] [Indexed: 12/12/2022]
Abstract
AIM Recent evidence suggests that arterial hypertension could be alternatively explained as a physiological adaptation response to water shortage, termed aestivation, which relies on complex multi-organ metabolic adjustments to prevent dehydration. Here, we tested the hypothesis that chronic water loss across diseased skin leads to similar adaptive water conservation responses as observed in experimental renal failure or high salt diet. METHODS We studied mice with keratinocyte-specific overexpression of IL-17A which develop severe psoriasis-like skin disease. We measured transepidermal water loss and solute and water excretion in the urine. We quantified glomerular filtration rate (GFR) by intravital microscopy, and energy and nitrogen pathways by metabolomics. We measured skin blood flow and transepidermal water loss (TEWL) in conjunction with renal resistive indices and arterial blood pressure. RESULTS Psoriatic animals lost large amounts of water across their defective cutaneous epithelial barrier. Metabolic adaptive water conservation included mobilization of nitrogen and energy from muscle to increase organic osmolyte production, solute-driven maximal anti-diuresis at normal GFR, increased metanephrine and angiotensin 2 levels, and cutaneous vasoconstriction to limit TEWL. Heat exposure led to cutaneous vasodilation and blood pressure normalization without parallel changes in renal resistive index, albeit at the expense of further increased TEWL. CONCLUSION Severe cutaneous water loss predisposes psoriatic mice to lethal dehydration. In response to this dehydration stress, the mice activate aestivation-like water conservation motifs to maintain their body hydration status. The circulatory water conservation response explains their arterial hypertension. The nitrogen-dependency of the metabolic water conservation response explains their catabolic muscle wasting.
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Affiliation(s)
- Johannes Wild
- Center for Thrombosis and Hemostasis (CTH) Johannes Gutenberg‐University Mainz Mainz Germany
- Center for Cardiology Cardiology IJohannes Gutenberg‐University Mainz Mainz Germany
| | - Rebecca Jung
- Center for Thrombosis and Hemostasis (CTH) Johannes Gutenberg‐University Mainz Mainz Germany
| | - Tanja Knopp
- Center for Thrombosis and Hemostasis (CTH) Johannes Gutenberg‐University Mainz Mainz Germany
| | - Panagiotis Efentakis
- Center for Thrombosis and Hemostasis (CTH) Johannes Gutenberg‐University Mainz Mainz Germany
- Faculty of Pharmacy University of AthensPanepistimiopolis of Zographou Athens Greece
| | - Dimitra Benaki
- Faculty of Pharmacy University of AthensPanepistimiopolis of Zographou Athens Greece
| | - Alexandra Grill
- Center for Thrombosis and Hemostasis (CTH) Johannes Gutenberg‐University Mainz Mainz Germany
| | - Joanna Wegner
- Department of Dermatology Johannes Gutenberg‐University Mainz Mainz Germany
| | - Michael Molitor
- Center for Thrombosis and Hemostasis (CTH) Johannes Gutenberg‐University Mainz Mainz Germany
- Center for Cardiology Cardiology IJohannes Gutenberg‐University Mainz Mainz Germany
| | - Venkata Garlapati
- Center for Thrombosis and Hemostasis (CTH) Johannes Gutenberg‐University Mainz Mainz Germany
| | - Natalia Rakova
- Division of Nephrology and Hypertension University Clinic Erlangen Erlangen Germany
| | - Lajos Markó
- Experimental and Clinical Research CenterMax Delbrück Center for Molecular Medicine Berlin Germany
| | - Adriana Marton
- Programme in Cardiovascular and Metabolic DisordersDuke‐NUS Medical School Singapore Singapore
| | - Emmanuel Mikros
- Faculty of Pharmacy University of AthensPanepistimiopolis of Zographou Athens Greece
| | - Thomas Münzel
- Center for Cardiology Cardiology IJohannes Gutenberg‐University Mainz Mainz Germany
| | | | - Manfred Rauh
- Research Laboratory Division of Paediatrics University Clinic Erlangen Erlangen Germany
| | - Daisuke Nakano
- Department of Pharmacology Faculty of Medicine Kagawa University Miki‐cho Kagawa Japan
| | - Kento Kitada
- Programme in Cardiovascular and Metabolic DisordersDuke‐NUS Medical School Singapore Singapore
- Department of Pharmacology Faculty of Medicine Kagawa University Miki‐cho Kagawa Japan
| | - Friedrich Luft
- Experimental and Clinical Research CenterMax Delbrück Center for Molecular Medicine Berlin Germany
| | - Ari Waisman
- Institute for Molecular Medicine University Medical Center of Mainz Mainz Germany
| | - Philip Wenzel
- Center for Thrombosis and Hemostasis (CTH) Johannes Gutenberg‐University Mainz Mainz Germany
- Center for Cardiology Cardiology IJohannes Gutenberg‐University Mainz Mainz Germany
| | - Jens Titze
- Division of Nephrology and Hypertension University Clinic Erlangen Erlangen Germany
- Programme in Cardiovascular and Metabolic DisordersDuke‐NUS Medical School Singapore Singapore
- Division of Nephrology Duke University School of Medicine Durham NC USA
| | - Susanne Karbach
- Center for Thrombosis and Hemostasis (CTH) Johannes Gutenberg‐University Mainz Mainz Germany
- Center for Cardiology Cardiology IJohannes Gutenberg‐University Mainz Mainz Germany
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Marton A, Kaneko T, Kovalik JP, Yasui A, Nishiyama A, Kitada K, Titze J. Organ protection by SGLT2 inhibitors: role of metabolic energy and water conservation. Nat Rev Nephrol 2020; 17:65-77. [PMID: 33005037 DOI: 10.1038/s41581-020-00350-x] [Citation(s) in RCA: 77] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/18/2020] [Indexed: 12/17/2022]
Abstract
Therapeutic inhibition of the sodium-glucose co-transporter 2 (SGLT2) leads to substantial loss of energy (in the form of glucose) and additional solutes (in the form of Na+ and its accompanying anions) in urine. However, despite the continuously elevated solute excretion, long-term osmotic diuresis does not occur in humans with SGLT2 inhibition. Rather, patients on SGLT2 inhibitor therapy adjust to the reduction in energy availability and conserve water. The metabolic adaptations that are induced by SGLT2 inhibition are similar to those observed in aestivation - an evolutionarily conserved survival strategy that enables physiological adaptation to energy and water shortage. Aestivators exploit amino acids from muscle to produce glucose and fatty acid fuels. This endogenous energy supply chain is coupled with nitrogen transfer for organic osmolyte production, which allows parallel water conservation. Moreover, this process is often accompanied by a reduction in metabolic rate. By comparing aestivation metabolism with the fuel switches that occur during therapeutic SGLT2 inhibition, we suggest that SGLT2 inhibitors induce aestivation-like metabolic patterns, which may contribute to the improvements in cardiac and renal function observed with this class of therapeutics.
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Affiliation(s)
- Adriana Marton
- Programme in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Tatsuroh Kaneko
- Medicine Division, Nippon Boehringer Ingelheim Co., Ltd, Tokyo, Japan
| | - Jean-Paul Kovalik
- Programme in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Atsutaka Yasui
- Medicine Division, Nippon Boehringer Ingelheim Co., Ltd, Tokyo, Japan
| | - Akira Nishiyama
- Department of Pharmacology, Faculty of Medicine, Kagawa University, Kagawa, Japan
| | - Kento Kitada
- Programme in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore.,Department of Pharmacology, Faculty of Medicine, Kagawa University, Kagawa, Japan
| | - Jens Titze
- Programme in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore. .,Division of Nephrology and Hypertension, University Clinic Erlangen, Erlangen, Germany. .,Division of Nephrology, Duke University Medical Center, Durham, NC, USA.
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Kitada K, Daub S, Zhang Y, Klein JD, Nakano D, Pedchenko T, Lantier L, LaRocque LM, Marton A, Neubert P, Schröder A, Rakova N, Jantsch J, Dikalova AE, Dikalov SI, Harrison DG, Müller DN, Nishiyama A, Rauh M, Harris RC, Luft FC, Wassermann DH, Sands JM, Titze J. High salt intake reprioritizes osmolyte and energy metabolism for body fluid conservation. J Clin Invest 2017; 127:1944-1959. [PMID: 28414295 DOI: 10.1172/jci88532] [Citation(s) in RCA: 143] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 02/17/2017] [Indexed: 12/25/2022] Open
Abstract
Natriuretic regulation of extracellular fluid volume homeostasis includes suppression of the renin-angiotensin-aldosterone system, pressure natriuresis, and reduced renal nerve activity, actions that concomitantly increase urinary Na+ excretion and lead to increased urine volume. The resulting natriuresis-driven diuretic water loss is assumed to control the extracellular volume. Here, we have demonstrated that urine concentration, and therefore regulation of water conservation, is an important control system for urine formation and extracellular volume homeostasis in mice and humans across various levels of salt intake. We observed that the renal concentration mechanism couples natriuresis with correspondent renal water reabsorption, limits natriuretic osmotic diuresis, and results in concurrent extracellular volume conservation and concentration of salt excreted into urine. This water-conserving mechanism of dietary salt excretion relies on urea transporter-driven urea recycling by the kidneys and on urea production by liver and skeletal muscle. The energy-intense nature of hepatic and extrahepatic urea osmolyte production for renal water conservation requires reprioritization of energy and substrate metabolism in liver and skeletal muscle, resulting in hepatic ketogenesis and glucocorticoid-driven muscle catabolism, which are prevented by increasing food intake. This natriuretic-ureotelic, water-conserving principle relies on metabolism-driven extracellular volume control and is regulated by concerted liver, muscle, and renal actions.
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Kim YM, Kim WY, Nam SA, Choi AR, Kim H, Kim YK, Kim HS, Kim J. Role of Prox1 in the Transforming Ascending Thin Limb of Henle's Loop during Mouse Kidney Development. PLoS One 2015; 10:e0127429. [PMID: 25993027 PMCID: PMC4438060 DOI: 10.1371/journal.pone.0127429] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 04/15/2015] [Indexed: 02/04/2023] Open
Abstract
The homeobox transcription factor Prox1 is critical to the development of many embryonic organs and tissues, although current understanding of its expression in the developing renal medulla is limited. We examined the functional role of Prox1 during mouse kidney development with particular emphasis on the developing loop of Henle. Our data show that Prox1 is expressed in the transdifferentiating region from the NKCC2-positive thick ascending limb, into the CLC-K1-positive ascending thin limb of Henle’s loop beginning at embryonic day 18. From 1 to 14 days of age, Prox1-positive cells gradually disappeared from the papillary tip, and remained in the initial part of inner medulla after 21 days. In this transforming area, no Prox1 was observed in cells undergoing apoptosis but was expressed strongly in the remaining cells, which differentiated into ascending thin limb epithelial cells. In vitro and in vivo approaches showed that Prox1 expression increases where the osmolality is near optimal range, but decreases at below- or above-optimal ranges. Renal hypoosmolality induced by furosemide (NKCC2 inhibitor) inhibited Prox1 expression and delayed maturation of the ascending limb of Henle’s loop. Together, these studies suggest that Prox1 appears to be a critical stage specific regulator of specifying ascending thin limb cell fate and that its expression is regulated by osmolality.
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Affiliation(s)
- Yu-mi Kim
- Department of Anatomy and Cell Death Disease Research Center, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Wan-Young Kim
- Department of Anatomy and Cell Death Disease Research Center, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Sun Ah Nam
- Department of Anatomy and Cell Death Disease Research Center, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - A-Rum Choi
- Department of Anatomy and Cell Death Disease Research Center, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Hyang Kim
- Division of Nephrology, Kangbuk Samsung Hospital, Sungkyunkwan University, School of Medicine, Seoul, Korea
| | - Yong-Kyun Kim
- Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Hak-Soo Kim
- Department of Anatomy and Cell Death Disease Research Center, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Jin Kim
- Department of Anatomy and Cell Death Disease Research Center, College of Medicine, The Catholic University of Korea, Seoul, Korea
- * E-mail:
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Abstract
UT-A and UT-B families of urea transporters consist of multiple isoforms that are subject to regulation of both acutely and by long-term measures. This chapter provides a brief overview of the expression of the urea transporter forms and their locations in the kidney. Rapid regulation of UT-A1 results from the combination of phosphorylation and membrane accumulation. Phosphorylation of UT-A1 has been linked to vasopressin and hyperosmolality, although through different kinases. Other acute influences on urea transporter activity are ubiquitination and glycosylation, both of which influence the membrane association of the urea transporter, again through different mechanisms. Long-term regulation of urea transport is most closely associated with the environment that the kidney experiences. Low-protein diets may influence the amount of urea transporter available. Conditions of osmotic diuresis, where urea concentrations are low, will prompt an increase in urea transporter abundance. Although adrenal steroids affect urea transporter abundance, conflicting reports make conclusions tenuous. Urea transporters are upregulated when P2Y2 purinergic receptors are decreased, suggesting a role for these receptors in UT regulation. Hypercalcemia and hypokalemia both cause urine concentration deficiencies. Urea transporter abundances are reduced in aging animals and animals with angiotensin-converting enzyme deficiencies. This chapter will provide information about both rapid and long-term regulation of urea transporters and provide an introduction into the literature.
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Affiliation(s)
- Janet D Klein
- Renal Division, Department of Medicine and Department of Physiology, Emory University School of Medicine, WMB Room 3319B, 1639 Pierce Drive, NE, Atlanta, GA, 30322, USA,
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Bou Matar RN, Malik B, Wang XH, Martin CF, Eaton DC, Sands JM, Klein JD. Protein abundance of urea transporters and aquaporin 2 change differently in nephrotic pair-fed vs. non-pair-fed rats. Am J Physiol Renal Physiol 2012; 302:F1545-53. [PMID: 22461302 PMCID: PMC3378098 DOI: 10.1152/ajprenal.00686.2011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 03/20/2012] [Indexed: 11/22/2022] Open
Abstract
Salt and water retention is a hallmark of nephrotic syndrome (NS). In this study, we test for changes in the abundance of urea transporters, aquaporin 2 (AQP2), Na-K-2Cl cotransporter 2 (NKCC2), and Na-Cl cotransporter (NCC), in non-pair-fed and pair-fed nephrotic animals. Doxorubicin-injected male Sprague-Dawley rats (n = 10) were followed in metabolism cages. Urinary excretion of protein, sodium, and urea was measured periodically. Kidney inner medulla (IM), outer medulla, and cortex tissue samples were dissected and analyzed for mRNA and protein abundances. At 3 wk, all doxorubicin-treated rats developed features of NS, with a ninefold increase in urine protein excretion (from 144 ± 21 to 1,107 ± 165 mg/day; P < 0.001) and reduced urinary sodium excretion (from 0.17 to 0.12 meq/day; P < 0.001). Urine osmolalities were reduced in the nephrotic animals (1,057 ± 37, treatment vs. 1,754 ± 131, control). Unlike animals fed ad libitum, UT-A1 protein abundance was unchanged in nephrotic pair-fed rats. Glycosylated AQP2 was reduced in the IM base of both nephrotic groups. Abundances of NKCC2 and NCC were consistently reduced (71 ± 7 and 33 ± 13%, respectively) in both nephrotic pair-fed animals and animals fed ad libitum. In pair-fed nephrotic rats, we observed an increase in the cleaved form of membrane-bound γ-epithelial sodium channel (ENaC). However, α- and β-ENaC subunits were unaltered. NKCC2 and AQP2 mRNA levels were similar in treated vs. control rats. We conclude that dietary protein intake affects the response of medullary transport proteins to NS.
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Affiliation(s)
- Raed N Bou Matar
- Department of Pediatric Medicine, Emory University, Atlanta, Georgia 30322, USA
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Ilori TO, Wang Y, Blount MA, Martin CF, Sands JM, Klein JD. Acute calcineurin inhibition with tacrolimus increases phosphorylated UT-A1. Am J Physiol Renal Physiol 2012; 302:F998-F1004. [PMID: 22205230 PMCID: PMC3395357 DOI: 10.1152/ajprenal.00358.2011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 12/21/2011] [Indexed: 11/22/2022] Open
Abstract
UT-A1, the urea transporter present in the apical membrane of the inner medullary collecting duct, is crucial to the kidney's ability to concentrate urine. Phosphorylation of UT-A1 on serines 486 and 499 is important for plasma membrane trafficking. The effect of calcineurin on dephosphorylation of UT-A1 was investigated. Inner medullary collecting ducts from Sprague-Dawley rats were metabolically labeled and treated with tacrolimus to inhibit calcineurin or calyculin to inhibit protein phosphatases 1 and 2A. UT-A1 was immunoprecipitated, electrophoresed, blotted, and total UT-A1 phosphorylation was assessed by autoradiography. Total UT-A1 was determined by Western blotting. A phospho-specific antibody to pser486-UT-A1 was used to determine whether serine 486 can be hyperphosphorylated by inhibiting phosphatases. Inhibition of calcineurin showed an increase in phosphorylation per unit protein at serine 486. In contrast, inhibition of phosphatases 1 and 2A resulted in an increase in UT-A1 phosphorylation but no increase in pser486-UT-A1. In vitro perfusion of inner medullary collecting ducts showed tacrolimus-stimulated urea permeability consistent with stimulated urea transport. The location of phosphorylated UT-A1 in rats treated acutely and chronically with tacrolimus was determined using immunohistochemistry. Inner medullary collecting ducts of the acutely treated rats showed increased apical membrane association of phosphorylated UT-A1 while chronic treatment reduced membrane association of phosphorylated UT-A1. We conclude that UT-A1 may be dephosphorylated by multiple phosphatases and that the PKA-phosphorylated serine 486 is dephosphorylated by calcineurin. This is the first documentation of the role of phosphatases and the specific site of phosphorylation of UT-A1, in response to tacrolimus.
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Affiliation(s)
- Titilayo O Ilori
- Renal Division, Dept. of Medicine, Emory University, 1639 Pierce Dr., Atlanta, GA 30322, USA.
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Jin W, Yao X, Wang T, Ji Q, Li Y, Yang X, Yao L. Effects of hyperosmolality on expression of urea transporter A2 and aquaporin 2 in mouse medullary collecting duct cells. JOURNAL OF HUAZHONG UNIVERSITY OF SCIENCE AND TECHNOLOGY. MEDICAL SCIENCES = HUA ZHONG KE JI DA XUE XUE BAO. YI XUE YING DE WEN BAN = HUAZHONG KEJI DAXUE XUEBAO. YIXUE YINGDEWEN BAN 2012; 32:59-64. [PMID: 22282246 DOI: 10.1007/s11596-012-0010-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Indexed: 12/25/2022]
Abstract
In this study, the effects of hyperosmolality on the expression of urea transporter A2 (UTA2) and aquaporin 2 (AQP2) were investigated in transfected immortalized mouse medullary collecting duct (mIMCD3) cell line. AQP2-GFP-pCMV6 and UTA2-GFP-pCMV6 plasmids were stably transfected into mIMCD3 cells respectively. Transfected mIMCD3 and control cells were cultured in different hypertonic media, which were made by NaCl alone, urea alone, or an equiosmolar mixture of NaCl and urea. The mRNA and protein expression of AQP2 was elevated by the stimulation of NaCl alone, urea alone and NaCl plus urea in AQP2-mIMCD3 cells; whereas NaCl alone and NaCl plus urea rather than urea alone increased the mRNA and protein expression of UTA2 in UTA2-mIMCD3 cells, and all the expression presented an osmolality-dependent manner. Moreover, the mRNA and protein expression of UTA2 rather than AQP2 was found to be synergistically up-regulated by a combination of NaCl and urea in mIMCD3 cells. It is concluded that NaCl and urea synergistically induce the expression of UTA2 rather than AQP2 in mIMCD3 cells, and hyperosmolality probably mediates the expression of AQP2 and UTA2 through different mechanisms.
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Affiliation(s)
- Wenmin Jin
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Xi Yao
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Taoxia Wang
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Qianqian Ji
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Yongxia Li
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Xiao Yang
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Lijun Yao
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China.
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Liantonio A, Gramegna G, Camerino GM, Dinardo MM, Scaramuzzi A, Potenza MA, Montagnani M, Procino G, Lasorsa DR, Mastrofrancesco L, Laghezza A, Fracchiolla G, Loiodice F, Perrone MG, Lopedota A, Conte S, Penza R, Valenti G, Svelto M, Camerino DC. In-vivo administration of CLC-K kidney chloride channels inhibitors increases water diuresis in rats. J Hypertens 2012; 30:153-67. [DOI: 10.1097/hjh.0b013e32834d9eb9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Abstract
Urea transport proteins were initially proposed to exist in the kidney in the late 1980s when studies of urea permeability revealed values in excess of those predicted by simple lipid-phase diffusion and paracellular transport. Less than a decade later, the first urea transporter was cloned. Currently, the SLC14A family of urea transporters contains two major subgroups: SLC14A1, the UT-B urea transporter originally isolated from erythrocytes; and SLC14A2, the UT-A group with six distinct isoforms described to date. In the kidney, UT-A1 and UT-A3 are found in the inner medullary collecting duct; UT-A2 is located in the thin descending limb, and UT-B is located primarily in the descending vasa recta; all are glycoproteins. These transporters are crucial to the kidney's ability to concentrate urine. UT-A1 and UT-A3 are acutely regulated by vasopressin. UT-A1 has also been shown to be regulated by hypertonicity, angiotensin II, and oxytocin. Acute regulation of these transporters is through phosphorylation. Both UT-A1 and UT-A3 rapidly accumulate in the plasma membrane in response to stimulation by vasopressin or hypertonicity. Long-term regulation involves altering protein abundance in response to changes in hydration status, low protein diets, adrenal steroids, sustained diuresis, or antidiuresis. Urea transporters have been studied using animal models of disease including diabetes mellitus, lithium intoxication, hypertension, and nephrotoxic drug responses. Exciting new animal models are being developed to study these transporters and search for active urea transporters. Here we introduce urea and describe the current knowledge of the urea transporter proteins, their regulation, and their role in the kidney.
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Affiliation(s)
- Janet D Klein
- Renal Division, Department of Medicine, Emory University, Atlanta, Georgia, USA
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Schenk LK, Rinschen MM, Klokkers J, Kurian SM, Neugebauer U, Salomon DR, Pavenstaedt H, Schlatter E, Edemir B. Cyclosporin-A induced toxicity in rat renal collecting duct cells: interference with enhanced hypertonicity induced apoptosis. Cell Physiol Biochem 2011; 26:887-900. [PMID: 21220920 DOI: 10.1159/000323998] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/17/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Rat renal inner medullary collecting duct (IMCD) cells are physiologically exposed to a wide range of ambient tonicity. To maintain their function upon changes in osmolality, IMCD cells induce expression of osmoprotective and antiapoptotic genes, mainly mediated by the transcription factor Tonicity Enhancer Binding Protein (TonEBP). Some drugs like Cyclosporin-A (CsA) are discussed to interfere with the activity of TonEBP and thereby mediate their nephrotoxic effects. The aim of our study was to further understand CsA toxicity during elevation of ambient osmolality. METHODS First we examined cytotoxicity of CsA in IMCD exposed to elevated tonicity. Employing microarray analysis of gene expression, real-time PCR and immunoassays, we scrutinized pathways contributing to this effect. RESULTS We show that in IMCD cells CsA but not FK506 increases apoptosis upon an increase in tonicity. This effect is independent of cellular TonEBP localization or activity and reactive oxygen species. Microarray studies revealed marked quantitative differences in gene expression. Functional analysis showed overrepresentation of genes associated with cell death in presence of CsA. This correlated with increased mRNA expression of genes associated with the death receptor pathway and detection of TNFα in culture medium of cells treated with CsA. CONCLUSION Our results show that CsA cytotoxicity is induced under elevated ambient osmolality and that death receptor signaling probably contributes to CsA cytotoxicity.
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Affiliation(s)
- Laura K Schenk
- Department of Internal Medicine D, Experimental Nephrology, University of Muenster, Muenster, Germany
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Abstract
PURPOSE OF REVIEW Internal environment regulation, particularly volume and osmoregulation, has been a fundamental concept important to physiologists and clinicians for almost two centuries. Na balance, intracellular K homeostasis, the crucial role of the Na,K-ATPase pump, osmotic forces, and the overriding effect of the kidney on maintaining homeostasis are notions that have been taught by many and accepted by most for over 50 years. Nevertheless, contradictory findings, problems with simplistic balance explanations, and the notion of salt-sensitive and salt-resistant hypertension have been nagging headaches in the straightforward, two-compartment model of electrolyte balance. RECENT FINDINGS Na can be accumulated without commensurate water retention in the interstitium of the skin, and this skin Na storage is paralleled by increased polymerization and sulfation of glycosaminoglycans in the Na reservoir. Subcutaneous tissue macrophages express the transcription factor tonicity enhancer binding protein in response to Na-mediated interstitial osmotic stress and thereby secrete vascular endothelial growth factor C, which stimulates lymphatic formation and endothelial nitric oxide synthase expression, suggesting that the immune system is a regulator of volume and blood pressure homeostasis. SUMMARY Our findings do not abrogate the notion of pressure natriuresis and renal regulatory function. However, we do suggest that extracellular Na, volume and blood pressure homeostasis cannot be maintained without extrarenal regulatory mechanisms.
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