1
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Pham TD, Verlander JW, Chen C, Pech V, Kim HI, Kim YH, Weiner ID, Milne GL, Zent R, Bock F, Brown D, Eaton A, Wall SM. Angiotensin II acts through Rac1 to upregulate pendrin: role of NADPH oxidase. Am J Physiol Renal Physiol 2024; 326:F202-F218. [PMID: 38059296 PMCID: PMC11198991 DOI: 10.1152/ajprenal.00139.2023] [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: 05/22/2023] [Revised: 11/14/2023] [Accepted: 11/14/2023] [Indexed: 12/08/2023] Open
Abstract
Angiotensin II increases apical plasma membrane pendrin abundance and function. This study explored the role of the small GTPase Rac1 in the regulation of pendrin by angiotensin II. To do this, we generated intercalated cell (IC) Rac1 knockout mice and observed that IC Rac1 gene ablation reduced the relative abundance of pendrin in the apical region of intercalated cells in angiotensin II-treated mice but not vehicle-treated mice. Similarly, the Rac1 inhibitor EHT 1864 reduced apical pendrin abundance in angiotensin II-treated mice, through a mechanism that does not require aldosterone. This IC angiotensin II-Rac1 signaling cascade modulates pendrin subcellular distribution without significantly changing actin organization. However, NADPH oxidase inhibition with APX 115 reduced apical pendrin abundance in vivo in angiotensin II-treated mice. Moreover, superoxide dismutase mimetics reduced Cl- absorption in angiotensin II-treated cortical collecting ducts perfused in vitro. Since Rac1 is an NADPH subunit, Rac1 may modulate pendrin through NADPH oxidase-mediated reactive oxygen species production. Because pendrin gene ablation blunts the pressor response to angiotensin II, we asked if pendrin blunts the angiotensin II-induced increase in kidney superoxide. Although kidney superoxide was similar in vehicle-treated wild-type and pendrin knockout mice, it was lower in angiotensin II-treated pendrin-null kidneys than in wild-type kidneys. We conclude that angiotensin II acts through Rac1, independently of aldosterone, to increase apical pendrin abundance. Rac1 may stimulate pendrin, at least partly, through NADPH oxidase. This increase in pendrin abundance contributes to the increment in blood pressure and kidney superoxide content seen in angiotensin II-treated mice.NEW & NOTEWORTHY This study defines a new signaling mechanism by which angiotensin II modulates oxidative stress and blood pressure.
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Affiliation(s)
- Truyen D Pham
- Renal Division, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, The University of Florida College of Medicine, Gainesville, Florida, United States
| | - Chao Chen
- Division of Nephrology, Hypertension and Renal Transplantation, The University of Florida College of Medicine, Gainesville, Florida, United States
| | - Vladimir Pech
- Renal Division, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Hailey I Kim
- Renal Division, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Young Hee Kim
- Renal Division, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States
| | - I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, The University of Florida College of Medicine, Gainesville, Florida, United States
- Nephrology and Hypertension Section, Gainesville Veterans Affairs Medical Center, Gainesville, Florida, United States
| | - Ginger L Milne
- Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States
| | - Roy Zent
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
- Department of Veterans Affairs Hospital, Nashville, Tennessee, United States
| | - Fabian Bock
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
- Department of Veterans Affairs Hospital, Nashville, Tennessee, United States
| | - Dennis Brown
- Program in Membrane Biology, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States
| | - Amity Eaton
- Program in Membrane Biology, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States
| | - Susan M Wall
- Renal Division, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States
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2
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Muñoz M, López-Oliva ME, Rodríguez C, Martínez MP, Sáenz-Medina J, Sánchez A, Climent B, Benedito S, García-Sacristán A, Rivera L, Hernández M, Prieto D. Differential contribution of Nox1, Nox2 and Nox4 to kidney vascular oxidative stress and endothelial dysfunction in obesity. Redox Biol 2019; 28:101330. [PMID: 31563085 PMCID: PMC6812001 DOI: 10.1016/j.redox.2019.101330] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 08/27/2019] [Accepted: 09/16/2019] [Indexed: 01/16/2023] Open
Abstract
Oxidative stress-associated endothelial dysfunction is a key pathogenic factor underlying the microvascular complications of metabolic disease. NADPH oxidase (Nox) is a major source of oxidative stress in diabetic nephropathy and chronic kidney disease, despite Nox4 and Nox2 have been identified as relevant sources of vasodilator endothelial H2O2.The present study was sought to investigate the role of Nox enzymes in renal vascular oxidative stress and endothelial dysfunction in a rat model of genetic obesity. Endothelial function was assessed in intrarenal arteries of obese Zucker rats (OZR) and their counterparts lean Zucker rats (LZR) mounted in microvascular myographs, and superoxide (O2.-) and H2O2 production were measured. Impaired endothelium-dependent relaxations to acetylcholine (ACh) were associated to augmented O2.- generation, but neither ROS scavengers nor the Nox inhibitor apocynin significantly improved these relaxant responses in renal arteries of OZR. Whereas NO contribution to endothelial relaxations was blunted, catalase-sensitive non-NO non-prostanoid relaxations were enhanced in obese rats. Interestingly, NADPH-dependent O2.- production was augmented while NADPH-dependent H2O2 generation was reduced, and cytosolic and mitochondrial SOD were up-regulated in kidney of obese rats. Nox4 was down-regulated in renal arteries and Nox4-dependent H2O2 generation and endothelial relaxation were reduced in OZR. Up-regulation of both Nox2 and Nox1 was associated with augmented O2.- production but reduced H2O2 generation and blunted endothelial Nox2-derived H2O2-mediated in obese rats. Moreover, increased Nox1-derived O2.- contributed to renal endothelial dysfunction in OZR. In summary, the current data support a main role for Nox1-derived O2.- in kidney vascular oxidative stress and renal endothelial dysfunction in obesity, while reduced endothelial Nox4 expression associated to decreased H2O2 generation and H2O2-mediated vasodilatation might hinder Nox4 protective renal effects thus contributing to kidney injury. This suggests that effective therapies to counteract oxidative stress and prevent microvascular complications must identify the specific Nox subunits involved in metabolic disease.
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Affiliation(s)
- Mercedes Muñoz
- Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
| | | | - Claudia Rodríguez
- Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
| | - María Pilar Martínez
- Departamento de Anatomía y Embriología, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain
| | - Javier Sáenz-Medina
- Departamento de Urología, Hospital Universitario Puerta de Hierro-Majadahonda, Madrid, Spain
| | - Ana Sánchez
- Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
| | - Belén Climent
- Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
| | - Sara Benedito
- Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
| | | | - Luis Rivera
- Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
| | - Medardo Hernández
- Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain
| | - Dolores Prieto
- Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain.
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3
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Kamel KS, Schreiber M, Halperin ML. Renal potassium physiology: integration of the renal response to dietary potassium depletion. Kidney Int 2018; 93:41-53. [PMID: 29102372 DOI: 10.1016/j.kint.2017.08.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 07/31/2017] [Accepted: 08/03/2017] [Indexed: 01/30/2023]
Abstract
We summarize the current understanding of the physiology of the renal handling of potassium (K+), and present an integrative view of the renal response to K+ depletion caused by dietary K+ restriction. This renal response involves contributions from different nephron segments, and aims to diminish the rate of excretion of K+ as a result of: decreasing the rate of electrogenic (and increasing the rate of electroneutral) reabsorption of sodium in the aldosterone-sensitive distal nephron (ASDN), decreasing the abundance of renal outer medullary K+ channels in the luminal membrane of principal cells in the ASDN, decreasing the flow rate in the ASDN, and increasing the reabsorption of K+ in the cortical and medullary collecting ducts. The implications of this physiology for the association between K+ depletion and hypertension, and K+ depletion and formation of calcium kidney stones are discussed.
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Affiliation(s)
- Kamel S Kamel
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada; Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
| | - Martin Schreiber
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Mitchell L Halperin
- Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada; Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
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4
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Wheatley W, Kohan DE. Role for reactive oxygen species in flow-stimulated inner medullary collecting duct endothelin-1 production. Am J Physiol Renal Physiol 2017; 313:F514-F521. [PMID: 28515175 DOI: 10.1152/ajprenal.00103.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 05/08/2017] [Accepted: 05/13/2017] [Indexed: 12/22/2022] Open
Abstract
Inner medullary collecting duct (IMCD)-derived endothelin-1 (ET-1) is stimulated by volume expansion, in part through augmented luminal flow, whereupon it can elicit natriuresis and diuresis. Since flow can alter nitric oxide (NO) and reactive oxygen species (ROS), both of which can affect collecting duct salt transport, we asked whether NO and/or ROS mediate flow-stimulated IMCD ET-1. Mouse IMCD3 cells were exposed to flow, and ET-1/GAPDH mRNA was assessed. A shear stress of 10 dyn/cm2 for 1 h increased ET-1 mRNA by fourfold compared with no flow (ET-1 flow response). Global NO synthase (NOS) inhibition [NG-nitro-l-arginine methyl ester (l-NAME)] reduced the ET-1 flow response; however, pharmacological inhibition of NOS1 or NOS2, inhibition of NOS3 siRNA, inhibition of arginase inhibition, removal of media l-Arg, or inhibition of NO-dependent signaling pathways (PKG, guanylyl cyclase, or NF-κB) did not affect the ET-1 flow response. Tempol reduced the ET-1 flow response; no further inhibition occurred with l-NAME. Superoxide dismutase, but not catalase, reduced the ET-1 flow response. Inhibition of NAPDH oxidase (NOX) (apocynin), pharmacological inhibition of NOX1/4, or NOX4 siRNA reduced the ET-1 flow response. Finally, flow increased IMCD3 ROS production and this was inhibited by apocynin, NOX1/4 inhibition, and, to a small extent, by l-NAME. Taken together, these data suggest that NOX4-derived ROS in general, and possibly superoxide in particular, are involved in flow-stimulated IMCD ET-1 production. To our knowledge, this is the first report of flow-stimulated ROS production by the CD, as well as the first report of such flow-stimulated CD ROS exerting a biological effect.
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Affiliation(s)
- Will Wheatley
- Division of Nephrology, University of Utah Health Sciences Center, Salt Lake City, Utah; and
| | - Donald E Kohan
- Division of Nephrology, University of Utah Health Sciences Center, Salt Lake City, Utah; and .,George E. Wahlen Department of Veterans Affairs Medical Center, Salt Lake City, Utah
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5
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Wang L, Zhang C, Su XT, Lin DH, Wu P, Schwartzman ML, Wang WH. PGF 2α regulates the basolateral K channels in the distal convoluted tubule. Am J Physiol Renal Physiol 2017; 313:F254-F261. [PMID: 28356287 PMCID: PMC5582901 DOI: 10.1152/ajprenal.00102.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 03/17/2017] [Accepted: 03/23/2017] [Indexed: 11/22/2022] Open
Abstract
Our aim is to examine the role of PGF2α receptor (FP), a highly expressed prostaglandin receptor in the distal convoluted tubule (DCT) in regulating the basolateral 40-pS K channel. The single-channel studies demonstrated that PGF2α had a biphasic effect on the 40-pS K channel in the DCT-PGF2α stimulated at low concentrations (less than 500 nM), while at high concentrations (above 1 µM), it inhibited the 40-pS K channels. Moreover, neither 13,14-dihydro-15-keto-PGF2α (a metabolite of PGF2α) nor PGE2 was able to mimic the effect of PGF2α on the 40-pS K channel in the DCT. The inhibition of PKC had no significant effect on the 40-pS K channel; however, it abrogated the inhibitory effect of 5 µM PGF2α on the K channel. Moreover, stimulation of PKC inhibited the 40-pS K channel in the DCT, suggesting that PKC mediates the inhibitory effect of PGF2α on the 40-pS K channel. Conversely, the stimulatory effect of PGF2α on the 40-pS K channel was absent in the DCT treated with DPI, a NADPH oxidase (NOX) inhibitor. Also, adding 100 µM H2O2 mimicked the stimulatory effect of PGF2α and increased the 40-pS K channel activity in DCT. Moreover, the stimulatory effect of 500 nM PGF2α and H2O2 was not additive, suggesting the role of superoxide-related species in mediating the stimulatory effect of PGF2α on the 40-pS K channel. The inhibition of Src family tyrosine protein kinase (SFK) not only inhibited the 40-pS K channel in the DCT but also completely abolished the stimulatory effects of PGF2α and H2O2 on the 40-pS K channel. We conclude that PGF2α at low doses stimulates the basolateral 40-pS K channel by a NOX- and SFK-dependent mechanism, while at high concentrations, it inhibits the K channel by a PKC-dependent pathway.
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Affiliation(s)
- Lijun Wang
- Department of Physiology, Harbin Medical University, Harbin, China; and.,Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Chengbiao Zhang
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Xiao-Tong Su
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Dao-Hong Lin
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Peng Wu
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | | | - Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York
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6
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Gonzalez-Vicente A, Garvin JL. Effects of Reactive Oxygen Species on Tubular Transport along the Nephron. Antioxidants (Basel) 2017; 6:antiox6020023. [PMID: 28333068 PMCID: PMC5488003 DOI: 10.3390/antiox6020023] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 03/15/2017] [Accepted: 03/18/2017] [Indexed: 12/17/2022] Open
Abstract
Reactive oxygen species (ROS) are oxygen-containing molecules naturally occurring in both inorganic and biological chemical systems. Due to their high reactivity and potentially damaging effects to biomolecules, cells express a battery of enzymes to rapidly metabolize them to innocuous intermediaries. Initially, ROS were considered by biologists as dangerous byproducts of respiration capable of causing oxidative stress, a condition in which overproduction of ROS leads to a reduction in protective molecules and enzymes and consequent damage to lipids, proteins, and DNA. In fact, ROS are used by immune systems to kill virus and bacteria, causing inflammation and local tissue damage. Today, we know that the functions of ROS are not so limited, and that they also act as signaling molecules mediating processes as diverse as gene expression, mechanosensation, and epithelial transport. In the kidney, ROS such as nitric oxide (NO), superoxide (O₂-), and their derivative molecules hydrogen peroxide (H₂O₂) and peroxynitrite (ONO₂-) regulate solute and water reabsorption, which is vital to maintain electrolyte homeostasis and extracellular fluid volume. This article reviews the effects of NO, O₂-, ONO₂-, and H₂O₂ on water and electrolyte reabsorption in proximal tubules, thick ascending limbs, and collecting ducts, and the effects of NO and O₂- in the macula densa on tubuloglomerular feedback.
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Affiliation(s)
- Agustin Gonzalez-Vicente
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.
- Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires C1113AAD, Argentina.
| | - Jeffrey L Garvin
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.
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7
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McDonough AA, Youn JH. Potassium Homeostasis: The Knowns, the Unknowns, and the Health Benefits. Physiology (Bethesda) 2017; 32:100-111. [PMID: 28202621 PMCID: PMC5337831 DOI: 10.1152/physiol.00022.2016] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Potassium homeostasis has a very high priority because of its importance for membrane potential. Although extracellular K+ is only 2% of total body K+, our physiology was evolutionarily tuned for a high-K+, low-Na+ diet. We review how multiple systems interface to accomplish fine K+ balance and the consequences for health and disease.
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Affiliation(s)
- Alicia A McDonough
- Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California; and
| | - Jang H Youn
- Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, California
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8
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Tamma G, Valenti G. Evaluating the Oxidative Stress in Renal Diseases: What Is the Role for S-Glutathionylation? Antioxid Redox Signal 2016; 25:147-64. [PMID: 26972776 DOI: 10.1089/ars.2016.6656] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
SIGNIFICANCE Reactive oxygen species (ROS) have long been considered as toxic derivatives of aerobic metabolism displaying a harmful effect to living cells. Deregulation of redox homeostasis and production of excessive free radicals may contribute to the pathogenesis of kidney diseases. In line, oxidative stress increases in patients with renal dysfunctions due to a general increase of ROS paralleled by impaired antioxidant ability. RECENT ADVANCES Emerging evidence revealed that physiologically, ROS can act as signaling molecules interplaying with several transduction pathways such as proliferation, differentiation, and apoptosis. ROS can exert signaling functions by modulating, at different layers, protein oxidation since proteins have "cysteine switches" that can be reversibly reduced or oxidized, supporting the dynamic signaling regulation function. In this scenario, S-glutathionylation is a posttranslational modification involved in oxidative cellular response. CRITICAL ISSUES Although it is widely accepted that renal dysfunctions are often associated with altered redox signaling, the relative role of S-glutathionylation on the pathogenesis of specific renal diseases remains unclear and needs further investigations. In this review, we discuss the impact of ROS in renal health and diseases and the role of selective S-glutathionylation proteins potentially relevant to renal physiology. FUTURE DIRECTIONS The paucity of studies linking the reversible protein glutathionylation with specific renal disorders remains unmet. The growing number of S-glutathionylated proteins indicates that this is a fascinating area of research. In this respect, further studies on the association of reversible glutathionylation with renal diseases, characterized by oxidative stress, may be useful to develop new pharmacological molecules targeting protein S-glutathionylation. Antioxid. Redox Signal. 25, 147-164.
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Affiliation(s)
- Grazia Tamma
- 1 Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari , Bari, Italy .,2 Istituto Nazionale di Biostrutture e Biosistemi (I.N.B.B.) , Rome, Italy
| | - Giovanna Valenti
- 1 Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari , Bari, Italy .,2 Istituto Nazionale di Biostrutture e Biosistemi (I.N.B.B.) , Rome, Italy .,3 Centro di Eccellenza di Genomica in campo Biomedico ed Agrario (CEGBA) , Bari, Italy
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9
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Abstract
More than two dozen types of potassium channels, with different biophysical and regulatory properties, are expressed in the kidney, influencing renal function in many important ways. Recently, a confluence of discoveries in areas from human genetics to physiology, cell biology, and biophysics has cast light on the special function of five different potassium channels in the distal nephron, encoded by the genes KCNJ1, KCNJ10, KCNJ16, KCNMA1, and KCNN3. Research aimed at understanding how these channels work in health and go awry in disease has transformed our understanding of potassium balance and provided new insights into mechanisms of renal sodium handling and the maintenance of blood pressure. This review focuses on recent advances in this rapidly evolving field.
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Affiliation(s)
- Paul A Welling
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201;
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10
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Abstract
Since the first demonstration of Nox enzyme expression in the kidney in the early 1990s and the subsequent identification of Nox4, or RENOX, a decade later, it has become apparent that the Nox family of reactive oxygen species (ROS) generating enzymes plays an integral role in the normal physiological function of the kidney. As our knowledge of Nox expression patterns and functions in various structures and specialized cell types within the kidney grows, so does the realization that Nox-derived oxidative stress contributes significantly to a wide variety of renal pathologies through their ability to modify lipids and proteins, damage DNA and activate transcriptional programmes. Diverse studies demonstrate key roles for Nox-derived ROS in kidney fibrosis, particularly in settings of chronic renal disease such as diabetic nephropathy. As the most abundant Nox family member in the kidney, much emphasis has been placed on the role of Nox4 in this setting. However, an ever growing body of work continues to uncover key roles for other Nox family members, not only in diabetic kidney disease, but in a diverse array of renal pathological conditions. The objective of the present review is to highlight the latest novel developments in renal Nox biology with an emphasis not only on diabetic nephropathy but many of the other renal disease contexts where oxidative stress is implicated.
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11
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Wang L, Zhang C, Su X, Lin DH, Wang W. Caveolin-1 Deficiency Inhibits the Basolateral K+ Channels in the Distal Convoluted Tubule and Impairs Renal K+ and Mg2+ Transport. J Am Soc Nephrol 2015; 26:2678-90. [PMID: 25848073 DOI: 10.1681/asn.2014070658] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 12/22/2014] [Indexed: 01/28/2023] Open
Abstract
Kcnj10 encodes the inwardly rectifying K(+) channel Kir4.1 in the basolateral membrane of the distal convoluted tubule (DCT) and is activated by c-Src. However, the regulation and function of this K(+) channel are incompletely characterized. Here, patch-clamp experiments in Kcnj10-transfected HEK293 cells demonstrated that c-Src-induced stimulation of Kcnj10 requires coexpression of caveolin-1 (cav-1), and immunostaining showed expression of cav-1 in the basolateral membrane of parvalbumin-positive DCT. Patch-clamp experiments detected a 40-pS inwardly rectifying K(+) channel, a heterotetramer of Kir4.1/Kir5.1, in the basolateral membrane of the early DCT (DCT1) in both wild-type (WT) and cav-1-knockout (KO) mice. However, the activity of this basolateral 40-pS K(+) channel was lower in KO mice than in WT mice. Moreover, the K(+) reversal potential (an indication of membrane potential) was less negative in the DCT1 of KO mice than in the DCT1 of WT mice. Western blot analysis demonstrated that cav-1 deficiency decreased the expression of the Na(+)/Cl(-) cotransporter and Ste20-proline-alanine-rich kinase (SPAK) but increased the expression of epithelial Na(+) channel-α. Furthermore, the urinary excretion of Mg(2+) and K(+) was significantly higher in KO mice than in WT mice, and KO mice developed hypomagnesemia, hypocalcemia, and hypokalemia. We conclude that disruption of cav-1 decreases basolateral K(+) channel activity and depolarizes the cell membrane potential in the DCT1 at least in part by suppressing the stimulatory effect of c-Src on Kcnj10. Furthermore, the decrease in Kcnj10 and Na(+)/Cl(-) cotransporter expression induced by cav-1 deficiency may underlie the compromised renal transport of Mg(2+), Ca(2+), and K(+).
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Affiliation(s)
- Lijun Wang
- Department of Physiology, Harbin Medical University, Harbin, China; Department of Pharmacology, New York Medical College, Valhalla, New York; and
| | - Chengbiao Zhang
- Department of Pharmacology, New York Medical College, Valhalla, New York; and Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical College, Xuzhou, China
| | - Xiaotong Su
- Department of Pharmacology, New York Medical College, Valhalla, New York; and
| | - Dao-Hong Lin
- Department of Pharmacology, New York Medical College, Valhalla, New York; and
| | - Wenhui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York; and
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12
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Wang WH, Zhang C, Lin DH, Wang L, Graves JP, Zeldin DC, Capdevila JH. Cyp2c44 epoxygenase in the collecting duct is essential for the high K+ intake-induced antihypertensive effect. Am J Physiol Renal Physiol 2014; 307:F453-60. [PMID: 24966089 DOI: 10.1152/ajprenal.00123.2014] [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] [Indexed: 02/04/2023] Open
Abstract
Cytochrome P-450, family 2, subfamily c, polypeptide 44 (Cyp2c44) epoxygenase metabolizes arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs) in kidney and vascular tissues. In the present study, we used real-time quantitative PCR techniques to examine the effect of high salt or high K(+) (HK) intake on the expression of Cyp2c44, a major Cyp2c epoxygenase in the mouse kidney. We detected Cyp2c44 in the proximal convoluted tubule, thick ascending limb, distal convoluted tubule (DCT)/connecting tubule (CNT), and collecting duct (CD). A high-salt diet increased the expression of Cyp2c44 in the thick ascending limb and DCT/CNT but not in the proximal convoluted tubule and CD. In contrast, an increase in dietary K(+) intake augmented Cyp2c44 expression only in the DCT/CNT and CD. Neither high salt nor HK intake had a significant effect on the blood pressure (BP) of wild-type mice. However, HK but not high salt intake increased BP in CD-specific, Cyp2c44 conditional knockout (KO) mice. Amiloride, an epithelial Na(+) channel (ENaC) inhibitor, normalized the BP of KO mice fed HK diets, suggesting that lack of Cyp2c44 in the CD enhances ENaC activity and increases Na(+) absorption in KO mice fed HK diets. This notion was supported by metabolic cage experiments demonstrating that renal Na(+) excretion was compromised in KO mice fed HK diets. Also, patch-clamp experiments demonstrated that 11,12-EET, a major Cyp2c44 product, but not AA inhibited ENaC activity in the cortical CD of KO mice. We conclude that Cyp2c44 in the CD is required for preventing the excessive Na(+) absorption induced by HK intake by inhibition of ENaC and facilitating renal Na(+) excretion.
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Affiliation(s)
- Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York;
| | - Chengbiao Zhang
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Dao-Hong Lin
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Lijun Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Joan P Graves
- Division of Intramural Research, National Institute of Environmental Health Science, Research Triangle Park, North Carolina; and
| | - Darryl C Zeldin
- Division of Intramural Research, National Institute of Environmental Health Science, Research Triangle Park, North Carolina; and
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Abstract
Extracellular K(+) homeostasis has been explained by feedback mechanisms in which changes in extracellular K(+) concentration drive renal K(+) excretion directly or indirectly via stimulating aldosterone secretion. However, this cannot explain meal-induced kaliuresis, which often occurs without increases in plasma K(+) or aldosterone concentrations. Recent studies have produced evidence supporting a feedforward control in which gut sensing of dietary K(+) increases renal K(+) excretion (and extrarenal K(+) uptake) independent of plasma K(+) concentrations, namely, a gut factor. This review focuses on these new findings and discusses the role of gut factor in acute and chronic regulation of extracellular K(+) as well as in the beneficial effects of high K(+) intake on the cardiovascular system.
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Affiliation(s)
- Jang H Youn
- Department of Physiology and Biophysics, University of Southern California Keck School of Medicine, Los Angeles, CA 90089-9142, USA.
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14
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Féraille E, Dizin E, Roth I, Derouette JP, Szanto I, Martin PY, de Seigneux S, Hasler U. NADPH oxidase 4 deficiency reduces aquaporin-2 mRNA expression in cultured renal collecting duct principal cells via increased PDE3 and PDE4 activity. PLoS One 2014; 9:e87239. [PMID: 24466344 PMCID: PMC3900718 DOI: 10.1371/journal.pone.0087239] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 12/19/2013] [Indexed: 11/24/2022] Open
Abstract
The final control of renal water reabsorption occurs in the collecting duct (CD) and relies on regulated expression of aquaporin-2 (AQP2) in principal CD cells. AQP2 transcription is primarily induced by type 2 vasopressin receptor (V2R)-cAMP-protein kinase A (PKA) signaling but also by other factors, including TonEBP and NF-κB. NAPDH oxidase 4 (NOX4) represents a major source of reactive oxygen species (ROS) in the kidney. Because NOX-derived ROS may alter PKA, TonEBP and NF-κB activity, we examined the effects of NOX4 depletion on AQP2 expression. Depleted NOX4 expression by siRNA (siNOX4) in mpkCCDcl4 cells attenuated increased AQP2 mRNA expression by arginine vasopressin (AVP) but not by hypertonicity, which induces both TonEBP and NF-κB activity. AVP-induced AQP2 expression was similarly decreased by the flavoprotein inhibitor diphenyleneiodonium. siNOX4 altered neither TonEBP nor NF-κB activity but attenuated AVP-inducible cellular cAMP concentration, PKA activity and CREB phosphorylation as well as AQP2 mRNA expression induced by forskolin, a potent activator of adenylate cyclase. The repressive effect of siNOX4 on AVP-induced AQP2 mRNA expression was abolished by the non-selective phosphodiesterase (PDE) inhibitor 3-isobutyl-1-methylxanthine (IBMX) and was significantly decreased by selective PDE antagonists cilostamide and rolipram, but not vinpocetine, which respectively target PDE3, PDE4 and PDE1. Thus, by inhibiting PDE3 and PDE4 activity NOX4-derived ROS may contribute to V2R-cAMP-PKA signaling and enhance AQP2 transcription.
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Affiliation(s)
- Eric Féraille
- Departments of Cellular Physiology and Metabolism, University Medical Center, Geneva, Switzerland
| | - Eva Dizin
- Departments of Cellular Physiology and Metabolism, University Medical Center, Geneva, Switzerland
| | - Isabelle Roth
- Departments of Cellular Physiology and Metabolism, University Medical Center, Geneva, Switzerland
| | - Jean-Paul Derouette
- Departments of Cellular Physiology and Metabolism, University Medical Center, Geneva, Switzerland
| | - Ildiko Szanto
- Departments of Cellular Physiology and Metabolism, University Medical Center, Geneva, Switzerland
- Service of Endocrinology, Diabetology, Hypertension and Nutrition, Department of Medical Specialties, University of Geneva, Geneva, Switzerland
| | - Pierre-Yves Martin
- Service of Nephrology, Department of Medical Specialties, University of Geneva, Geneva, Switzerland
| | - Sophie de Seigneux
- Service of Nephrology, Department of Medical Specialties, University of Geneva, Geneva, Switzerland
| | - Udo Hasler
- Departments of Cellular Physiology and Metabolism, University Medical Center, Geneva, Switzerland
- * E-mail:
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15
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Sedeek M, Nasrallah R, Touyz RM, Hébert RL. NADPH oxidases, reactive oxygen species, and the kidney: friend and foe. J Am Soc Nephrol 2013; 24:1512-8. [PMID: 23970124 DOI: 10.1681/asn.2012111112] [Citation(s) in RCA: 335] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Reactive oxygen species (ROS) play an important role in normal cellular physiology. They regulate different biologic processes such as cell defense, hormone synthesis and signaling, activation of G protein-coupled receptors, and ion channels and kinases/phosphatases. ROS are also important regulators of transcription factors and gene expression. On the other hand, in pathologic conditions, a surplus of ROS in tissue results in oxidative stress with various injurious consequences such as inflammation and fibrosis. NADPH oxidases are one of the many sources of ROS in biologic systems, and there are seven isoforms (Nox1-5, Duox1, Duox2). Nox4 is the predominant form in the kidney, although Nox2 is also expressed. Nox4 has been implicated in the basal production of ROS in the kidney and in pathologic conditions such as diabetic nephropathy and CKD; upregulation of Nox4 may be important in renal oxidative stress and kidney injury. Although there is growing evidence indicating the involvement of NADPH oxidase in renal pathology, there is a paucity of information on the role of NADPH oxidase in the regulation of normal renal function. Here we provide an update on the role of NADPH oxidases and ROS in renal physiology and pathology.
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Affiliation(s)
- Mona Sedeek
- Kidney Research Centre, Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Ontario, Canada
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16
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Abstract
Angiotensin II (Ang II) is the principal effector of the renin-angiotensin-aldosterone system (RAAS). It initiates myriad processes in multiple organs integrated to increase circulating volume and elevate systemic blood pressure. In the kidney, Ang II stimulates renal tubular water and salt reabsorption causing antinatriuresis and antidiuresis. Activation of the RAAS is known to enhance activity of the epithelial Na(+) channel (ENaC) in the aldosterone-sensitive distal nephron. In addition to its well described stimulatory actions on aldosterone secretion, Ang II is also capable of directly increasing ENaC activity. In this brief review, we discuss recent findings about non-classical Ang II actions on ENaC and speculate about its relevance for renal sodium handling.
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17
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Wu P, Wang M, Luan H, Li L, Wang L, Wang W, Gu R. Angiotensin II stimulates basolateral 10-pS Cl channels in the thick ascending limb. Hypertension 2013; 61:1211-7. [PMID: 23569086 PMCID: PMC3686115 DOI: 10.1161/hypertensionaha.111.01069] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 03/09/2013] [Indexed: 02/07/2023]
Abstract
Chloride channels in the basolateral membrane play a key role in Cl absorption in the thick ascending limb (TAL). The patch-clamp experiments were performed to test whether angiotensin II (AngII) increases Cl absorption in the TAL by stimulating the basolateral 10-pS Cl channels. AngII (1-100 nmol/L) stimulated the 10-pS Cl channel in the TAL, an effect that was blocked by losartan (angiotension AT1 receptor [AT1R] antagonist) but not by PD123319 (angiotension AT2 receptor [AT2R] antagonist). Inhibition of phospholipase C or protein kinase C also abolished the stimulatory effect of AngII on Cl channels. Moreover, stimulation of protein kinase C with phorbol-12-myristate-13-acetate mimicked the effect of AngII and increased Cl channel activity. However, the stimulatory effect of AngII on Cl channels was absent in the TAL pretreated with diphenyleneiodonium sulfate, an inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Moreover, treatment of the TAL with diphenyleneiodonium sulfate also blocked the effect of phorbol-12-myristate-13-acetate on the 10-pS Cl channel. Western blotting demonstrated that incubation of isolated TAL with AngII increased phosphorylation of p47(phox) at Ser(304), suggesting that AngII stimulates the basolateral Cl channels by increasing NADPH oxidase-dependent superoxide generation. This notion was also supported by the observation that H2O2 significantly increased 10-pS Cl channel activity in the TAL. We conclude that stimulation of AT1R increased the basolateral Cl channels by activating the protein kinase C-dependent NADPH oxidase pathway. The stimulatory effect of AngII on the basolateral Cl channel may contribute to AngII-induced increases in NaCl reabsorption in the TAL and AngII-infuse-induced hypertension.
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Affiliation(s)
- Peng Wu
- Department of Pharmacology, Harbin Medical University, Harbin, China
| | - Mingxiao Wang
- Department of Pharmacology, Harbin Medical University, Harbin, China
| | - Haiyan Luan
- Department of Pharmacology, Harbin Medical University, Harbin, China
| | - Lili Li
- Department of Pharmacology, Harbin Medical University, Harbin, China
| | - Lijun Wang
- Department of Physiology, Harbin Medical University, Harbin, China
- Department of Pharmacology, New York Medical College, Valhalla, NY
| | - Wenhui Wang
- Department of Pharmacology, New York Medical College, Valhalla, NY
| | - Ruimin Gu
- Department of Pharmacology, Harbin Medical University, Harbin, China
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18
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Sun P, Yue P, Wang WH. Angiotensin II stimulates epithelial sodium channels in the cortical collecting duct of the rat kidney. Am J Physiol Renal Physiol 2012; 302:F679-87. [PMID: 22169010 PMCID: PMC3311319 DOI: 10.1152/ajprenal.00368.2011] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Accepted: 12/06/2011] [Indexed: 02/07/2023] Open
Abstract
We examined the effect of angiotensin II (ANG II) on epithelial Na(+) channel (ENaC) in the rat cortical collecting duct (CCD) with single-channel and the perforated whole cell patch-clamp recording. Application of 50 nM ANG II increased ENaC activity, defined by NP(o) (a product of channel numbers and open probability), and the amiloride-sensitive whole cell Na currents by twofold. The stimulatory effect of ANG II on ENaC was absent in the presence of losartan, suggesting that the effect of ANG II on ENaC was mediated by ANG II type 1 receptor. Moreover, depletion of intracellular Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA)-AM failed to abolish the stimulatory effect of ANG II on ENaC but inhibiting protein kinase C (PKC) abolished the effect of ANG II, suggesting that the effect of ANG II was the result of stimulating Ca(2+)-independent PKC. This notion was also suggested by the experiments in which stimulation of PKC with phorbol ester derivative mimicked the effect of ANG II and increased amiloride-sensitive Na currents in the principal cell, an effect that was not abolished by treatment of the CCD with BAPTA-AM. Also, inhibition of NADPH oxidase (NOX) with diphenyleneiodonium chloride abolished the stimulatory effect of ANG II on ENaC and application of superoxide donors, pyrogallol or xanthine and xanthine oxidase, significantly increased ENaC activity. Moreover, addition of ANG II or H(2)O(2) diminished the arachidonic acid (AA)-induced inhibition of ENaC in the CCD. We conclude that ANG II stimulates ENaC in the CCD through a Ca(2+)-independent PKC pathway that activates NOX thereby increasing superoxide generation. The stimulatory effect of ANG II on ENaC may be partially the result of blocking AA-induced inhibition of ENaC.
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Affiliation(s)
- Peng Sun
- Dept. of Pharmacology, New York Medical College, 15 Dana Rd., Valhalla, NY 10595, USA
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19
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Sun P, Antoun J, Lin DH, Yue P, Gotlinger KH, Capdevila J, Wang WH. Cyp2c44 epoxygenase is essential for preventing the renal sodium absorption during increasing dietary potassium intake. Hypertension 2011; 59:339-47. [PMID: 22184322 DOI: 10.1161/hypertensionaha.111.178475] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The aim of this study is to test whether the Cyp2c44 epoxygenase-dependent metabolism of arachidonic acid prevents the hypertensive effect of a high K (HK) intake by inhibiting the epithelial sodium channel (ENaC) activity. A HK intake elevated Cyp2c44 mRNA expression and 11,12-epoxyeicosatrienoic acid levels in the cortical collecting duct in Cyp2c44(+/+) mice (wild-type [wt]). However, an HK intake failed to increase 11,12-epoxyeicosatrienoic acid formation in the cortical collecting ducts of Cyp2c44(-/-) mice. Moreover, increasing K intake enhanced arachidonic acid-induced inhibition of ENaC in the wt but not in Cyp2c44(-/-) mice. In contrast, 11,12-epoxyeicosatrienoic acid, a Cyp2c44 metabolite, inhibited ENaC in the wt and Cyp2c44(-/-) mice. The notion that Cyp2c44 is the epoxygenase responsible for mediating the inhibitory effects of arachidonic acid on ENaC is further suggested by the observation that inhibiting Cyp-epoxygenase increased the whole-cell Na currents in principal cells of wt but not in Cyp2c44(-/-) mice. Feeding mice with an HK diet raised the systemic blood pressures of Cyp2c44(-/-) mice but was without an effect on wt mice. Moreover, application of amiloride abolished the HK-induced hypertension in Cyp2c44(-/-) mice. The HK-induced hypertension of Cyp2c44(-/-) mice was accompanied by decreasing 24-hour urinary Na excretion and increasing the plasma Na concentration, and the effects were absent in wt mice. In contrast, disruption of the Cyp2c44 gene did not alter K excretion. We conclude that Cyp2c44 epoxygenase mediates the inhibitory effect of arachidonic acid on ENaC and that Cyp2c44 functions as an HK-inducible antihypertensive enzyme responsible for inhibiting ENaC activity and Na absorption in the aldosterone-sensitive distal nephron.
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Affiliation(s)
- Peng Sun
- Department of Pharmacology, New York Medical College, 15 Dana Rd, Valhalla, NY 10595, USA
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20
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Schreck C, O'Connor PM. NAD(P)H oxidase and renal epithelial ion transport. Am J Physiol Regul Integr Comp Physiol 2011; 300:R1023-9. [PMID: 21270341 DOI: 10.1152/ajpregu.00618.2010] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
A fundamental requirement for cellular vitality is the maintenance of plasma ion concentration within strict ranges. It is the function of the kidney to match urinary excretion of ions with daily ion intake and nonrenal losses to maintain a stable ionic milieu. NADPH oxidase is a source of reactive oxygen species (ROS) within many cell types, including the transporting renal epithelia. The focus of this review is to describe the role of NADPH oxidase-derived ROS toward local renal tubular ion transport in each nephron segment and to discuss how NADPH oxidase-derived ROS signaling within the nephron may mediate ion homeostasis. In each case, we will attempt to identify the various subunits of NADPH oxidase and reactive oxygen species involved and the ion transporters, which these affect. We will first review the role of NADPH oxidase on renal Na(+) and K(+) transport. Finally, we will review the relationship between tubular H(+) efflux and NADPH oxidase activity.
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21
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Wang ZJ, Sun P, Xing W, Pan C, Lin DH, Wang WH. Decrease in dietary K intake stimulates the generation of superoxide anions in the kidney and inhibits K secretory channels in the CCD. Am J Physiol Renal Physiol 2010; 298:F1515-22. [PMID: 20357031 DOI: 10.1152/ajprenal.00502.2009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We previously demonstrated that K depletion inhibited ROMK-like small-conductance K channels (SK) in the cortical collecting duct (CCD) and that the effect was mediated by superoxide anions that stimulated Src family protein tyrosine kinase (PTK) and mitogen-activated protein kinase (MAPK) (51). However, because animals on a K-deficient diet had a severe hypokalemia, superoxide-dependent signaling may not regulate ROMK channels under physiological conditions with a normal plasma K concentration. In the present study, we used the patch-clamp technique and Western blot to examine the effect of a moderate K restriction on ROMK-like SK channels and the role of PTK and MAPK in regulating apical K channels in the CCD of animals on a low-K diet (LK; 0.1% K). Rats and mice fed a LK diet for 7 days had a normal plasma K concentration. However, a LK intake increased the expression of angiotensin II type 1 receptor in the kidney. Moreover, patch-clamp experiments demonstrated that LK intake decreased the probability finding SK channels and channel activity defined by NP(o) (a product of channel number and open probability) in the CCD of both rat and mouse kidneys. Also, LK intake significantly stimulated the production of superoxide anions in the renal cortex and outer medulla in both rats and mice and increased superoxide level in the rat CCD. Moreover, LK intake augments the phosphorylation of p38 and ERK MAPK, the expression of c-Src and tyrosine phosphorylation of ROMK channels. However, treatment of animals with tempol abolished the effect of LK intake on MAPK and c-Src and increased ROMK channel activity in comparing with those of nontreated rats on a LK diet. Inhibiting p38 and ERK with SB202190 and PD98059 significantly stimulated SK in the CCD in rats on a LK diet. In addition, inhibition of PTK with herbimycin A activated SK channels in the CCD from rats on a LK diet. We conclude that LK intake stimulates the generation of superoxide anion and related products and that MAPK and Src family PTK play a physiological role in inhibiting apical K channels in the principal cells in response to LK intake.
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Affiliation(s)
- Zhi-Jian Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York 10595, USA
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22
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Youn JH, McDonough AA. Recent advances in understanding integrative control of potassium homeostasis. Annu Rev Physiol 2009; 71:381-401. [PMID: 18759636 DOI: 10.1146/annurev.physiol.010908.163241] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The potassium homeostatic system is very tightly regulated. Recent studies have shed light on the sensing and molecular mechanisms responsible for this tight control. In addition to classic feedback regulation mediated by a rise in extracellular fluid (ECF) [K(+)], there is evidence for a feedforward mechanism: Dietary K(+) intake is sensed in the gut, and an unidentified gut factor is activated to stimulate renal K(+) excretion. This pathway may explain renal and extrarenal responses to altered K(+) intake that occur independently of changes in ECF [K(+)]. Mechanisms for conserving ECF K(+) during fasting or K(+) deprivation have been described: Kidney NADPH oxidase activation initiates a cascade that provokes the retraction of K(+) channels from the cell membrane, and muscle becomes resistant to insulin stimulation of cellular K(+) uptake. How these mechanisms are triggered by K(+) deprivation remains unclear. Cellular AMP kinase-dependent protein kinase activity provokes the acute transfer of K(+) from the ECF to the ICF, which may be important in exercise or ischemia. These recent advances may shed light on the beneficial effects of a high-K(+) diet for the cardiovascular system.
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Affiliation(s)
- Jang H Youn
- Department of Physiology and Biophysics, University of Southern California Keck School of Medicine, Los Angeles, California 90089-9142, USA.
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23
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Greenlee M, Wingo CS, McDonough AA, Youn JH, Kone BC. Narrative review: evolving concepts in potassium homeostasis and hypokalemia. Ann Intern Med 2009; 150:619-25. [PMID: 19414841 PMCID: PMC4944758 DOI: 10.7326/0003-4819-150-9-200905050-00008] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Humans are intermittently exposed to large variations in potassium intake, which range from periods of fasting to ingestion of potassium-rich meals. These fluctuations would abruptly alter plasma potassium concentration if not for rapid mechanisms, primarily in skeletal muscle and the liver, that buffer the changes in plasma potassium concentration by means of transcellular potassium redistribution and feedback control of renal potassium excretion. However, buffers have capacity limits, and even robust feedback control mechanisms require that the perturbation occur before feedback can initiate corrective action. In contrast, feedforward control mechanisms sense the effect of disturbances on the system's homeostasis. This review highlights recent experimental insights into the participation of feedback and feedforward control mechanisms in potassium homeostasis. New data make clear that feedforward homeostatic responses activate when decreased potassium intake is sensed, even when plasma potassium concentration is still within the normal range and before frank hypokalemia ensues, in addition to the classic feedback activation of renal potassium conservation when plasma potassium concentration decreases. Given the clinical importance of dyskalemias in patients, these novel experimental paradigms invite renewed clinical inquiry into this important area.
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Affiliation(s)
- Megan Greenlee
- University of Florida College of Medicine and Department of Veterans Affairs Medical Center, Gainesville, Florida 32610, USA
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24
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Wang WH, Giebisch G. Regulation of potassium (K) handling in the renal collecting duct. Pflugers Arch 2009; 458:157-68. [PMID: 18839206 PMCID: PMC2730119 DOI: 10.1007/s00424-008-0593-3] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Accepted: 09/20/2008] [Indexed: 12/13/2022]
Abstract
This review provides an overview of the molecular mechanisms of K transport in the mammalian connecting tubule (CNT) and cortical collecting duct (CCD), both nephron segments responsible for the regulation of renal K secretion. Aldosterone and dietary K intake are two of the most important factors regulating K secretion in the CNT and CCD. Recently, angiotensin II (AngII) has also been shown to play a role in the regulation of K secretion. In addition, genetic and molecular biological approaches have further identified new mechanisms by which aldosterone and dietary K intake regulate K transport. Thus, the interaction between serum-glucocorticoid-induced kinase 1 (SGK1) and with-no-lysine kinase 4 (WNK4) plays a significant role in mediating the effect of aldosterone on ROMK (Kir1.1), an important apical K channel modulating K secretion. Recent evidence suggests that WNK1, mitogen-activated protein kinases such as P38, ERK, and Src family protein tyrosine kinase are involved in mediating the effect of low K intake on apical K secretory channels.
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Affiliation(s)
- Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, 10595, USA.
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25
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Jin Y, Wang Y, Wang ZJ, Lin DH, Wang WH. Inhibition of angiotensin type 1 receptor impairs renal ability of K conservation in response to K restriction. Am J Physiol Renal Physiol 2009; 296:F1179-84. [PMID: 19211683 DOI: 10.1152/ajprenal.90725.2008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We have previously demonstrated that ANG II inhibits ROMK-like small-conductance K channels (SK) in the cortical collecting duct from rats on a K-deficient diet (KD) (35). In the present study, we examined the role of angiotensin type 1 receptor (AT(1)R) in mediating the effect of K restriction on K secretion. We confirmed the previous finding that K restriction increased the superoxide anion level, c-Src expression, and the phosphorylation of both p38 and extracellular signal-regulated kinase mitogen-activated protein kinase (MAPK) in renal cortex and outer medulla. However, the effect of K restriction on superoxide anion generation, c-Src expression, and MAPK phosphorylation was significantly attenuated in rats receiving losartan, an inhibitor of AT(1)R. In contrast, losartan treatment had no effect on superoxide anion level, c-Src expression, and MAPK phosphorylation in animals on a normal K diet (NK). K restriction decreased SK channel activity and increased the tyrosine phosphorylation of ROMK. However, inhibiting AT(1)R abolished the effect of K restriction on SK channels and tyrosine phosphorylation of ROMK channels. The notion that AT(1)R is involved in regulating renal K excretion was also supported by the experiments with metabolic cages showing that losartan treatment significantly enhanced urinary K loss in rats on a KD diet while it had no effect in animals on a NK diet. Consequently, losartan-treated animals had severe hypokalemia in response to K restriction compared with rats without losartan intake. We conclude that AT(1)R is involved in mediating the effect of K restriction on superoxide generation, c-Src, and MAPK and that inhibiting AT(1)R impairs renal ability of K conservation in response to K depletion.
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Affiliation(s)
- Yan Jin
- Department of Medical Genetics, Harbin Medical University, Harbin, China
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26
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PGE2 inhibits basolateral 50 pS potassium channels in the thick ascending limb of the rat kidney. Kidney Int 2008; 74:478-85. [PMID: 18496512 DOI: 10.1038/ki.2008.198] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
To study the inhibition of the inwardly rectifying basolateral 50 pS potassium channels by PGE(2) we performed patch-clamp studies on the basolateral membrane of the rat kidney thick ascending limb. PGE(2)'s effect was mimicked by the selective EP1- and EP3-receptor agonist, sulprostone, but was prevented by inhibiting protein kinase-C with calphostin-C. The mitogen-activated protein kinase inhibitor PD98059 (ERK) or SB203580 (p38) increased basal channel activity; however, while neither alone prevented the inhibitory effect of PGE(2), but using both of them together completely abolished PGE(2)'s effect on channel activity. Treatment with PGE(2) stimulated phosphorylation of both p38 and ERK in primary cultures of medullary thick ascending limb cells. The PGE(2)-mediated mitogen-activated protein kinase activation was not affected by indomethacin, but was completely blocked by calphostin-C. These studies show that inhibition of basolateral 50 pS potassium channels by PGE(2) is mediated by protein kinase-C, which in turn stimulates mitogen-activated protein kinases in the thick ascending limb of the rat kidney.
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27
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Zhang Y, Lin DH, Wang ZJ, Jin Y, Yang B, Wang WH. K restriction inhibits protein phosphatase 2B (PP2B) and suppression of PP2B decreases ROMK channel activity in the CCD. Am J Physiol Cell Physiol 2008; 294:C765-73. [PMID: 18184875 DOI: 10.1152/ajpcell.00528.2007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We used Western blot analysis to examine the effect of dietary K intake on the expression of serine/threonine protein phosphatase in the kidney. K restriction significantly decreased the expression of catalytic subunit of protein phosphatase (PP)2B but increased the expression of PP2B regulatory subunit in both rat and mouse kidney. However, K depletion did not affect the expression of PP1 and PP2A. Treatment of M-1 cells, mouse cortical collecting duct (CCD) cells, or 293T cells with glucose oxidase (GO), which generates superoxide anions through glucose metabolism, mimicked the effect of K restriction on PP2B expression and significantly decreased expression of PP2B catalytic subunits. However, GO treatment increased expression of regulatory subunit of PP2B and had no effect on expression of PP1, PP2A, and protein tyrosine phosphatase 1D. Moreover, deletion of gp91-containing NADPH oxidase abolished the effect of K depletion on PP2B. Thus superoxide anions or related products may mediate the inhibitory effect of K restriction on the expression of PP2B catalytic subunit. We also used patch-clamp technique to study the effect of inhibiting PP2B on renal outer medullary K (ROMK) channels in the CCD. Application of cyclosporin A or FK506, inhibitors of PP2B, significantly decreased ROMK channels, and the effect of PP2B inhibitors was abolished by blocking p38 mitogen-activated protein kinase (MAPK) and ERK. Furthermore, Western blot demonstrated that inhibition of PP2B with cyclosporin A or small interfering RNA increased the phosphorylation of ERK and p38 MAPK. We conclude that K restriction suppresses the expression of PP2B catalytic subunits and that inhibition of PP2B decreases ROMK channel activity through stimulation of MAPK in the CCD.
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Affiliation(s)
- Yan Zhang
- Department of Pharmacology, Harbin Medical University, Harbin, China
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