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Cheng YJG, Chen CC, Cheng CJ. Postnatal renal tubule development: roles of tubular flow and flux. Curr Opin Nephrol Hypertens 2024; 33:518-525. [PMID: 38913022 PMCID: PMC11290981 DOI: 10.1097/mnh.0000000000001007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/25/2024]
Abstract
PURPOSE OF REVIEW Postnatal renal tubule development is critical to adult kidney function. Several postnatal changes regulate the differentiation and proliferation of renal tubular cells. Here, we review the literature and our efforts on thick ascending limb (TAL) development in Bartter syndrome (BS). RECENT FINDINGS Glomerular filtrate quickly increases after birth, imposing fluid shear stress and circumferential stretch on immature renal tubules. Recent studies showed that kidney organoids under flow (superfusion) have better development of tubular structures and the expression of cilia and solute transporters. These effects are likely mediated by mechanosensors, such as cilia and the piezo1 channel. Improved renal oxygenation and sodium pump-dependent active transport can stimulate mitochondrial respiration and biogenesis. The functional coupling between transport and mitochondria ensures ATP supply for energy-demanding reactions in tubular cells, including cell cycle progression and proliferation. We recently discovered that postnatal renal medulla maturation and TAL elongation are impaired in Clc-k2-deficient BS mice. Primary cultured Clc-k2-deficient TAL cells have G1-S transition and proliferation delay. These developmental defects could be part of the early pathogenesis of BS and worsen the phenotype. SUMMARY Understanding how tubular flow and transepithelial ion fluxes regulate renal tubule development may improve the treatment of congenital renal tubulopathies.
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Affiliation(s)
- Yi-Jing G. Cheng
- Division of Nephrology, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, U.S.A
| | - Chien-Chou Chen
- Division of Nephrology, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei 114, Taiwan
| | - Chih-Jen Cheng
- Division of Nephrology, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, U.S.A
- Division of Nephrology, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei 114, Taiwan
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2
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Cheng YYW, Cheng CJ. Mitochondrial bioenergetics: coupling of transport to tubular mitochondrial metabolism. Curr Opin Nephrol Hypertens 2024; 33:405-413. [PMID: 38573234 PMCID: PMC11145760 DOI: 10.1097/mnh.0000000000000986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2024]
Abstract
PURPOSE OF REVIEW Renal tubules have robust active transport and mitochondrial metabolism, which are functionally coupled to maintain energy homeostasis. Here, I review the current literature and our recent efforts to examine mitochondrial adaptation to different transport activities in renal tubules. RECENT FINDINGS The advance of extracellular flux analysis (EFA) allows real-time assessments of mitochondrial respiration, glycolysis, and oxidation of energy substrates. We applied EFA assays to freshly isolated mouse proximal tubules, thick ascending limbs (TALs), and distal convoluted tubules (DCTs) and successfully differentiated their unique metabolic features. We found that TALs and DCTs adjusted their mitochondrial bioenergetics and biogenesis in response to acute and chronic alterations of transport activity. Based on the literature and our recent findings, I discuss working models and mechanisms underlying acute and chronic tubular adaptations to transport activity. The potential roles of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), AMP-activated protein kinase (AMPK), and uncoupling protein 2 (UCP2) are discussed. SUMMARY Mitochondria in renal tubules are highly plastic to accommodate different transport activities. Understanding the mechanisms may improve the treatment of renal tubulopathies.
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Affiliation(s)
- Yong-Yao W. Cheng
- Division of Nephrology, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Chih-Jen Cheng
- Division of Nephrology, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
- Division of Nephrology, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
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3
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Cheng CJ, Nizar JM, Dai DF, Huang CL. Transport activity regulates mitochondrial bioenergetics and biogenesis in renal tubules. FASEB J 2024; 38:e23703. [PMID: 38805156 PMCID: PMC11147170 DOI: 10.1096/fj.202400358rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Revised: 05/07/2024] [Accepted: 05/13/2024] [Indexed: 05/29/2024]
Abstract
Renal tubules are featured with copious mitochondria and robust transport activity. Mutations in mitochondrial genes cause congenital renal tubulopathies, and changes in transport activity affect mitochondrial morphology, suggesting mitochondrial function and transport activity are tightly coupled. Current methods of using bulk kidney tissues or cultured cells to study mitochondrial bioenergetics are limited. Here, we optimized an extracellular flux analysis (EFA) to study mitochondrial respiration and energy metabolism using microdissected mouse renal tubule segments. EFA detects mitochondrial respiration and glycolysis by measuring oxygen consumption and extracellular acidification rates, respectively. We show that both measurements positively correlate with sample sizes of a few centimeter-length renal tubules. The thick ascending limbs (TALs) and distal convoluted tubules (DCTs) critically utilize glucose/pyruvate as energy substrates, whereas proximal tubules (PTs) are significantly much less so. Acute inhibition of TALs' transport activity by ouabain treatment reduces basal and ATP-linked mitochondrial respiration. Chronic inhibition of transport activity by 2-week furosemide treatment or deletion of with-no-lysine kinase 4 (Wnk4) decreases maximal mitochondrial capacity. In addition, chronic inhibition downregulates mitochondrial DNA mass and mitochondrial length/density in TALs and DCTs. Conversely, gain-of-function Wnk4 mutation increases maximal mitochondrial capacity and mitochondrial length/density without increasing mitochondrial DNA mass. In conclusion, EFA is a sensitive and reliable method to investigate mitochondrial functions in isolated renal tubules. Transport activity tightly regulates mitochondrial bioenergetics and biogenesis to meet the energy demand in renal tubules. The system allows future investigation into whether and how mitochondria contribute to tubular remodeling adapted to changes in transport activity.
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Affiliation(s)
- Chih-Jen Cheng
- Division of Nephrology, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, U.S.A
- Division of Nephrology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Jonathan M Nizar
- Division of Nephrology, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, U.S.A
| | - Dao-Fu Dai
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, U.S.A
| | - Chou-Long Huang
- Division of Nephrology, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, U.S.A
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4
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Cheng CJ, Nizar JM, Dai DF, Huang CL. Transport activity regulates mitochondrial bioenergetics and biogenesis in renal tubules. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.04.578838. [PMID: 38370657 PMCID: PMC10871199 DOI: 10.1101/2024.02.04.578838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Renal tubules are featured with copious mitochondria and robust transport activity. Mutations in mitochondrial genes cause congenital renal tubulopathies, and changes in transport activity affect mitochondrial morphology, suggesting mitochondrial function and transport activity are tightly coupled. Current methods of using bulk kidney tissues or cultured cells to study mitochondrial bioenergetics are limited. Here, we optimized an extracellular flux analysis (EFA) to study mitochondrial respiration and energy metabolism using microdissected mouse renal tubule segments. EFA detects mitochondrial respiration and glycolysis by measuring oxygen consumption and extracellular acidification rates, respectively. We show that both measurements positively correlate with sample sizes of a few centimeter-length renal tubules. The thick ascending limbs (TALs) and distal convoluted tubules (DCTs) predominantly utilize glucose/pyruvate as energy substrates, whereas proximal tubules (PTs) are significantly much less so. Acute inhibition of TALs' transport activity by ouabain treatment reduces basal and ATP-linked mitochondrial respiration. Chronic inhibition of transport activity by 2-week furosemide treatment or deletion of with-no-lysine kinase 4 (Wnk4) decreases maximal mitochondrial capacity. In addition, chronic inhibition downregulates mitochondrial DNA mass and mitochondrial length/density in TALs and DCTs. Conversely, gain-of-function Wnk4 mutation increases maximal mitochondrial capacity and mitochondrial length/density without increasing mitochondrial DNA mass. In conclusion, EFA is a sensitive and reliable method to investigate mitochondrial functions in isolated renal tubules. Transport activity tightly regulates mitochondrial bioenergetics and biogenesis to meet the energy demand in renal tubules. The system allows future investigation into whether and how mitochondria contribute to tubular remodeling adapted to changes in transport activity. Key points A positive correlation between salt reabsorption and oxygen consumption in mammalian kidneys hints at a potential interaction between transport activity and mitochondrial respiration in renal tubules.Renal tubules are heterogeneous in transport activity and mitochondrial metabolism, and traditional assays using bulk kidney tissues cannot provide segment-specific information.Here, we applied an extracellular flux analysis to investigate mitochondrial respiration and energy metabolism in isolated renal tubules. This assay is sensitive in detecting oxygen consumption and acid production in centimeter-length renal tubules and reliably recapitulates segment-specific metabolic features.Acute inhibition of transport activity reduces basal and ATP-linked mitochondrial respirations without changing maximal mitochondrial respiratory capacity. Chronic alterations of transport activity further adjust maximal mitochondrial respiratory capacity via regulating mitochondrial biogenesis or non-transcriptional mechanisms.Our findings support the concept that renal tubular cells finely adjust mitochondrial bioenergetics and biogenesis to match the new steady state of transport activity.
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5
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Li Y, Gu W, Hepokoski M, Pham H, Tham R, Kim YC, Simonson TS, Singh P. Energy Metabolism Dysregulation in Chronic Kidney Disease. KIDNEY360 2023; 4:1080-1094. [PMID: 37222594 PMCID: PMC10476685 DOI: 10.34067/kid.0000000000000153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 05/08/2023] [Indexed: 05/25/2023]
Abstract
Key Points There is significant enrichment in metabolic pathways in early stages in the subtotal nephrectomy model of CKD. Proximal tubular mitochondrial respiration is suppressed likely from mitochondrial dysfunction in substrate utilization and ATP synthesis. There is significant suppression of pyruvate dehydrogenase and increased glycolysis in proximal tubules. Background CKD is a significant contributor to morbidity and mortality. A better understanding of mechanisms underlying CKD progression is indispensable for developing effective therapies. Toward this goal, we addressed specific gaps in knowledge regarding tubular metabolism in the pathogenesis of CKD using the subtotal nephrectomy (STN) model in mice. Methods Weight- and age‐matched male 129X1/SvJ mice underwent sham or STN surgeries. We conducted serial GFR and hemodynamic measurements up to 16 weeks after sham and STN surgery and established the 4-week time point for subsequent studies. Results For a comprehensive assessment of renal metabolism, we conducted transcriptomic analyses, which showed significant enrichment of pathways involved in fatty acid metabolism, gluconeogenesis, glycolysis, and mitochondrial metabolism in STN kidneys. Expression of rate-limiting fatty acid oxidation and glycolytic enzymes was increased in STN kidneys, and proximal tubules in STN kidneys exhibited increased functional glycolysis but decreased mitochondrial respiration, despite an increase in mitochondrial biogenesis. Assessment of the pyruvate dehydrogenase complex pathway showed significant suppression of pyruvate dehydrogenase, suggesting decreased provision of acetyl CoA from pyruvate for the citric acid cycle to fuel mitochondrial respiration. Conclusion Metabolic pathways are significantly altered in response to kidney injury and may play an important role in the disease progression.
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Affiliation(s)
- Ying Li
- Division of Nephrology and Hypertension, University of California San Diego, San Diego, California
- VA San Diego Healthcare System, San Diego, California
| | - Wanjun Gu
- Division of Pulmonary, Critical Care and Sleep Medicine, University of California San Diego, San Diego, California
| | - Mark Hepokoski
- VA San Diego Healthcare System, San Diego, California
- Division of Pulmonary, Critical Care and Sleep Medicine, University of California San Diego, San Diego, California
| | - Hai Pham
- Division of Nephrology and Hypertension, University of California San Diego, San Diego, California
- VA San Diego Healthcare System, San Diego, California
| | - Rick Tham
- Division of Nephrology and Hypertension, University of California San Diego, San Diego, California
- VA San Diego Healthcare System, San Diego, California
| | - Young Chul Kim
- Division of Nephrology and Hypertension, University of California San Diego, San Diego, California
- VA San Diego Healthcare System, San Diego, California
| | - Tatum S. Simonson
- Division of Pulmonary, Critical Care and Sleep Medicine, University of California San Diego, San Diego, California
| | - Prabhleen Singh
- Division of Nephrology and Hypertension, University of California San Diego, San Diego, California
- VA San Diego Healthcare System, San Diego, California
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6
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Hall AM, de Seigneux S. Metabolic mechanisms of acute proximal tubular injury. Pflugers Arch 2022; 474:813-827. [PMID: 35567641 PMCID: PMC9338906 DOI: 10.1007/s00424-022-02701-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 04/12/2022] [Accepted: 05/02/2022] [Indexed: 12/11/2022]
Abstract
Damage to the proximal tubule (PT) is the most frequent cause of acute kidney injury (AKI) in humans. Diagnostic and treatment options for AKI are currently limited, and a deeper understanding of pathogenic mechanisms at a cellular level is required to rectify this situation. Metabolism in the PT is complex and closely coupled to solute transport function. Recent studies have shown that major changes in PT metabolism occur during AKI and have highlighted some potential targets for intervention. However, translating these insights into effective new therapies still represents a substantial challenge. In this article, in addition to providing a brief overview of the current state of the field, we will highlight three emerging areas that we feel are worthy of greater attention. First, we will discuss the role of axial heterogeneity in cellular function along the PT in determining baseline susceptibility to different metabolic hits. Second, we will emphasize that elucidating insult specific pathogenic mechanisms will likely be critical in devising more personalized treatments for AKI. Finally, we will argue that uncovering links between tubular metabolism and whole-body homeostasis will identify new strategies to try to reduce the considerable morbidity and mortality associated with AKI. These concepts will be illustrated by examples of recent studies emanating from the authors' laboratories and performed under the auspices of the Swiss National Competence Center for Kidney Research (NCCR Kidney.ch).
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Affiliation(s)
- Andrew M Hall
- Institute of Anatomy, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
- Department of Nephrology, University Hospital Zurich, Zurich, Switzerland.
| | - Sophie de Seigneux
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
- Department of Medicine, Service of Nephrology, Geneva University Hospitals, Geneva, Switzerland
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Chen Y, Li J, Yuan P, Wu Z, Wang Z, Wu W. Graphene oxide promoted chromium uptake by zebrafish embryos with multiple effects: Adsorption, bioenergetic flux and metabolism. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 802:149914. [PMID: 34474293 DOI: 10.1016/j.scitotenv.2021.149914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 08/22/2021] [Accepted: 08/22/2021] [Indexed: 06/13/2023]
Abstract
The increasing production and application of graphene oxide (GO, a popular carbon nanomaterial), makes their release into aqueous environment inevitably. The capability of GO to enhance the toxicity of background contaminants has been widely concerned. However, the effect of GO on heavy metal accumulation in fish embryos remains unclear. Here, we show that GO-promoted chromium (Cr) uptake by zebrafish embryos with multiple effects. The adsorption accelerated the aggregation and settlement of Cr6+-adsorbed GO and decreased the Cr6+ concentration in the upper water, which enhanced the interaction of chorions and contaminants (Cr6+, GO and Cr6+-adsorbed GO). In the presence of GO, the Cr content in chorions and intra-chorion embryos was increased by four times and 57% respectively, compared to that of the single Cr6+ exposure. Furthermore, GO+Cr6+ increased the oxygen consumption rates, embryonic acid extrusion rates and ATP production, induced more serious oxidative stress, and disturbed amino acid metabolism, fatty acid metabolism and TCA cycle. These findings provide new insights into the effect of GO on heavy metal bioaccumulation and toxicity during embryogenesis.
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Affiliation(s)
- Yuming Chen
- School of Public Health, Xinxiang Medical University, Xinxiang 453003, China
| | - Jitong Li
- Henan Provincial Key Laboratory of Children's Genetics and Metabolic Diseases/Henan Neural Development Engineering Research Center for Children, Department of Nephrology and Rheumatology, Children's Hospital Affiliated to Zhengzhou University, Zhengzhou 450018, China
| | - Peng Yuan
- School of Public Health, Xinxiang Medical University, Xinxiang 453003, China.
| | - Zhineng Wu
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401, China
| | - Zhaoxin Wang
- School of Public Health, Xinxiang Medical University, Xinxiang 453003, China
| | - Weidong Wu
- School of Public Health, Xinxiang Medical University, Xinxiang 453003, China
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8
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Zandona A, Maraković N, Mišetić P, Madunić J, Miš K, Padovan J, Pirkmajer S, Katalinić M. Activation of (un)regulated cell death as a new perspective for bispyridinium and imidazolium oximes. Arch Toxicol 2021; 95:2737-2754. [PMID: 34173857 DOI: 10.1007/s00204-021-03098-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 06/15/2021] [Indexed: 12/20/2022]
Abstract
Oximes, investigated as antidotes against organophosphates (OP) poisoning, are known to display toxic effects on a cellular level, which could be explained beyond action on acetylcholinesterase as their main target. To investigate this further, we performed an in vitro cell-based evaluation of effects of two structurally diverse oxime groups at concentrations of up to 800 μM, on several cell models: skeletal muscle, kidney, liver, and neural cells. As indicated by our results, compounds with an imidazolium core induced necrosis, unregulated cell death characterized by a cell burst, increased formation of reactive oxygen species, and activation of antioxidant scavenging. On the other hand, oximes with a pyridinium core activated apoptosis through specific caspases 3, 8, and/or 9. Interestingly, some of the compounds exhibited a synergistic effect. Moreover, we generated a pharmacophore model for each oxime series and identified ligands from public databases that map to generated pharmacophores. Several interesting hits were obtained including chemotherapeutics and specific inhibitors. We were able to define the possible structural features of tested oximes triggering toxic effects: chlorine atoms in combination with but-2(E)-en-1,4-diyl linker and adding a second benzene ring with substituents such as chlorine and/or methyl on the imidazolium core. Such oximes could not be used in further OP antidote development research, but could be introduced in other research studies on new specific targets. This could undoubtedly result in an overall improved wider use of unexplored oxime database created so far in OP antidotes field of research in a completely new perspective.
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Affiliation(s)
- Antonio Zandona
- Institute for Medical Research and Occupational Health, POB 291, 10001, Zagreb, Croatia
| | - Nikola Maraković
- Institute for Medical Research and Occupational Health, POB 291, 10001, Zagreb, Croatia
| | | | - Josip Madunić
- Institute for Medical Research and Occupational Health, POB 291, 10001, Zagreb, Croatia
| | - Katarina Miš
- Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia
| | | | - Sergej Pirkmajer
- Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia
| | - Maja Katalinić
- Institute for Medical Research and Occupational Health, POB 291, 10001, Zagreb, Croatia.
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Abstract
Metabolic reprogramming is one of the major steps that tumor cells take during cancer progression. This process allows the cells to survive in a nutrient- and oxygen-deprived environment, to become stress tolerant, and to metastasize to different sites. Recent studies have shown that reprogramming happens in stromal cells and involves the cross-talk of the cancer cell/tumor microenvironment. There are similarities between the metabolic reprogramming that occurs in both noncancerous kidney diseases and renal cell carcinoma (RCC), suggesting that such reprogramming is a means by which renal epithelial cells survive injury and repair the tissue, and that RCC cells hijack this system. This article reviews reprogramming of major metabolism pathways in RCC, highlighting similarities and differences from kidney diseases and potential therapeutic strategies against it.
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10
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Li Y, Nourbakhsh N, Pham H, Tham R, Zuckerman JE, Singh P. Evolution of altered tubular metabolism and mitochondrial function in sepsis-associated acute kidney injury. Am J Physiol Renal Physiol 2020; 319:F229-F244. [PMID: 32538150 DOI: 10.1152/ajprenal.00390.2019] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Sepsis-associated acute kidney injury (s-AKI) has a staggering impact in patients and lacks any treatment. Incomplete understanding of the pathogenesis of s-AKI is a major barrier to the development of effective therapies. We address the gaps in knowledge regarding renal oxygenation, tubular metabolism, and mitochondrial function in the pathogenesis of s-AKI using the cecal ligation and puncture (CLP) model in mice. At 24 h after CLP, renal oxygen delivery was reduced; however, fractional oxygen extraction was unchanged, suggesting inefficient renal oxygen utilization despite decreased glomerular filtration rate and filtered load. To investigate the underlying mechanisms, we examined temporal changes in mitochondrial function and metabolism at 4 and 24 h after CLP. At 4 h after CLP, markers of mitochondrial content and biogenesis were increased in CLP kidneys, but mitochondrial oxygen consumption rates were suppressed in proximal tubules. Interestingly, at 24 h, proximal tubular mitochondria displayed high respiratory capacity, but with decreased mitochondrial content, biogenesis, fusion, and ATP levels in CLP kidneys, suggesting decreased ATP synthesis efficiency. We further investigated metabolic reprogramming after CLP and observed reduced expression of fatty acid oxidation enzymes but increased expression of glycolytic enzymes at 24 h. However, assessment of functional glycolysis revealed lower glycolytic capacity, glycolytic reserve, and compensatory glycolysis in CLP proximal tubules, which may explain their susceptibility to injury. In conclusion, we demonstrated significant alterations in renal oxygenation, tubular mitochondrial function, and metabolic reprogramming in s-AKI, which may play an important role in the progression of injury and recovery from AKI in sepsis.
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Affiliation(s)
- Ying Li
- Division of Nephrology-Hypertension, University of California, San Diego, California.,Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Noureddin Nourbakhsh
- Division of Nephrology-Hypertension, University of California, San Diego, California.,Division of Pediatric Nephrology, Rady Children's Hospital San Diego, University of California, San Diego, California
| | - Hai Pham
- Division of Nephrology-Hypertension, University of California, San Diego, California.,Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Rick Tham
- Division of Nephrology-Hypertension, University of California, San Diego, California.,Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Jonathan E Zuckerman
- Department of Pathology and Laboratory Medicine, University of California, Los Angeles, California
| | - Prabhleen Singh
- Division of Nephrology-Hypertension, University of California, San Diego, California.,Veterans Affairs San Diego Healthcare System, San Diego, California
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11
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Jang HS, Noh MR, Kim J, Padanilam BJ. Defective Mitochondrial Fatty Acid Oxidation and Lipotoxicity in Kidney Diseases. Front Med (Lausanne) 2020; 7:65. [PMID: 32226789 PMCID: PMC7080698 DOI: 10.3389/fmed.2020.00065] [Citation(s) in RCA: 93] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Accepted: 02/13/2020] [Indexed: 12/31/2022] Open
Abstract
The kidney is a highly metabolic organ and uses high levels of ATP to maintain electrolyte and acid-base homeostasis and reabsorb nutrients. Energy depletion is a critical factor in development and progression of various kidney diseases including acute kidney injury (AKI), chronic kidney disease (CKD), and diabetic and glomerular nephropathy. Mitochondrial fatty acid β-oxidation (FAO) serves as the preferred source of ATP in the kidney and its dysfunction results in ATP depletion and lipotoxicity to elicit tubular injury and inflammation and subsequent fibrosis progression. This review explores the current state of knowledge on the role of mitochondrial FAO dysfunction in the pathophysiology of kidney diseases including AKI and CKD and prospective views on developing therapeutic interventions based on mitochondrial energy metabolism.
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Affiliation(s)
- Hee-Seong Jang
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE, United States
| | - Mi Ra Noh
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE, United States
| | - Jinu Kim
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE, United States.,Department of Anatomy, Jeju National University School of Medicine, Jeju, South Korea.,Interdisciplinary Graduate Program in Advanced Convergence Technology & Science, Jeju National University, Jeju, South Korea
| | - Babu J Padanilam
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE, United States.,Internal Medicine, Section of Nephrology, University of Nebraska Medical Center, Omaha, NE, United States
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12
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Dibo P, Marañón RO, Chandrashekar K, Mazzuferi F, Silva GB, Juncos LA, Juncos LI. Angiotensin-(1-7) inhibits sodium transport via Mas receptor by increasing nitric oxide production in thick ascending limb. Physiol Rep 2019; 7:e14015. [PMID: 30839176 PMCID: PMC6401662 DOI: 10.14814/phy2.14015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 02/03/2019] [Indexed: 02/07/2023] Open
Abstract
Sodium transport in the thick ascending loop of Henle (TAL) is tightly regulated by numerous factors, especially angiotensin II (Ang II), a key end-product of the renin-angiotensin system (RAS). However, an alternative end-product of the RAS, angiotensin-(1-7) [Ang-(1-7)], may counter some of the Ang II actions. Indeed, it causes vasodilation and promotes natriuresis through its effects in the proximal and distal tubule. However, its effects on the TAL are unknown. Because the TAL expresses the Mas receptor, an Ang-(1-7) ligand, which in turn may increase NO and inhibit Na+ transport, we hypothesized that Ang-(1-7) inhibits Na transport in the TAL, via a Mas receptor/NO-dependent mechanism. We tested this by measuring transport-dependent oxygen consumption (VO2 ) in TAL suspensions. Administering Ang-(1-7) decreased VO2 ; an effect prevented by dimethyl amiloride and furosemide, signifying that Ang-(1-7) inhibits transport-dependent VO2 in TAL. Ang-(1-7) also increased NO levels, known inhibitors of Na+ transport in the TAL. The effects of Ang-(1-7) on VO2 , as well as on NO levels, were ameliorated by the Mas receptor antagonist, D-Ala, in effect suggesting that Ang-(1-7) may inhibit transport-dependent VO2 in TAL via Mas receptor-dependent activation of the NO pathway. Indeed, blocking NO synthesis with L-NAME prevented the inhibitory actions of Ang-(1-7) on VO2 . Our data suggest that Ang-(1-7) may modulate TAL Na+ transport via Mas receptor-dependent increases in NO leading to the inhibition of transport activity.
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Affiliation(s)
- Paula Dibo
- Department of Basic ResearchJ. Robert Cade FoundationCordobaArgentina
| | - Rodrigo O. Marañón
- Department of Medicine/NephrologyUniversity of Mississippi Medical CenterJacksonMississippi
- Department of Cell and Molecular BiologyUniversity of Mississippi Medical CenterJacksonMississippi
| | - Kiran Chandrashekar
- Department of Medicine/NephrologyCentral Arkansas Veterans Healthcare SystemUniversity of Arkansas for Medical SciencesLittle RockArkansas
| | | | - Guillermo B. Silva
- Department of Basic ResearchJ. Robert Cade FoundationCordobaArgentina
- Gabinete de Tecnología Médica (GATEME‐UNSJ)Universidad Nacional de San Juan ‐ Consejo Nacional de Investigaciones Científicas y Técnicas – CONICETSan JuanArgentina
| | - Luis A. Juncos
- Department of Medicine/NephrologyCentral Arkansas Veterans Healthcare SystemUniversity of Arkansas for Medical SciencesLittle RockArkansas
| | - Luis I. Juncos
- Department of Basic ResearchJ. Robert Cade FoundationCordobaArgentina
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13
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Zhang X, Zhu C, Gao J, Mei F, Yin J, Bu L, Cheng X, Sheng C, Qu S. Gender difference in the relationship between serum uric acid reduction and improvement in body fat distribution after laparoscopic sleeve gastrectomy in Chinese obese patients: a 6-month follow-up. Lipids Health Dis 2018; 17:288. [PMID: 30572901 PMCID: PMC6302487 DOI: 10.1186/s12944-018-0934-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 11/28/2018] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Hyperuricemia is related to obesity and fat accumulation. This study aimed to observe the effects of laparoscopic sleeve gastrectomy (LSG) on serum uric acid (sUA) level and body fat distribution in obese patients. The relationships between post-LSG improvement in sUA levels and body fat distribution changes, as well as their sex-related differences, were also explored. METHODS In total, 128 obese patients (48 men; 80 women) who underwent LSG were enrolled. Anthropometric indicators, glucose and lipid metabolic indicators, and sUA levels were measured pre-LSG and 6 months post-LSG. The body compositions were measured via dual-energy X-ray absorptiometry. The patients were divided into normal-sUA (NUA) and high-sUA (HUA) groups based on preoperative sUA levels. RESULTS Compared with the NUA group, the reduction of sUA levels 6 months post-LSG was more significant in the HUA group. In addition, sUA reduction in the female HUA group was more significant than that of the male HUA group (P < 0.01). Changes in serum uric acid levels (ΔsUA) in the male HUA group was positively correlated with changes in body weight, body mass index, neck circumference, and hip circumference (r = 0.618, 0.653, 0.716, and 0.501, respectively; P < 0.05 in all cases). It was also positively correlated with changes in fat mass in the gynoid region, android region, and legs, (r = 0.675, 0.551, and 0.712, respectively; P < 0.05 in all cases), and negatively correlated with changes in total testosterone (ΔTT) (r = - 0.517; P = 0.040). Furthermore, ΔTT in this group was closely associated with the improved sex-related fat distribution. The ΔsUA in the female HUA group was positively correlated with changes in fasting serum C peptide and ΔLNIR (r = 0.449 and 0.449, respectively; P < 0.05 in both cases). In addition, it was also positively correlated with changes in visceral adipose tissue (VAT) fat mass, VAT fat volume, and VAT fat area (r = 0.749, 0.749, and 0.747, respectively; P < 0.01 in all cases). CONCLUSIONS sUA levels of obese patients with hyperuricemia improved 6 months after LSG. Reduction of sUA after LSG was correlated with improved body fat distribution, and the relationships also displayed sex-based differences. Uric acid might be an important metabolic regulator associated with fat distribution and sex hormones.
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Affiliation(s)
- Xuane Zhang
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, Tongji University School of Medicine, No.301 Middle Yanchang Road, Shanghai, 200072, China
- Department of Endocrinology and Metabolism, YangPu Hospital, Tongji University School of Medicine, Shanghai, 200090, China
| | - Cuiling Zhu
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, Tongji University School of Medicine, No.301 Middle Yanchang Road, Shanghai, 200072, China
| | - Jingyang Gao
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, Tongji University School of Medicine, No.301 Middle Yanchang Road, Shanghai, 200072, China
| | - Fangyun Mei
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, Tongji University School of Medicine, No.301 Middle Yanchang Road, Shanghai, 200072, China
| | - Jiajing Yin
- National Metabolic Management Center (Shanghai 10th People's Hospital), Shanghai, 200072, China
| | - Le Bu
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, Tongji University School of Medicine, No.301 Middle Yanchang Road, Shanghai, 200072, China
| | - Xiaoyun Cheng
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, Tongji University School of Medicine, No.301 Middle Yanchang Road, Shanghai, 200072, China
| | - Chunjun Sheng
- National Metabolic Management Center (Shanghai 10th People's Hospital), Shanghai, 200072, China
| | - Shen Qu
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, Tongji University School of Medicine, No.301 Middle Yanchang Road, Shanghai, 200072, China.
- National Metabolic Management Center (Shanghai 10th People's Hospital), Shanghai, 200072, China.
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14
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Angiotensin II-induced hypertension in rats is only transiently accompanied by lower renal oxygenation. Sci Rep 2018; 8:16342. [PMID: 30397212 PMCID: PMC6218546 DOI: 10.1038/s41598-018-34211-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 10/09/2018] [Indexed: 02/08/2023] Open
Abstract
Activation of the renin-angiotensin system may initiate chronic kidney disease. We hypothesised that renal hypoxia is a consequence of hemodynamic changes induced by angiotensin II and occurs prior to development of severe renal damage. Male Sprague-Dawley rats were infused continuously with angiotensin II (350 ng/kg/min) for 8 days. Mean arterial pressure (n = 5), cortical (n = 6) and medullary (n = 7) oxygenation (pO2) were continuously recorded by telemetry and renal tissue injury was scored. Angiotensin II increased arterial pressure gradually to 150 ± 18 mmHg. This was associated with transient reduction of oxygen levels in renal cortex (by 18 ± 2%) and medulla (by 17 ± 6%) at 10 ± 2 and 6 ± 1 hours, respectively after starting infusion. Thereafter oxygen levels normalised to pre-infusion levels and were maintained during the remainder of the infusion period. In rats receiving angiotensin II, adding losartan to drinking water (300 mg/L) only induced transient increase in renal oxygenation, despite normalisation of arterial pressure. In rats, renal hypoxia is only a transient phenomenon during initiation of angiotensin II-induced hypertension.
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15
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Schiffer TA, Gustafsson H, Palm F. Kidney outer medulla mitochondria are more efficient compared with cortex mitochondria as a strategy to sustain ATP production in a suboptimal environment. Am J Physiol Renal Physiol 2018; 315:F677-F681. [PMID: 29846107 DOI: 10.1152/ajprenal.00207.2018] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The kidneys receive ~25% of cardiac output, which is a prerequisite to maintain sufficient glomerular filtration rate. However, both intrarenal regional renal blood flow and tissue oxygen levels are heterogeneous with decreasing levels in the inner part of the medulla. These differences, in combination with the heterogeneous metabolic activity of the different nephron segment located in the different parts of the kidney, may constitute a functional problem when challenged. The proximal tubule and the medullary thick ascending limb of Henle are considered to have the highest metabolic rate, which is related to the high mitochondria content needed to sustain sufficient ATP production from oxidative phosphorylation to support high electrolyte transport activity in these nephron segments. Interestingly, the cells located in kidney medulla function at the verge of hypoxia, and the mitochondria may have adapted to the surrounding environment. However, little is known about intrarenal differences in mitochondria function. We therefore investigated functional differences between mitochondria isolated from kidney cortex and medulla of healthy normoglycemic rats by using high-resolution respirometry. The results demonstrate that medullary mitochondria had a higher degree of coupling, are more efficient, and have higher oxygen affinity, which would make them more suitable to function in an environment with limited oxygen supply. Furthermore, these results support the hypothesis that mitochondria of medullary cells have adapted to the normal hypoxic in vivo situation as a strategy of sustaining ATP production in a suboptimal environment.
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Affiliation(s)
- Tomas A Schiffer
- Department of Radiology Norrköping, Department of Medical and Health Sciences, Linköping University , Linköping , Sweden.,Department of Medical Cell Biology, Uppsala University , Uppsala , Sweden
| | - Håkan Gustafsson
- Department of Medical Cell Biology, Uppsala University , Uppsala , Sweden
| | - Fredrik Palm
- Department of Radiology Norrköping, Department of Medical and Health Sciences, Linköping University , Linköping , Sweden
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16
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Packialakshmi B, Zhou X. Experimental autoimmune encephalomyelitis (EAE) up-regulates the mitochondrial activity and manganese superoxide dismutase (MnSOD) in the mouse renal cortex. PLoS One 2018; 13:e0196277. [PMID: 29689072 PMCID: PMC5916489 DOI: 10.1371/journal.pone.0196277] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 04/10/2018] [Indexed: 12/19/2022] Open
Abstract
Increases of the activity of mitochondrial electron transport chain generally lead to increases of production of ATP and reactive oxygen species (ROS) as by-products. MnSOD is the first line of defense against the stress induced by mitochondrial ROS. Our previous studies demonstrated that EAE progression increased Na,K-ATPase activity in the mouse kidney cortex. Since mitochondria are the major source of ATP, our present studies were sought to determine whether EAE progression increased mitochondrial activity. We found that severe EAE increased mitochondrial complex II and IV activities without significantly affecting complex I activity with corresponding increases of ROS in the isolated mitochondria and native kidney cortex. Severe EAE augmented both cytosolic and mitochondrial MnSOD protein levels and activities and decreased the specific activity of mitochondrial MnSOD when the total mitochondrial MnSOD activity was normalized to the protein level. Using HEK293 cells as a model free of interference from immune reactions, we found that activation of Na,K-ATPase by monensin for 24 hours increased complex II activity, mitochondrial ROS and MnSOD protein abundance, and decreased the specific activity of the mitochondrial MnSOD. Inhibition of Na,K-ATPase by ouabain or catalase attenuated the effects of monensin on the mitochondrial complex II activity, ROS, MnSOD protein level and specific activity. Kockdown of MnSOD by RNAi reduced the mitochondrial ability to generate ATP. In conclusion, EAE increases mitochondrial activity possibly to meet the energy demand from increased Na,K-ATPase activity. EAE increases mitochondrial MnSOD protein abundance to compensate for the loss of the specific activity of the enzyme, thus minimizing the harmful effects of ROS.
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Affiliation(s)
- Balamurugan Packialakshmi
- Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Xiaoming Zhou
- Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
- * E-mail:
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17
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Abstract
The ex vivo kidney slice technique has been used extensively in the fields of kidney physiology and cell biology. Our group and others have used this method to study epithelial traffic of transport proteins in situ in kidney tissue. In this methodology chapter, we summarize our adaptation of this classic protocol for the study of the effect of AMPK in the modulation of transport protein regulation, especially in kidney epithelial cells. Briefly, slices were obtained by sectioning freshly harvested rodent (rat or mouse) kidneys using a Stadie-Riggs tissue slicer. The harvested kidney and the kidney slices are kept in a physiological buffer equilibrated with 5% CO2 at body temperature (37 °C) in the presence of different AMPK activating agents vs. vehicle control followed by rapid freezing or fixation of the slices to prevent non-specific AMPK activation. Thus, homogenates of these frozen slices can be used to study AMPK activation status in the tissue as well as the downstream effects of AMPK on kidney proteins via biochemical techniques, such as immunoblotting and immunoprecipitation. Alternatively, the fixed slices can be used to evaluate AMPK-mediated subcellular traffic changes of epithelial transport proteins via immunolabeling followed by confocal microscopy. The resulting micrographs can then be used for systematic quantification of AMPK-induced changes in subcellular localization of transport proteins.
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18
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Udwan K, Abed A, Roth I, Dizin E, Maillard M, Bettoni C, Loffing J, Wagner CA, Edwards A, Feraille E. Dietary sodium induces a redistribution of the tubular metabolic workload. J Physiol 2017; 595:6905-6922. [PMID: 28940314 PMCID: PMC5685825 DOI: 10.1113/jp274927] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 09/11/2017] [Indexed: 01/11/2023] Open
Abstract
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. 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.
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Affiliation(s)
- Khalil Udwan
- Department of Cellular Physiology and Metabolism, University of Geneva, CMU, 1 Rue Michel-Servet, CH-1211, Geneva 4, Switzerland.,National Centre of Competence in Research, NCCRKidney, CH, Switzerland
| | - Ahmed Abed
- Department of Cellular Physiology and Metabolism, University of Geneva, CMU, 1 Rue Michel-Servet, CH-1211, Geneva 4, Switzerland.,National Centre of Competence in Research, NCCRKidney, CH, Switzerland
| | - Isabelle Roth
- Department of Cellular Physiology and Metabolism, University of Geneva, CMU, 1 Rue Michel-Servet, CH-1211, Geneva 4, Switzerland
| | - Eva Dizin
- Department of Cellular Physiology and Metabolism, University of Geneva, CMU, 1 Rue Michel-Servet, CH-1211, Geneva 4, Switzerland.,National Centre of Competence in Research, NCCRKidney, CH, Switzerland
| | - Marc Maillard
- Centre hospitalier universitaire Vaudois, Service de néphrologie, CH-1011, Lausanne, Switzerland
| | - Carla Bettoni
- Institute of Physiology, University of Zürich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland
| | - Johannes Loffing
- Institute of Anatomy, University of Zürich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland.,National Centre of Competence in Research, NCCRKidney, CH, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zürich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland.,National Centre of Competence in Research, NCCRKidney, CH, Switzerland
| | - Aurélie Edwards
- Centre de Recherche des Cordeliers, INSERM UMRS1138 and CNRS ERL8228, 15 rue de l'Ecole de Médecine, F-75006, Paris, France.,Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Eric Feraille
- Department of Cellular Physiology and Metabolism, University of Geneva, CMU, 1 Rue Michel-Servet, CH-1211, Geneva 4, Switzerland.,National Centre of Competence in Research, NCCRKidney, CH, Switzerland
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19
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Nilsson KF, Sandin J, Gustafsson LE, Frithiof R. The novel nitric oxide donor PDNO attenuates ovine ischemia-reperfusion induced renal failure. Intensive Care Med Exp 2017; 5:29. [PMID: 28600797 PMCID: PMC5466578 DOI: 10.1186/s40635-017-0143-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 05/26/2017] [Indexed: 01/18/2023] Open
Abstract
Background Renal ischemia-reperfusion injury is a common cause of acute kidney injury in intensive care and surgery. Recently, novel organic mononitrites of 1,2-propanediol (PDNO) were synthesized and shown to rapidly and controllably deploy nitric oxide in the circulation when administered intravenously. We hypothesized that intravenous infusion of PDNO during renal ischemia reperfusion would improve post-ischemic renal function and microcirculation. Methods Sixteen sheep were anesthetized, mechanically ventilated, and surgically instrumented. The left renal artery was clamped for 90 min, and the effects of ischemia were studied for a total of 8 h. Fifteen minutes prior to the release of the clamp, intravenous infusions of PDNO (n = 8) or vehicle (1,2 propanediol + inorganic nitrite, n = 8) were initiated (180 nmol/kg/min for 30 min, thereafter 60 nmol/kg/min for the remainder of the experiment). Results Renal artery blood flow, cortical and medullary perfusion, and diuresis and creatinine clearance decreased in the left kidney post ischemia. However, in the sheep treated with PDNO, diuresis and creatinine clearance in the left kidney were significantly higher post ischemia compared to vehicle-treated animals (1.7 ± 0.5 vs 0.7 ± 0.3 ml/kg/h, p = 0.04 and 7.5 ± 2.1 vs 1.7 ± 0.6 ml/min, p = 0.02, respectively). Left renal medullary perfusion and oxygen uptake were higher in the PDNO group (73 ± 9 vs 37 ± 5% of baseline, p = 0.004 and 2.6 ± 0.4 vs 1.6 ± 0.3 ml/min, p = 0.02, respectively). PDNO significantly increased renal oxygen consumption and reduced the oxygen utilization for sodium reabsorption (p = 0.03 for both). Mean arterial blood pressure was significantly reduced by PDNO (83 ± 3 vs 94 ± 3 mmHg, p = 0.02) but was still within normal limits. Total renal blood flow was not affected, and there were no signs of increased blood methemoglobin concentrations or tachyphylaxis. Conclusions The novel nitric oxide donor PDNO improved renal function after ischemia. PDNO also prevented the persistent reduction in medullary perfusion during reperfusion and improved renal oxygen utilization without severe side effects.
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Affiliation(s)
- Kristofer F Nilsson
- Department of Cardiothoracic and Vascular Surgery, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.,Department of Physiology & Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - John Sandin
- Department of Physiology & Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Lars E Gustafsson
- Department of Physiology & Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Robert Frithiof
- Department of Physiology & Pharmacology, Karolinska Institutet, Stockholm, Sweden. .,Department of Surgical Sciences, Section of Anesthesia and Intensive Care, Uppsala University, Uppsala, Sweden.
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20
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Thomas JL, Pham H, Li Y, Hall E, Perkins GA, Ali SS, Patel HH, Singh P. Hypoxia-inducible factor-1α activation improves renal oxygenation and mitochondrial function in early chronic kidney disease. Am J Physiol Renal Physiol 2017; 313:F282-F290. [PMID: 28331062 DOI: 10.1152/ajprenal.00579.2016] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 03/17/2017] [Accepted: 03/20/2017] [Indexed: 02/07/2023] Open
Abstract
The pathophysiology of chronic kidney disease (CKD) is driven by alterations in surviving nephrons to sustain renal function with ongoing nephron loss. Oxygen supply-demand mismatch, due to hemodynamic adaptations, with resultant hypoxia, plays an important role in the pathophysiology in early CKD. We sought to investigate the underlying mechanisms of this mismatch. We utilized the subtotal nephrectomy (STN) model of CKD to investigate the alterations in renal oxygenation linked to sodium (Na) transport and mitochondrial function in the surviving nephrons. Oxygen delivery was significantly reduced in STN kidneys because of lower renal blood flow. Fractional oxygen extraction was significantly higher in STN. Tubular Na reabsorption was significantly lower per mole of oxygen consumed in STN. We hypothesized that decreased mitochondrial bioenergetic capacity may account for this and uncovered significant mitochondrial dysfunction in the early STN kidney: higher oxidative metabolism without an attendant increase in ATP levels, elevated superoxide levels, and alterations in mitochondrial morphology. We further investigated the effect of activation of hypoxia-inducible factor-1α (HIF-1α), a master regulator of cellular hypoxia response. We observed significant improvement in renal blood flow, glomerular filtration rate, and tubular Na reabsorption per mole of oxygen consumed with HIF-1α activation. Importantly, HIF-1α activation significantly lowered mitochondrial oxygen consumption and superoxide production and increased mitochondrial volume density. In conclusion, we report significant impairment of renal oxygenation and mitochondrial function at the early stages of CKD and demonstrate the beneficial role of HIF-1α activation on renal function and metabolism.
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Affiliation(s)
- Joanna L Thomas
- Department of Biomedical Engineering, School of Engineering, Mercer University, Macon, Georgia
| | - Hai Pham
- Division of Nephrology and Hypertension, Department of Medicine, University of California, San Diego, and VA San Diego Healthcare System, San Diego, California
| | - Ying Li
- Division of Nephrology and Hypertension, Department of Medicine, University of California, San Diego, and VA San Diego Healthcare System, San Diego, California
| | - Elanore Hall
- Division of Nephrology and Hypertension, Department of Medicine, University of California, San Diego, and VA San Diego Healthcare System, San Diego, California
| | - Guy A Perkins
- National Center for Microscopy and Imaging Research, La Jolla, California
| | - Sameh S Ali
- Center for Aging and Associated Diseases, Helmy Institute of Medical Science, Zewail City of Science and Technology, Giza, Egypt; and.,Department of Anesthesiology, University of California, San Diego, California and VA San Diego Healthcare System, San Diego, California
| | - Hemal H Patel
- Department of Anesthesiology, University of California, San Diego, California and VA San Diego Healthcare System, San Diego, California
| | - Prabhleen Singh
- Division of Nephrology and Hypertension, Department of Medicine, University of California, San Diego, and VA San Diego Healthcare System, San Diego, California;
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21
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Pedraza-Chaverri J, Sánchez-Lozada LG, Osorio-Alonso H, Tapia E, Scholze A. New Pathogenic Concepts and Therapeutic Approaches to Oxidative Stress in Chronic Kidney Disease. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2016; 2016:6043601. [PMID: 27429711 PMCID: PMC4939360 DOI: 10.1155/2016/6043601] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 05/16/2016] [Accepted: 05/25/2016] [Indexed: 12/24/2022]
Abstract
In chronic kidney disease inflammatory processes and stimulation of immune cells result in overproduction of free radicals. In combination with a reduced antioxidant capacity this causes oxidative stress. This review focuses on current pathogenic concepts of oxidative stress for the decline of kidney function and development of cardiovascular complications. We discuss the impact of mitochondrial alterations and dysfunction, a pathogenic role for hyperuricemia, and disturbances of vitamin D metabolism and signal transduction. Recent antioxidant therapy options including the use of vitamin D and pharmacologic therapies for hyperuricemia are discussed. Finally, we review some new therapy options in diabetic nephropathy including antidiabetic agents (noninsulin dependent), plant antioxidants, and food components as alternative antioxidant therapies.
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Affiliation(s)
| | - Laura G. Sánchez-Lozada
- Laboratory of Renal Physiopathology, INC Ignacio Chávez, 14080 Mexico City, DF, Mexico
- Department of Nephrology, INC Ignacio Chávez, 14080 Mexico City, DF, Mexico
| | - Horacio Osorio-Alonso
- Laboratory of Renal Physiopathology, INC Ignacio Chávez, 14080 Mexico City, DF, Mexico
- Department of Nephrology, INC Ignacio Chávez, 14080 Mexico City, DF, Mexico
| | - Edilia Tapia
- Laboratory of Renal Physiopathology, INC Ignacio Chávez, 14080 Mexico City, DF, Mexico
- Department of Nephrology, INC Ignacio Chávez, 14080 Mexico City, DF, Mexico
| | - Alexandra Scholze
- Department of Nephrology, Odense University Hospital, 5000 Odense, Denmark
- Institute of Clinical Research, University of Southern Denmark, 5000 Odense, Denmark
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22
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Umbro I, Gentile G, Tinti F, Muiesan P, Mitterhofer AP. Recent advances in pathophysiology and biomarkers of sepsis-induced acute kidney injury. J Infect 2015; 72:131-42. [PMID: 26702738 DOI: 10.1016/j.jinf.2015.11.008] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 11/24/2015] [Accepted: 11/28/2015] [Indexed: 12/26/2022]
Abstract
Sepsis is a complex clinical syndrome characterized by a systemic inflammatory response to an infective insult. This process often leads to widespread tissue injury and multiple organ dysfunction. In particular, the development of acute kidney injury (AKI) is one of the most frequent complications, which increases the complexity and cost of care, and is an independent risk factor for mortality. Previous suggestions highlighting systemic hypotension, renal vasoconstriction and ischaemia-reperfusion injury as the primary pathophysiological mechanisms involved in sepsis-induced AKI have been challenged. Recently it has been shown that sepsis-induced AKI occurs in the setting of microvascular dysfunction with release of microparticles, inflammation and energetic adaptation of highly metabolic organs to cellular stress. The intolerable high mortality rate associated with sepsis-induced AKI is partially explained by an incomplete understanding of its pathophysiology and a delay in diagnosis. The aim of this review is to focus on advances in understanding the sepsis pathophysiology, with particular attention to the fundamental mechanisms of sepsis-induced AKI and the potential diagnostic and prognostic markers involved.
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Affiliation(s)
- Ilaria Umbro
- The Liver Unit, Queen Elizabeth Hospital Birmingham, Mindelsohn Way, Edgbaston, B15 2GW Birmingham, United Kingdom; Department of Clinical Medicine, Nephrology and Dialysis B, Sapienza University of Rome, Viale dell'Università 37, 00185 Rome, Italy.
| | - Giuseppe Gentile
- Department of Cellular Biotechnologies and Hematology, Sapienza University of Rome, Via Benevento 6, 00185 Rome, Italy.
| | - Francesca Tinti
- The Liver Unit, Queen Elizabeth Hospital Birmingham, Mindelsohn Way, Edgbaston, B15 2GW Birmingham, United Kingdom; Department of Clinical Medicine, Nephrology and Dialysis B, Sapienza University of Rome, Viale dell'Università 37, 00185 Rome, Italy.
| | - Paolo Muiesan
- The Liver Unit, Queen Elizabeth Hospital Birmingham, Mindelsohn Way, Edgbaston, B15 2GW Birmingham, United Kingdom.
| | - Anna Paola Mitterhofer
- Department of Clinical Medicine, Nephrology and Dialysis B, Sapienza University of Rome, Viale dell'Università 37, 00185 Rome, Italy.
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Salehpour F, Ghanian Z, Yang C, Zheleznova NN, Kurth T, Dash RK, Cowley AW, Ranji M. Effects of p67phox on the mitochondrial oxidative state in the kidney of Dahl salt-sensitive rats: optical fluorescence 3-D cryoimaging. Am J Physiol Renal Physiol 2015; 309:F377-82. [PMID: 26062875 DOI: 10.1152/ajprenal.00098.2015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 06/09/2015] [Indexed: 02/07/2023] Open
Abstract
The goal of the present study was to quantify and correlate the contribution of the cytosolic p67(phox) subunit of NADPH oxidase 2 to mitochondrial oxidative stress in the kidneys of the Dahl salt-sensitive (SS) hypertensive rat. Whole kidney redox states were uniquely assessed using a custom-designed optical fluorescence three-dimensional cryoimager to acquire multichannel signals of the intrinsic fluorophores NADH and FAD. SS rats were compared with SS rats in which the cytosolic subunit p67(phox) was rendered functionally inactive by zinc finger nuclease mutation of the gene (SS(p67phox)-null rats). Kidneys of SS rats fed a 0.4% NaCl diet exhibited significantly (P = 0.023) lower tissue redox ratio (NADH/FAD; 1.42 ± 0.06, n = 5) than SS(p67phox)-null rats (1.64 ± 0.07, n = 5), indicating reduced levels of mitochondrial electron transport chain metabolic activity and enhanced oxidative stress in SS rats. When fed a 4.0% salt diet for 21 days, both strains exhibited significantly lower tissue redox ratios (P < 0.001; SS rats: 1.03 ± 0.05, n = 9, vs. SS(p67phox)-null rats: 1.46 ± 0.04, n = 7) than when fed a 0.4% salt, but the ratio was still significantly higher in SS(p67phox) rats at the same salt level as SS rats. These results are consistent with results from previous studies that found elevated medullary interstitial fluid concentrations of superoxide and H2O2 in the medulla of SS rats. We conclude that the p67(phox) subunit of NADPH oxidase 2 plays an important role in the excess production of ROS from mitochondria in the renal medulla of the SS rat.
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Affiliation(s)
- F Salehpour
- Biophotonics Lab, University of Wisconsin, Milwaukee, Wisconsin; and
| | - Z Ghanian
- Biophotonics Lab, University of Wisconsin, Milwaukee, Wisconsin; and
| | - C Yang
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - N N Zheleznova
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - T Kurth
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - R K Dash
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - A W Cowley
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - M Ranji
- Biophotonics Lab, University of Wisconsin, Milwaukee, Wisconsin; and
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Szeto HH, Liu S, Soong Y, Birk AV. Improving mitochondrial bioenergetics under ischemic conditions increases warm ischemia tolerance in the kidney. Am J Physiol Renal Physiol 2014; 308:F11-21. [PMID: 25339695 DOI: 10.1152/ajprenal.00366.2014] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Ischemia time during partial nephrectomy is strongly associated with acute and chronic renal injury. ATP depletion during warm ischemia inhibits ATP-dependent processes, resulting in cell swelling, cytoskeletal breakdown, and cell death. The duration of ischemia tolerated by the kidney depends on the amount of ATP that can be produced with residual substrates and oxygen in the tissue to sustain cell function. We previously reported that the rat can tolerate 30-min ischemia quite well but 45-min ischemia results in acute kidney injury and progressive interstitial fibrosis. Here, we report that pretreatment with SS-20 30 min before warm ischemia in the rat increased ischemia tolerance from 30 to 45 min. Histological examination of kidney tissues revealed that SS-20 reduced cytoskeletal breakdown and cell swelling after 45-min ischemia. Electron microscopy showed that SS-20 reduced mitochondrial matrix swelling and preserved cristae membranes, suggesting that SS-20 enhanced mitochondrial ATP synthesis under ischemic conditions. Studies with isolated kidney mitochondria showed dramatic reduction in state 3 respiration and respiratory control ratio after 45-min ischemia, and this was significantly improved by SS-20 treatment. These results suggest that SS-20 increases efficiency of the electron transport chain and improves coupling of oxidative phosphorylation. SS-20 treatment after ischemia also significantly reduced interstitial fibrosis. These new findings reveal that enhancing mitochondrial bioenergetics may be an important target for improving ischemia tolerance, and SS-20 may serve well for minimizing acute kidney injury and chronic kidney disease following surgical procedures such as partial nephrectomy and transplantation.
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Affiliation(s)
- Hazel H Szeto
- Research Program in Mitochondrial Therapeutics, Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, New York
| | - Shaoyi Liu
- Research Program in Mitochondrial Therapeutics, Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, New York
| | - Yi Soong
- Research Program in Mitochondrial Therapeutics, Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, New York
| | - Alexander V Birk
- Research Program in Mitochondrial Therapeutics, Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, New York
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Nourbakhsh N, Singh P. Role of renal oxygenation and mitochondrial function in the pathophysiology of acute kidney injury. Nephron Clin Pract 2014; 127:149-52. [PMID: 25343840 PMCID: PMC5540439 DOI: 10.1159/000363545] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
There are unique features of renal oxygenation that render the kidney susceptible to oxygen demand-supply mismatch and hypoxia. Renal oxygen consumption by oxidative metabolism is closely coupled to and driven by tubular transport, which is linked to the filtered solute load and glomerular filtration rate (GFR). In turn, filtered solute load and GFR are dependent on the renal blood flow. Hence, changes in renal blood flow increase oxygen delivery but also increase oxygen demand (consumption) simultaneously by increasing the tubular workload of solute transport. The renal blood flow to different regions of kidney is also inhomogeneous, increasing the oxygen demand-supply mismatch in particular areas such as the outer medulla which become more susceptible to injury. Thus, tubular transport and oxidative metabolism by mi ochondria are closely coupled in the kidney and are the principal determinants of intrarenal oxygenation. Here we review the published literature characterizing renal oxygenation and mitochondrial function in ischemic and sepsis-associated acute kidney injury (AKI). However, the coupling of transport and metabolism in AKI has not been examined. This is a potentially fruitful area of research that should become increasingly active given the emerging data linking renal oxygenation and hypoxia to acute and chronic dysfunction in the kidney.
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Affiliation(s)
- Noureddin Nourbakhsh
- Division of Nephrology-Hypertension, University of California San Diego School of Medicine, and VA San Diego Healthcare System, San Diego, Calif., USA
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Sahdeo S, Tomilov A, Komachi K, Iwahashi C, Datta S, Hughes O, Hagerman P, Cortopassi G. High-throughput screening of FDA-approved drugs using oxygen biosensor plates reveals secondary mitofunctional effects. Mitochondrion 2014; 17:116-25. [PMID: 25034306 DOI: 10.1016/j.mito.2014.07.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 06/11/2014] [Accepted: 07/01/2014] [Indexed: 10/25/2022]
Abstract
Repurposing of FDA-approved drugs with effects on mitochondrial function might shorten the critical path to mitochondrial disease drug development. We improved a biosensor-based assay of mitochondrial O2 consumption, and identified mitofunctional defects in cell models of LHON and FXTAS. Using this platform, we screened a 1600-compound library of clinically used drugs. The assay identified drugs known to affect mitochondrial function, such as metformin and decoquinate. We also identified several drugs not previously known to affect mitochondrial respiration including acarbose, metaraminol, gallamine triethiodide, and acamprosate. These previously unknown 'mitoactives' represent novel links to targets for mitochondrial regulation and potentially therapy, for mitochondrial disease.
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Affiliation(s)
- Sunil Sahdeo
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, 1089 Veterinary Medicine Drive, Davis, CA 95616, United States
| | - Alexey Tomilov
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, 1089 Veterinary Medicine Drive, Davis, CA 95616, United States
| | - Kelly Komachi
- Eon Research, 707 4th Street, Suite 305, Davis, CA 95616, United States
| | - Christine Iwahashi
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, 4455 Tupper Hall, Davis, CA 95616, United States
| | - Sandipan Datta
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, 1089 Veterinary Medicine Drive, Davis, CA 95616, United States
| | - Owen Hughes
- Eon Research, 707 4th Street, Suite 305, Davis, CA 95616, United States
| | - Paul Hagerman
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, 4455 Tupper Hall, Davis, CA 95616, United States
| | - Gino Cortopassi
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, 1089 Veterinary Medicine Drive, Davis, CA 95616, United States
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mTORC1 maintains renal tubular homeostasis and is essential in response to ischemic stress. Proc Natl Acad Sci U S A 2014; 111:E2817-26. [PMID: 24958889 DOI: 10.1073/pnas.1402352111] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Mammalian target of rapamycin complex 1 (mTORC1) is a key regulator of cell metabolism and autophagy. Despite widespread clinical use of mTORC1 inhibitors, the role of mTORC1 in renal tubular function and kidney homeostasis remains elusive. By using constitutive and inducible deletion of conditional Raptor alleles in renal tubular epithelial cells, we discovered that mTORC1 deficiency caused a marked concentrating defect, loss of tubular cells, and slowly progressive renal fibrosis. Transcriptional profiling revealed that mTORC1 maintains renal tubular homeostasis by controlling mitochondrial metabolism and biogenesis as well as transcellular transport processes involved in countercurrent multiplication and urine concentration. Although mTORC2 partially compensated for the loss of mTORC1, exposure to ischemia and reperfusion injury exaggerated the tubular damage in mTORC1-deficient mice and caused pronounced apoptosis, diminished proliferation rates, and delayed recovery. These findings identify mTORC1 as an important regulator of tubular energy metabolism and as a crucial component of ischemic stress responses.
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Ergin B, Kapucu A, Demirci-Tansel C, Ince C. The renal microcirculation in sepsis. Nephrol Dial Transplant 2014; 30:169-77. [PMID: 24848133 DOI: 10.1093/ndt/gfu105] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Despite identification of several cellular mechanisms being thought to underlie the development of septic acute kidney injury (AKI), the pathophysiology of the occurrence of AKI is still poorly understood. It is clear, however, that instead of a single mechanism being responsible for its aetiology, an orchestra of cellular mechanisms failing is associated with AKI. The integrative physiological compartment where these mechanisms come together and exert their integrative deleterious action is the renal microcirculation (MC). This is why it is opportune to review the response of the renal MC to sepsis and discuss the determinants of its (dys)function and how it contributes to the pathogenesis of renal failure. A main determinant of adequate organ function is the adequate supply and utilization of oxygen at the microcirculatory and cellular level to perform organ function. The highly complex architecture of the renal microvasculature, the need to meet a high energy demand and the fact that the kidney is borderline ischaemic makes the kidney a highly vulnerable organ to hypoxaemic injury. Under normal, steady-state conditions, oxygen (O2) supply to the renal tissues is well regulated; however, under septic conditions the delicate balance of oxygen supply versus demand is disturbed due to renal microvasculature dysfunction. This dysfunction is largely due to the interaction of renal oxygen handling, nitric oxide metabolism and radical formation. Renal tissue oxygenation is highly heterogeneous not only between the cortex and medulla but also within these renal compartments. Integrative evaluation of the different determinants of tissue oxygen in sepsis models has identified the deterioration of microcirculatory oxygenation as a key component in the development AKI. It is becoming clear that resuscitation of the failing kidney needs to integratively correct the homeostasis between oxygen, and reactive oxygen and nitrogen species. Several experimental therapeutic modalities have been found to be effective in restoring microcirculatory oxygenation in parallel to improving renal function following septic AKI. However, these have to be verified in clinical studies. The development of clinical physiological biomarkers of AKI specifically aimed at the MC should form a valuable contribution to monitoring such new therapeutic modalities.
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Affiliation(s)
- Bulent Ergin
- Department of Translational Physiology, Academic Medical Center, Amsterdam, The Netherlands
| | - Aysegul Kapucu
- Department of Translational Physiology, Academic Medical Center, Amsterdam, The Netherlands Department of Biology and Zoology Division, University of Istanbul, Istanbul, Turkey
| | - Cihan Demirci-Tansel
- Department of Biology and Zoology Division, University of Istanbul, Istanbul, Turkey
| | - Can Ince
- Department of Translational Physiology, Academic Medical Center, Amsterdam, The Netherlands
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Singh P, Ricksten SE, Bragadottir G, Redfors B, Nordquist L. Renal oxygenation and haemodynamics in acute kidney injury and chronic kidney disease. Clin Exp Pharmacol Physiol 2013; 40:138-47. [PMID: 23360244 DOI: 10.1111/1440-1681.12036] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 11/19/2012] [Accepted: 11/20/2012] [Indexed: 11/29/2022]
Abstract
Acute kidney injury (AKI) is a major burden on health systems and may arise from multiple initiating insults, including ischaemia-reperfusion injury, cardiovascular surgery, radiocontrast administration and sepsis. Similarly, the incidence and prevalence of chronic kidney disease (CKD) continues to increase, with significant morbidity and mortality. Moreover, an increasing number of AKI patients survive to develop CKD and end-stage renal disease. Although the mechanisms for the development of AKI and progression to CKD remain poorly understood, initial impairment of oxygen balance likely constitutes a common pathway, causing renal tissue hypoxia and ATP starvation that, in turn, induce extracellular matrix production, collagen deposition and fibrosis. Thus, possible future strategies for one or both conditions may involve dopamine, loop diuretics, atrial natriuretic peptide and inhibitors of inducible nitric oxide synthase, substances that target kidney oxygen consumption and regulators of renal oxygenation, such as nitric oxide and heme oxygenase-1.
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Affiliation(s)
- Prabhleen Singh
- Division of Nephrology-Hypertension, VA San Diego Healthcare System, University of California San Diego, San Diego, CA, USA
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Abstract
PURPOSE OF REVIEW To explore the causal relationship between metabolic syndrome, type 2 diabetes and hyperuricemia. RECENT FINDINGS The prevalence of hyperuricemia in male adults with metabolic syndrome was increased and a large difference in prevalence of metabolic syndrome also existed in those with hyperuricemia compared with normouricemia. Even in those with normouricemia, higher serum uric acid levels were associated with metabolic syndrome. Serum uric acid was an independent risk factor for incident diabetes, and evidence showed that the patients with both gout and type 2 diabetes exhibited a mutual inter-dependent effect on higher incidences. Furthermore, obese patients often demonstrated insulin resistance and adipose tissue macrophage with low-grade inflammation, which is suggested to be the major contributor. Although alcohol intake is considered a risk for developing hyperuricemia, moderate alcohol intake showed a lower risk for developing type 2 diabetes and insulin resistance. Hyperinsulinemia reduces renal excretion of uric acid on the proximal tubular of the kidney leading to hyperuricemia, which has deleterious effects on endothelial function and on nitric oxide bioavailability, thus causing hyperinsulinemia. SUMMARY We found evidence to suggest that insulin resistance plays a potentially key role in the causal relationship between metabolic syndrome, type 2 diabetes and hyperuricemia. Furthermore, it is likely that hyperuricemia and insulin resistance share a bidirectional causal effect.
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Silva GB, Atchison DK, Juncos LI, García NH. Anandamide inhibits transport-related oxygen consumption in the loop of Henle by activating CB1 receptors. Am J Physiol Renal Physiol 2012; 304:F376-81. [PMID: 23220721 DOI: 10.1152/ajprenal.00239.2012] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The energy required for active Na chloride reabsorption in the thick ascending limb (TAL) depends on oxygen consumption and oxidative phosphorylation (OXP). In other cells, Na transport is inhibited by the endogenous cannabinoid anandamide through the activation of the cannabinoid receptors (CB) type 1 and 2. However, it is unclear whether anandamide alters TAL transport and the mechanisms that could be involved. We hypothesized that anandamide inhibits TAL transport via activation of CB1 receptors and NO. For this, we measured oxygen consumption (Q(O(2))) in TAL suspensions to monitor the anandamide effects on transport and OXP. Anandamide reduced Q(O(2)) in a concentration-dependent manner. During Na-K-2Cl cotransport and Na/H exchange inhibition, anandamide did not inhibit TAL Q(O(2)). To test the role of the cannabinoid receptors, we used specific agonists and antagonists of CB1 and CB2 receptors. The CB1-selective agonist WIN55212-2 reduced Q(O(2)) in a concentration-dependent manner. Also, the CB1 receptor antagonist rimonabant blocked the effect of anandamide on Q(O(2)). In contrast, the CB2-selective agonist JHW-133 had no effect on Q(O(2)), while the CB2 receptor antagonist AM-630 failed to block the anandamide effects on Q(O(2)). To confirm these results, we measured CB1 and CB2 receptor expression and only CB1 expression was detected. Because CB1 receptors are strong nitric oxide synthase (NOS) stimulators and NO inhibits transport in TALs, we evaluated the role of NO. Anandamide stimulated NO production and the NOS inhibitor N(G)-nitro-L-arginine methyl ester blocked the anandamide effects on Q(O(2)). We conclude that anandamide inhibits TAL Na transport-related Q(O(2)) via activation of CB1 receptor and NOS.
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Affiliation(s)
- Guillermo B Silva
- School of Chemistry Science, Catholic Univ. of Córdoba, Consejo Nacional de Investigaciones Científicas y Técnicas, Córdoba, Argentina.
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Silva GB, Garvin JL. Extracellular ATP inhibits transport in medullary thick ascending limbs: role of P2X receptors. Am J Physiol Renal Physiol 2009; 297:F1168-73. [PMID: 19710240 DOI: 10.1152/ajprenal.00325.2009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Absorption of NaCl by the thick ascending limb (TAL) involves active transport and therefore depends on oxidative phosphorylation. Extracellular ATP has pleiotropic effects, including both stimulation and inhibition of transport and inhibition of oxidative phosphorylation. However, it is unclear whether ATP alters TAL transport and how this occurs. We hypothesized that ATP inhibits TAL Na absorption by reducing Na entry. We measured oxygen consumption in TAL suspensions. ATP reduced oxygen consumption in a concentration-dependent manner. The purinergic (P2) receptor antagonist suramin (300 microM) blocked the effect of ATP on TAL oxygen consumption (147 +/- 15 vs. 146 +/- 16 nmol O2 x min(-1) x mg protein(-1)). In contrast, the adenosine receptor antagonist theophylline did not block the effect of ATP on oxygen consumption. When Na-K-2Cl cotransport and Na/H exchange were blocked with furosemide (100 microM) plus dimethyl amiloride (100 microM), ATP did not inhibit TAL oxygen consumption (from 78 +/- 13 to 98 +/- 5 nmol O2 x min(-1) x mg protein(-1)). The Na ionophore nystatin (200 U/ml) increased TAL oxygen consumption to a similar extent in both ATP- and vehicle-treated samples (368 +/- 41 vs. 397 +/- 47 nmol O2 x min(-1) x mg protein(-1)). The nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (3 mM) blocked the ATP effects on TAL oxygen consumption (157 +/- 10 vs. 165 +/- 15 nmol O2 x min(-1) x mg protein(-1)). The P2X-selective receptor antagonist NF023 blocked the effect of ATP on oxygen consumption, whereas the P2X-selective agonist beta-gamma-Me-ATP reduced oxygen consumption in a concentration-dependent manner. We conclude that ATP inhibits Na transport-related oxygen consumption in TALs by reducing Na entry and P2X receptors and nitric oxide mediate this effect.
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Silva GB, Garvin JL. Angiotensin II-dependent hypertension increases Na transport-related oxygen consumption by the thick ascending limb. Hypertension 2008; 52:1091-8. [PMID: 19001187 DOI: 10.1161/hypertensionaha.108.120212] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Renal medullary superoxide (O(2)(-)) increases in angiotensin (Ang) II-dependent hypertension. O(2)(-) increases thick ascending limb Na transport, but the effect of Ang II-dependent hypertension on the thick ascending limb is unknown. We hypothesized that Ang II-dependent hypertension increases thick ascending limb NaCl transport because of enhanced O(2)(-) production and increased protein kinase C (PKC) alpha activity. We measured the effect of Ang II-dependent hypertension on furosemide-sensitive oxygen consumption (a measure of Na transport), O(2)(-) production, and PKCalpha translocation (a measure of PKCalpha activity) in thick ascending limb suspensions. Ang II-dependent hypertension increased furosemide-sensitive oxygen consumption (26.2+/-1.0% versus 36.6+/-1.2% of total oxygen consumption; P<0.01). O(2)(-) was also increased (1.1+/-0.2 versus 3.2+/-0.5 nmol of O(2)(-)/min per milligram of protein; P<0.03) in thick ascending limbs. Unilateral renal infusion of Tempol decreased O(2)(-) (2.4+/-0.4 versus 1.2+/-0.2 nmol of O(2)(-)/min per milligram of protein; P<0.04) and furosemide-sensitive oxygen consumption (32.8+/-1.3% versus 24.0+/-2.1% of total oxygen consumption; P<0.01) in hypertensive rats. Tempol did not affect O(2)(-) or furosemide-sensitive oxygen consumption in normotensive controls and did not alter systolic blood pressure. Ang II-dependent hypertension increased PKCalpha translocation (5.7+/-0.3 versus 13.8+/-1.4 AU per milligram of protein; P<0.01). Unilateral renal infusion of Tempol reduced PKCalpha translocation (5.0+/-0.9 versus 10.4+/-2.6 AU per milligram of protein; P<0.04) in hypertensive rats. Unilateral renal infusion of the PKCalpha inhibitor Gö6976 reduced furosemide-sensitive oxygen consumption (37.4+/-1.5% versus 25.1+/-1.0% of total oxygen consumption; P<0.01) in hypertensive rats. We conclude that Ang II-dependent hypertension enhances thick ascending limb Na transport-related oxygen consumption by increasing O(2)(-) and PKCalpha activity.
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Affiliation(s)
- Guillermo B Silva
- Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit, Michigan 48202, USA
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Lippi G, Montagnana M, Franchini M, Favaloro EJ, Targher G. The paradoxical relationship between serum uric acid and cardiovascular disease. Clin Chim Acta 2008; 392:1-7. [DOI: 10.1016/j.cca.2008.02.024] [Citation(s) in RCA: 160] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Revised: 02/25/2008] [Accepted: 02/29/2008] [Indexed: 02/07/2023]
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Abstract
A major challenge associated with the development of chemopreventive polyphenols is the lack of bioavailability in vivo, which are primarily the result of coupled metabolic activities of conjugating enzymes and efflux transporters. These coupling processes are present in disposition tissues and organs in mammals and are efficient for the purposes of drug metabolism, elimination and detoxification. Therefore, it was expected that these coupling processes represent a significant barrier to the oral bioavailabilities of polyphenols. In various studies of this coupling process, it was identified that various conjugating enzymes such as uridine 5'-diphosphate-glucuronosyltransferase and sulfotransferase are capable of producing very hydrophilic metabolites of polyphenols, which cannot diffuse out of the cells and needs the action of efflux transporters to pump them out of the cells. Additional studies have shown that efflux transporters, such as multi-drug resistance-associated protein 2, breast cancer-resistant protein and the organic anion transporters, appear to serve as the gate keeper when there is an excess capacity to metabolise the compounds. These efflux transporters may also act as the facilitator of metabolism when there is a product/metabolite inhibition. For polyphenols, these coupled processes enable a duo recycling scheme of enteric and enterohepatic recycling, which allows the polyphenols to be reabsorbed and results in longer than expected apparent plasma half-lifes for these compounds and their conjugates. Because the vast majority of polyphenols in plasma are hydrophilic conjugates, more research is needed to determine if the metabolites are active or reactive, which will help explain their mechanism of actions.
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Affiliation(s)
- Zhongqiu Liu
- Hong Kong Baptist University, School of Chinese Medicine, Hong Kong, China
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Tsouli SG, Liberopoulos EN, Mikhailidis DP, Athyros VG, Elisaf MS. Elevated serum uric acid levels in metabolic syndrome: an active component or an innocent bystander? Metabolism 2006; 55:1293-301. [PMID: 16979398 DOI: 10.1016/j.metabol.2006.05.013] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2005] [Accepted: 05/04/2006] [Indexed: 12/13/2022]
Abstract
Elevated serum uric acid (SUA) levels are commonly seen in patients with the metabolic syndrome (MetS). Several mechanisms, both direct and indirect, connect the increased SUA levels with the established diagnostic criteria of MetS. It is possible that the increased cardiovascular disease risk associated with the MetS is partially attributed to elevated circulating SUA concentration. Several drugs used in the treatment of MetS may alter SUA levels. Thus, lifestyle measures together with the judicious selection of drugs for the treatment of hypertension, dyslipidemia, and insulin resistance associated with MetS may result in a reduction of SUA levels and possibly cardiovascular disease risk. This review summarizes the pathophysiologic association between SUA and MetS and focuses on the prevention of hyperuricemia and its cardiovascular consequences.
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Affiliation(s)
- Sofia G Tsouli
- Department of Internal Medicine, School of Medicine, University of Ioannina, 45110 Ioannina, Greece
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Handa RK, Strandhoy JW, Giammattei CE, Handa SE. Platelet-activating factor and solute transport processes in the kidney. Am J Physiol Renal Physiol 2003; 284:F274-81. [PMID: 12529272 DOI: 10.1152/ajprenal.00117.2002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined the hemodynamic and tubular transport mechanisms by which platelet-activating factor (PAF) regulates salt and water excretion. In anesthetized, renally denervated male Wistar rats, with raised systemic blood pressure and renal arterial blood pressure maintained at normal levels, intrarenal PAF infusion at 2.5 ng. min(-1) x kg(-1) resulted in a small fall in systemic blood pressure (no change in renal arterial blood pressure) and an increase in renal blood flow and urinary water, sodium, and potassium excretion rates. The PAF-induced changes in cardiovascular and renal hemodynamic function were abolished and renal excretory function greatly attenuated by treating rats with a nitric oxide synthase inhibitor. To determine whether a tubular site of action was involved in the natriuretic effect of PAF, cortical proximal tubules were enzymatically dissociated from male Wistar rat kidneys, and oxygen consumption rates (Qo(2)) were used as an integrated index of transcellular sodium transport. PAF at 1 nM maximally inhibited Qo(2) in both untreated and nystatin-stimulated (sodium entry into renal cell is not rate limiting) proximal tubules by approximately 20%. Blockade of PAF receptors or Na(+)-K(+)-ATPase pump activity with BN-52021 or ouabain, respectively, abolished the effect of PAF on nystatin-stimulated proximal tubule Qo(2). Inhibition of nitric oxide synthase or guanylate cyclase systems did not alter PAF-mediated inhibition of nystatin-stimulated proximal tubule Qo(2), whereas phospholipase A(2) or cytochrome-P-450 monooxygenase inhibition resulted in a 40-60% reduction. These findings suggest that stimulation of PAF receptors on the proximal tubule decreases transcellular sodium transport by activating phospholipase A(2) and the cytochrome-P-450 monooxygenase pathways that lead to the inhibition of an ouabain-sensitive component of the basolateral Na(+)-K(+)-ATPase pump. Thus PAF can activate both an arachidonate pathway-mediated suppression of proximal tubule sodium transport and a nitric oxide pathway-mediated dilatory action on renal hemodynamics that likely contributes to the natriuresis and diuresis observed in vivo.
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Affiliation(s)
- Rajash K Handa
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
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Clarson LH, Greenwood SL, Mylona P, Sibley CP. Inwardly rectifying K(+) current and differentiation of human placental cytotrophoblast cells in culture. Placenta 2001; 22:328-36. [PMID: 11286569 DOI: 10.1053/plac.2000.0622] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Ion transport is important for driving nutrient transport across the syncytiotrophoblast and yet is poorly understood. We have examined K(+)currents under basal conditions in cultured cytotrophoblast cells, at various stages of differentiation, using the whole cell patch clamp technique. Cytotrophoblast cells were isolated from human term placenta and maintained in culture for up to 3 days. Cells were studied at four stages of progressive morphological differentiation: (i) mononuclear cells, (ii) mononuclear cells in aggregates, (iii) small multinucleate cells and (iv) large multinucleate syncytiotrophoblast-like cells. In the conditions of whole cell recording the only K(+) selective current identified in all cell types was a strong inwardly rectifying current which was sensitive to Ba(2+) and Cs(+). This current was unaffected by intracellular ATP whereas intracellular GTPgammas caused either run down of the current or activated a linear current. The characteristics of the current described are consistent with those of the inwardly rectifying K(+) channel Kir2.1. The inwardly rectifying K(+) current was observed in three out of 19 (16 per cent ) mononuclear cells, seven out of 21 (33 per cent ) mononuclear aggregates, eight out of 21 (38 per cent ) small multinucleate cells and 16 out of 19 (84 per cent ) large multinucleate cells. This inwardly rectifying K(+) current is likely to have an important role in determining net K(+) diffusion across the syncytiotrophoblast cell membrane, perhaps increasing in importance as the cells terminally differentiate.
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Affiliation(s)
- L H Clarson
- Academic Unit of Child Health, University of Manchester, St. Mary's Hospital, Manchester, UK.
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40
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Handa RK. Angiotensin-(1-7) can interact with the rat proximal tubule AT(4) receptor system. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:F75-83. [PMID: 10409300 DOI: 10.1152/ajprenal.1999.277.1.f75] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study was undertaken to identify the non-AT(1), non-AT(2) angiotensin receptor that mediates the ANG-(1-7) inhibitory action on rat proximal tubule transport processes. ANG-(1-7) inhibited nystatin-stimulated, ouabain-suppressible O(2) consumption (QO(2)) rates in freshly isolated rat proximal tubules (reflecting reduced basolateral Na(+)-K(+)-ATPase activity). Selective angiotensin-receptor subtype antagonists revealed that AT(1) and AT(4) receptors mediated the response of ANG-(1-7). Receptor autoradiography of the rat kidney demonstrated a high density of AT(1) and AT(4) receptors and no specific (125)I-ANG(1-7) binding sites. Competition assays in rat kidney sections indicated that ANG-(1-7) competed predominantly for the AT(1) receptor site, whereas its NH(2)-terminal-deleted metabolite, ANG-(3-7), competed primarily for the AT(4)-receptor site. Metabolism of (125)I-ANG-(1-7) in rat proximal tubules generated peptide fragments that included ANG-(3-7), with the pentapeptide producing a concentration-dependent inhibition of nystatin-stimulated proximal tubule QO(2) that was abolished by AT(4)-receptor blockade. These results suggest that the generation of ANG-(3-7) from the NH(2)-terminal metabolism of ANG-(1-7) caused the interaction of the parent peptide with the proximal tubule AT(4) receptor, which elicited a decrease in energy-dependent solute transport.
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Affiliation(s)
- R K Handa
- Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, College of Veterinary Medicine, Washington State University, Pullman, Washington 99164-6520, USA
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Portier F, van den Abbeele T, Lecain E, Sauvaget E, Escoubet B, Huy PT, Herman P. Oxygen modulates Na+ absorption in middle ear epithelium. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:C312-7. [PMID: 9950758 DOI: 10.1152/ajpcell.1999.276.2.c312] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The physiology of the middle ear is primarily concerned with keeping the cavities air filled and fluid free to allow transmission of the sound vibrations from the eardrum to the inner ear. Middle ear epithelial cells are thought to play a key role in this process, since they actively transport Na+ and water. The PO2 of the middle ear cavities varies from 44 to 54 mmHg in healthy human ears but may be lower in the course of secretory otitis media. The effect of chronic hypoxia on ion transport was investigated on a middle ear cell line using the short-circuit current technique. Chronic hypoxia reversibly decreased the rate of Na+ absorption across the MESV cell line. Although a decrease in cellular ATP content was observed, the decrease of Na+ absorption seemed related to a primary modulation of apical Na+ entry. As revealed by RNase protection assay, the decrease in the rate of apical Na+ entry strictly paralleled the decrease in the expression of transcripts encoding the alpha-subunit of the epithelial Na+ channel. This effect of oxygen on Na+ absorption might account for 1) the presence of fluid in the middle ear in the course of secretory otitis media and 2) the beneficial effect of the ventilation tube in treating otitis media that allows the PO2 to rise and restores the fluid clearance.
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Affiliation(s)
- F Portier
- Laboratoire d'Otologie Expérimentale, Faculté Lariboisière-St-Louis, Institut National de la Santé et de la Recherche Médicale Unité 426, Faculté Xavier Bichat, Université Paris VII, 75010 Paris, France
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Abstract
There is concern that environmental and dietary aluminum (Al) might cause developmental toxicity. To better understand this concern, we reviewed published studies which administered Al compounds to pregnant animals and measured accumulation of Al in mother, fetus, or born offspring. A total of 7 studies were identified which administered Al during gestation and evaluated fetal accumulation. Another 7 studies administered Al at least until birth and then evaluated accumulation in mothers and/or pups. These 14 studies included 4 different Al compounds (hydroxide, chloride, lactate, and citrate) administered by 4 different routes (gavage, feed, intraperitoneal injection, and subcutaneous injection) with total doses ranging from 13.5 to 8,400 mg/kg. Fetal Al levels were not increased in 6 of 7 studies and pup Al levels were not increased in 4 of 5 studies in which they were measured. Maternal Al levels were increased in some studies, but there was no consistent pattern of organ-specific accumulation and several positive studies were contradicted by subsequent reports from the same laboratory. Placental levels were increased in 6 of 9 studies and were greater than corresponding fetal levels. The weight of evidence in these studies suggests that environmental and dietary Al exposures are unlikely to pose risks of Al accumulation to pregnant animals or their fetuses.
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Affiliation(s)
- J Borak
- Department of Internal Medicine, Yale University, New Haven, Connecticut 06510, USA.
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Handa RK, Krebs LT, Harding JW, Handa SE. Angiotensin IV AT4-receptor system in the rat kidney. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:F290-9. [PMID: 9486224 DOI: 10.1152/ajprenal.1998.274.2.f290] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Angiotensin IV, [[des-Asp1,Arg2]ANG II or ANG-(3-8)], has been shown to preferentially bind to a novel angiotensin binding site (AT4 receptor). The cellular location and function of this receptor in the rat kidney is unknown. Autoradiography localized AT4 receptors to the cell body and apical membrane of convoluted and straight proximal tubules in the cortex and outer stripe of the outer medulla. ANG IV (0.1 pM-1 microM) elicited a concentration-dependent decrease in transcellular Na+ transport (as measured by proximal tubule O2 consumption rates) in fresh suspensions of control or nystatin-stimulated (bypasses rate-limiting step of apical Na+ entry) rat proximal tubules. The inhibitory effect of 1 pM ANG IV was unaltered by either 1 microM losartan (AT1-receptor antagonist) or 1 microM PD-123319 (AT2-receptor antagonist) and yet was abolished by 1 microM divalinal-ANG IV (AT4-receptor antagonist) or ouabain pretreatment. These results demonstrate that the kidney AT4-receptor system is localized to the proximal tubule and suggests that one potential biological role of this system is in the regulation of Na+ transport by inhibiting a ouabain-sensitive component of Na(+)-K(+)-adenosinetriphosphatase activity in the rat.
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Affiliation(s)
- R K Handa
- Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, College of Veterinary Medicine, Washington State University, Pullman 99164, USA
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Birdsey TJ, Boyd RD, Sibley CP, Greenwood SL. Microvillous membrane potential (Em) in villi from first trimester human placenta: comparison to Em at term. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 273:R1519-28. [PMID: 9362319 DOI: 10.1152/ajpregu.1997.273.4.r1519] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The microvillous membrane (MVM) potential (Em) of first trimester human placental villi was measured and compared with that in villi from term human placentas. The median Em in first trimester villi (-28 mV) was significantly more negative than that at term (-21 mV; P < 0.001). The median Em measured in villi from early (weeks 6-11) first trimester (-32 mV) was significantly more negative than that in late (weeks 12 and 13) first trimester villi (-24 mV; P < 0.001). Elevating extracellular KCl concentration induced a significant depolarization of Em in both first trimester and term villi (P < 0.05 and P < 0.001, respectively). The magnitude of this depolarization was greater in first trimester than at term, indicating that the ion conductance of the MVM changes with gestation. Exposure to ouabain induced a significant depolarization of Em (3 mV: P < 0.05) in first trimester villi but had little effect at term. These results suggest that microvillous membrane electrophysiology changes with placental development. An alteration in the relative K+:Cl- conductance of the MVM is likely to be a major contributor to the change in the magnitude of Em.
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Affiliation(s)
- T J Birdsey
- Department of Child Health and School of Biological Sciences, University of Manchester, St. Mary's Hospital, United Kingdom
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Heemskerk AE, Huisman E, van Lambalgen AA, van den Bos GC, Hennekes MW, Thijs LG, Tangelder GJ. Influence of fluid resuscitation on renal function in bacteremic and endotoxemic rats. J Crit Care 1997; 12:120-31. [PMID: 9328851 DOI: 10.1016/s0883-9441(97)90041-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
PURPOSE Fluid resuscitation, which is the most important primary therapy in sepsis, is not always able to prevent acute renal failure. In this study, we investigated in two different rat models of distributive shock whether fluid resuscitation would increase renal plasma flow (RPF) and subsequently glomerular filtration rate (GFR). MATERIALS AND METHODS In pentobarbital anesthetized wistar rats Haemaccel (Behring Pharma, Hoechst, the Netherlands) infusion (1.2 mL/100 g/h for 3 hours) was started immediately during either bacteremia (bolus of living Escherichia coli bacteria, 10(9) or endotoxemia (1 hour infusion of E. coli endotoxin, 8 mg/kg), as well as in time-matched healthy controls. RESULTS After 3 hours, this treatment had increased RPF (clearance of 131I-hippurate) above normal in control (+67%) and bacteremic rats (+75%), whereas in endotoxemic animals, the significantly decreased RPF was normalized. On the other hand, in bacteremic animals, the lowered GFR (clearance of creatinine; x44%) was normalized, whereas in endotoxemic animals GFR remained depressed (x30%). The lack of improvement in GFR during endotoxemia was also indicated by a profound fall in urine flow, which by contrast steadily increased in control and bacteremic rats owing to volume loading. In both shocked groups, the decreased renal oxygen delivery was normalized, but the higher renal oxygen consumption than expected on the basis of the work needed for sodium reabsorption was not influenced by Haemaccel treatment, despite the fact that it caused this work load to rise in bacteremic but not in endotoxemic rats. In both shock models, renal cortical adenosine triphosphate content did not differ from healthy controls and was not influenced by volume loading. CONCLUSIONS In conclusion, our study suggests that a decrease in GFR caused by live bacteria in the circulation may benefit from fluid resuscitation, while during endotoxemia this therapy could not prevent acute renal failure.
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Affiliation(s)
- A E Heemskerk
- Laboratory for Physiology, Vrije Universiteit, Amsterdam, The Netherlands
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Huang RN, Lee TC. Arsenite efflux is inhibited by verapamil, cyclosporin A, and GSH-depletingagents in arsenite-resistant chinese hamster ovary cells. Toxicol Appl Pharmacol 1996. [DOI: 10.1016/s0041-008x(96)80004-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Nonaka T, Warden DH, Matsushita K, Stokes JB. K+ self-exchange by the Na+ pump: regulation by P(i) and metabolic perturbations. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 269:C170-8. [PMID: 7631743 DOI: 10.1152/ajpcell.1995.269.1.c170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We have previously demonstrated that the Na(+)-K+ pump on the basolateral membrane of the rabbit cortical collecting duct can function in the K+/K+ exchange mode. Increasing intracellular phosphate in red blood cells inhibits the Na+ pump and increases K+/K+ exchange. We found that maneuvers designed to increase intracellular phosphate in collecting duct cells caused an increase in K+/K+ exchange. Subjecting the cells to a metabolic insult (cyanide) increased K+/K+ exchange by the pump as judged by its ouabain sensitivity and lack of electrogenic or conductive characteristics. The results demonstrate that the rate of K+/K+ exchange by the Na(+)-K+ pump can be altered by changes in intracellular phosphate over a range that is physiologically or pathologically achievable. The results also suggest a mechanism for inhibition of vectorial Na+ transport during metabolic stress.
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Affiliation(s)
- T Nonaka
- Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, USA
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Nonaka T, Stokes JB. Metabolic support of Na+ transport by the rabbit CCD: analysis of the use of equivalent current. Kidney Int 1994; 45:743-52. [PMID: 8196275 DOI: 10.1038/ki.1994.99] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The role of metabolism in the support of ion transport by the cortical collecting duct (CCD) is being increasingly recognized as a complex process involving energy supply to the Na+/K+ pump and maintenance of cellular conductive pathways. In order to assess both of these processes, we measured the metabolic support of Na+ transport using transepithelial electrical measurements and, in some cases, simultaneous determination of lumen-to-bath Na+ flux. Analysis of the calculated equivalent current (Ieq), the product of the transepithelial voltage and conductance, showed a predicted (and a measured) discrepancy between this value and the magnitude of active Na+ transport. Under conditions of this study, the change in Ieq in a single tubule was a reasonable index of the change in Na+ transport. The majority of the support of Na+ transport appears to come from oxidative metabolism. Glucose supports transport better than the other substrates tested, but lactate, pyruvate, and some acids provide near maximal support. We found some conditions where large changes in Na+ transport occurred without significant changes in conductance. Conductance could also be altered without producing major changes in transport. These results demonstrate complex and possibly independent influences of metabolism in the regulation of Na+ transport and cell conductive pathways.
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Affiliation(s)
- T Nonaka
- Department of Internal Medicine, University of Iowa College of Medicine, Iowa City
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Djouadi F, Bastin J, Wijkhuisen A, Vilar J, Merlet-Bénichou C. Lack of control by adrenal steroids of oxidative enzymes and Na/K-ATPase development in the rat proximal tubule. Pflugers Arch 1993; 424:165-70. [PMID: 8414904 DOI: 10.1007/bf00374608] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The activities of citrate synthase, 3-oxoacid CoA-transferase, and Na/K-ATPase were determined in the proximal convoluted tubules (PCT) of midcortical nephrons from 16-, 21- and 30-day-old and adult rats. Enzyme microassays based on NAD amplification were run on tubule segments microdissected from lyophilized tissue sections, and the activities were expressed per unit of tissue dry weight. The activities of 3-oxoacid CoA-transferase (+ 155%) and citrate synthase (+ 44%) increased between 16 and 30 days, while no significant change in Na/K-ATPase activity occurred during this period. The results obtained in PCT from subcapsular nephrons were similar. It is concluded that active transport of Na+ coupled to mitochondrial ATP production might be mature in the PCT by the time of weaning, consistent with data on the development of Na+ reabsorption. Since adrenalectomy on day 16 induced no changes in the activities of oxidative enzymes or Na/K-ATPase on day 21 in midcortical or subcapsular PCT, the physiological rise in circulating glucocorticoids, characteristic of the weaning period, does not trigger the development of oxidative enzymes and Na/K-ATPase in the PCT of the developing rat kidney.
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Affiliation(s)
- F Djouadi
- Inserm U.319, Université Paris, France
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Renton KA, Manchester KL, Kilroe-Smith TA. The transport of aluminum and water across the rat small intestine. J Inorg Biochem 1993; 50:21-9. [PMID: 8473881 DOI: 10.1016/0162-0134(93)80011-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Aluminum transport across the epithelium of the rat small intestine has been investigated to determine factors affecting its absorption and its effect on the transport of other substances across the membrane. The intestines were attached to a perfusion apparatus and perfused with Krebs-Ringer-bicarbonate buffer containing aluminum. The transport of aluminum and buffer ions across the small intestine were measured. Phosphate transport was found to be the most satisfactory marker for viability. It is impossible to accurately measure the aluminum transport across a biological membrane unless the aluminum concentration of the solution is stable over the period of measurement. Hence, the solutions were stabilized with citrate ions which made them stable over a period of at least two hours. The velocity of transport of aluminum across the epithelium increased steadily and only became constant after about one hour. The steady state value of 0.12 micrograms atom of Al/hr/mg dry tissue compares well with that reported in the literature for stable aluminum solutions. Aluminum inhibited the transport of water across the membrane, but the inhibition took about two hours to reach a steady state of about 50% of the control value. This indicates that aluminum-containing medications and foods are able to interfere with the absorption of nutrients from the gut. Aluminum salts may therefore be useful to prevent rapid dehydration in the treatment of certain diseases such as cholera.
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Affiliation(s)
- K A Renton
- National Centre for Occupational Health, Johannesburg, South Africa
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