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Lombari P, Mallardo M, Petrazzuolo O, Amruthraj Nagoth J, Fiume G, Scanni R, Iervolino A, Damiano S, Coppola A, Borriello M, Ingrosso D, Perna AF, Zacchia M, Trepiccione F, Capasso G. miRNA-23a modulates sodium-hydrogen exchanger 1 expression: studies in medullary thick ascending limb of salt-induced hypertensive rats. Nephrol Dial Transplant 2023; 38:586-598. [PMID: 35921220 DOI: 10.1093/ndt/gfac232] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The kidney is the main organ in the pathophysiology of essential hypertension. Although most bicarbonate reabsorption occurs in the proximal tubule, the medullary thick ascending limb (mTAL) of the nephron also maintains acid-base balance by contributing to 25% of bicarbonate reabsorption. A crucial element in this regulation is the sodium-hydrogen exchanger 1 (NHE1), a ubiquitous membrane protein controlling intracellular pH, where proton extrusion is driven by the inward sodium flux. MicroRNA (miRNA) expression of hypertensive patients significantly differs from that of normotensive subjects. The aim of this study was to determine the functional role of miRNA alterations at the mTAL level. METHODS By miRNA microarray analysis, we identified miRNA expression profiles in isolated mTALs from high sodium intake-induced hypertensive rats (HSD) versus their normotensive counterparts (NSD). In vitro validation was carried out in rat mTAL cells. RESULTS Five miRNAs involved in the onset of salt-sensitive hypertension were identified, including miR-23a, which was bioinformatically predicted to target NHE1 mRNA. Data demonstrated that miRNA-23a is downregulated in the mTAL of HSD rats while NHE1 is upregulated. Consistently, transfection of an miRNA-23a mimic in an mTAL cell line, using a viral vector, resulted in NHE1 downregulation. CONCLUSION NHE1, a protein involved in sodium reabsorption at the mTAL level and blood pressure regulation, is upregulated in our model. This was due to a downregulation of miRNA-23a. Expression levels of this miRNA are influenced by high sodium intake in the mTALs of rats. The downregulation of miRNA-23a in humans affected by essential hypertension corroborate our data and point to the potential role of miRNA-23a in the regulation of mTAL function following high salt intake.
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Affiliation(s)
- Patrizia Lombari
- Department of Precision Medicine, University of Campania "L. Vanvitelli", Naples, Italy.,Division of Nephrology, Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Massimo Mallardo
- Department of Molecular Medicine and Medical Biotechnology, University of Naples "Federico II", Naples, Italy
| | - Oriana Petrazzuolo
- Division of Nephrology, Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Joseph Amruthraj Nagoth
- Division of Nephrology, Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Giuseppe Fiume
- Departments of Experimental and Clinical Medicine, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Roberto Scanni
- Division of Nephrology, Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Anna Iervolino
- Biogem, Institute of Molecular Biology and Genetics, Ariano Irpino, Italy
| | - Sara Damiano
- Department of Veterinary Medicine and Animal Production, University of Naples "Federico II", Naples, Italy
| | - Annapaola Coppola
- Department of Precision Medicine, University of Campania "L. Vanvitelli", Naples, Italy
| | - Margherita Borriello
- Department of Precision Medicine, University of Campania "L. Vanvitelli", Naples, Italy
| | - Diego Ingrosso
- Department of Precision Medicine, University of Campania "L. Vanvitelli", Naples, Italy
| | - Alessandra F Perna
- Division of Nephrology, Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Miriam Zacchia
- Division of Nephrology, Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy
| | - Francesco Trepiccione
- Division of Nephrology, Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy.,Biogem, Institute of Molecular Biology and Genetics, Ariano Irpino, Italy
| | - Giovambattista Capasso
- Division of Nephrology, Department of Translational Medical Sciences, University of Campania "L. Vanvitelli", Naples, Italy.,Biogem, Institute of Molecular Biology and Genetics, Ariano Irpino, Italy
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Olsen JSM, Svendsen S, Berg P, Dam VS, Sorensen MV, Matchkov VV, Leipziger J, Boedtkjer E. NBCn1 Increases NH 4 + Reabsorption Across Thick Ascending Limbs, the Capacity for Urinary NH 4 + Excretion, and Early Recovery from Metabolic Acidosis. J Am Soc Nephrol 2021; 32:852-865. [PMID: 33414245 PMCID: PMC8017549 DOI: 10.1681/asn.2019060613] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2020] [Accepted: 11/23/2020] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND The electroneutral Na+/HCO3 - cotransporter NBCn1 (Slc4a7) is expressed in basolateral membranes of renal medullary thick ascending limbs (mTALs). However, direct evidence that NBCn1 contributes to acid-base handling in mTALs, urinary net acid excretion, and systemic acid-base homeostasis has been lacking. METHODS Metabolic acidosis was induced in wild-type and NBCn1 knockout mice. Fluorescence-based intracellular pH recordings were performed and NH4 + transport measured in isolated perfused mTALs. Quantitative RT-PCR and immunoblotting were used to evaluate NBCn1 expression. Tissue [NH4 +] was measured in renal biopsies, NH4 + excretion and titratable acid quantified in spot urine, and arterial blood gasses evaluated in normoventilated mice. RESULTS Basolateral Na+/HCO3 - cotransport activity was similar in isolated perfused mTALs from wild-type and NBCn1 knockout mice under control conditions. During metabolic acidosis, basolateral Na+/HCO3 - cotransport activity increased four-fold in mTALs from wild-type mice, but remained unchanged in mTALs from NBCn1 knockout mice. Correspondingly, NBCn1 protein expression in wild-type mice increased ten-fold in the inner stripe of renal outer medulla during metabolic acidosis. During systemic acid loading, knockout of NBCn1 inhibited the net NH4 + reabsorption across mTALs by approximately 60%, abolished the renal corticomedullary NH4 + gradient, reduced the capacity for urinary NH4 + excretion by approximately 50%, and delayed recovery of arterial blood pH and standard [HCO3 -] from their initial decline. CONCLUSIONS During metabolic acidosis, NBCn1 is required for the upregulated basolateral HCO3 - uptake and transepithelial NH4 + reabsorption in mTALs, renal medullary NH4 + accumulation, urinary NH4 + excretion, and early recovery of arterial blood pH and standard [HCO3 -]. These findings support that NBCn1 facilitates urinary net acid excretion by neutralizing intracellular H+ released during NH4 + reabsorption across mTALs.
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Affiliation(s)
| | - Samuel Svendsen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Peder Berg
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Vibeke S. Dam
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | | | | | - Jens Leipziger
- Department of Biomedicine, Aarhus University, Aarhus, Denmark,Aarhus Institute of Advanced Studies, Aarhus University, Aarhus, Denmark
| | - Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
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3
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Pedersen SF, Counillon L. The SLC9A-C Mammalian Na +/H + Exchanger Family: Molecules, Mechanisms, and Physiology. Physiol Rev 2019; 99:2015-2113. [PMID: 31507243 DOI: 10.1152/physrev.00028.2018] [Citation(s) in RCA: 103] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Na+/H+ exchangers play pivotal roles in the control of cell and tissue pH by mediating the electroneutral exchange of Na+ and H+ across cellular membranes. They belong to an ancient family of highly evolutionarily conserved proteins, and they play essential physiological roles in all phyla. In this review, we focus on the mammalian Na+/H+ exchangers (NHEs), the solute carrier (SLC) 9 family. This family of electroneutral transporters constitutes three branches: SLC9A, -B, and -C. Within these, each isoform exhibits distinct tissue expression profiles, regulation, and physiological roles. Some of these transporters are highly studied, with hundreds of original articles, and some are still only rudimentarily understood. In this review, we present and discuss the pioneering original work as well as the current state-of-the-art research on mammalian NHEs. We aim to provide the reader with a comprehensive view of core knowledge and recent insights into each family member, from gene organization over protein structure and regulation to physiological and pathophysiological roles. Particular attention is given to the integrated physiology of NHEs in the main organ systems. We provide several novel analyses and useful overviews, and we pinpoint main remaining enigmas, which we hope will inspire novel research on these highly versatile proteins.
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Affiliation(s)
- S F Pedersen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - L Counillon
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
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4
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Natochin YV, Golosova DV. Vasopressin receptor subtypes and renal sodium transport. VITAMINS AND HORMONES 2019; 113:239-258. [PMID: 32138950 DOI: 10.1016/bs.vh.2019.08.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
In mammals, three subtypes of V-receptors have been identified in the kidney. The effects of vasopressin, a hormone synthesized in the hypothalamus, are triggered by three distinct receptor isoforms: V2, V1a, and V1b. Stimulation of V2-receptors regulates urine osmotic concentration by increasing sodium reabsorption in the thick ascending limb of the loop of Henle and enhancing osmotic permeability of the epithelium cells in the collecting duct. Stimulation of V1a-receptors inhibits renal sodium reabsorption and induces natriuresis, comparable to the effect of the diuretic furosemide, in the thick ascending limb of the loop of Henle. Stimulation of V1b-receptors induces potassium secretion in the final parts of the distal segments and initial parts of the collecting ducts. In this review, we discuss the role of vasopressin and its interaction with V-receptor subtypes in natriuresis and for stabilizing the physicochemical parameters of the internal environment and water-salt homeostasis in humans. A better understanding of these systems and their regulation is necessary to facilitate identification of additional system components and mechanisms, clarify their contribution during various normal and pathological functional states, and suggest novel strategies for the development of therapeutic interventions.
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Affiliation(s)
- Yu V Natochin
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia.
| | - D V Golosova
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, St. Petersburg, Russia
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Li J, He Q, Li Q, Huang R, Wei X, Pan X, Wu W. Decreased expression of Na+-H+ exchanger isoforms 1 and 3 in denervated spontaneously hypertensive rat kidney. Clin Exp Hypertens 2018; 41:235-243. [PMID: 29787310 DOI: 10.1080/10641963.2018.1469639] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Jianling Li
- Department of Cardiology, First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Qiaoling He
- Department of Pharmacology, Affiliated Hospital of Guangxi Medical University, The First people’s Hospital of Nanning, Nanning, China
| | - Qingjie Li
- Department of Cardiology, First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Rongjie Huang
- Department of Pharmacology, Affiliated Hospital of Guangxi Medical University, The First people’s Hospital of Nanning, Nanning, China
| | - Xiaoyan Wei
- Department of Pharmacology, Affiliated Hospital of Guangxi Medical University, The First people’s Hospital of Nanning, Nanning, China
| | - Xiaofeng Pan
- Department of Cardiology, First Affiliated Hospital of Guangxi Medical University, Nanning, China
| | - Weifeng Wu
- Department of Cardiology, First Affiliated Hospital of Guangxi Medical University, Nanning, China
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Watts BA, George T, Badalamenti A, Good DW. High-mobility group box 1 inhibits HCO3- absorption in the medullary thick ascending limb through RAGE-Rho-ROCK-mediated inhibition of basolateral Na+/H+ exchange. Am J Physiol Renal Physiol 2016; 311:F600-13. [PMID: 27358052 DOI: 10.1152/ajprenal.00185.2016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Accepted: 06/27/2016] [Indexed: 02/07/2023] Open
Abstract
High-mobility group box 1 (HMGB1) is a nuclear protein released extracellularly in response to infection or injury, where it activates immune responses and contributes to the pathogenesis of kidney dysfunction in sepsis and sterile inflammatory disorders. Recently, we demonstrated that HMGB1 inhibits HCO3 (-) absorption in perfused rat medullary thick ascending limbs (MTAL) through a basolateral receptor for advanced glycation end products (RAGE)-dependent pathway that is additive to Toll-like receptor 4 (TLR4)-ERK-mediated inhibition by LPS (Good DW, George T, Watts BA III. Am J Physiol Renal Physiol 309: F720-F730, 2015). Here, we examined signaling and transport mechanisms that mediate inhibition by HMGB1. Inhibition of HCO3 (-) absorption by HMGB1 was eliminated by the Rho-associated kinase (ROCK) inhibitor Y27632 and by a specific inhibitor of Rho, the major upstream activator of ROCK. HMGB1 increased RhoA and ROCK1 activity. HMGB1-induced ROCK1 activation was eliminated by the RAGE antagonist FPS-ZM1 and by inhibition of Rho. The Rho and ROCK inhibitors had no effect on inhibition of HCO3 (-) absorption by bath LPS. Inhibition of HCO3 (-) absorption by HMGB1 was eliminated by bath amiloride, 0 Na(+) bath, and the F-actin stabilizer jasplakinolide, three conditions that selectively prevent inhibition of MTAL HCO3 (-) absorption mediated through NHE1. HMGB1 decreased basolateral Na(+)/H(+) exchange activity through activation of ROCK. We conclude that HMGB1 inhibits HCO3 (-) absorption in the MTAL through a RAGE-RhoA-ROCK1 signaling pathway coupled to inhibition of NHE1. The HMGB1-RAGE-RhoA-ROCK1 pathway thus represents a potential target to attenuate MTAL dysfunction during sepsis and other inflammatory disorders. HMGB1 and LPS inhibit HCO3 (-) absorption through different receptor signaling and transport mechanisms, which enables these pathogenic mediators to act directly and independently to impair MTAL function.
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Affiliation(s)
- Bruns A Watts
- Department of Internal Medicine, The University of Texas Medical Branch, Galveston, Texas; and
| | - Thampi George
- Department of Internal Medicine, The University of Texas Medical Branch, Galveston, Texas; and
| | - Andrew Badalamenti
- Department of Internal Medicine, The University of Texas Medical Branch, Galveston, Texas; and
| | - David W Good
- Department of Internal Medicine, The University of Texas Medical Branch, Galveston, Texas; and Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, Galveston, Texas
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Abstract
The H(+) concentration in human blood is kept within very narrow limits, ~40 nmol/L, despite the fact that dietary metabolism generates acid and base loads that are added to the systemic circulation throughout the life of mammals. One of the primary functions of the kidney is to maintain the constancy of systemic acid-base chemistry. The kidney has evolved the capacity to regulate blood acidity by performing three key functions: (i) reabsorb HCO3(-) that is filtered through the glomeruli to prevent its excretion in the urine; (ii) generate a sufficient quantity of new HCO3(-) to compensate for the loss of HCO3(-) resulting from dietary metabolic H(+) loads and loss of HCO3(-) in the urea cycle; and (iii) excrete HCO3(-) (or metabolizable organic anions) following a systemic base load. The ability of the kidney to perform these functions requires that various cell types throughout the nephron respond to changes in acid-base chemistry by modulating specific ion transport and/or metabolic processes in a coordinated fashion such that the urine and renal vein chemistry is altered appropriately. The purpose of the article is to provide the interested reader with a broad review of a field that began historically ~60 years ago with whole animal studies, and has evolved to where we are currently addressing questions related to kidney acid-base regulation at the single protein structure/function level.
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Affiliation(s)
- Ira Kurtz
- Division of Nephrology, David Geffen School of Medicine, Los Angeles, CA; Brain Research Institute, UCLA, Los Angeles, CA
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8
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Good DW, George T, Watts BA. High-mobility group box 1 inhibits HCO(3)(-) absorption in medullary thick ascending limb through a basolateral receptor for advanced glycation end products pathway. Am J Physiol Renal Physiol 2015; 309:F720-30. [PMID: 26180239 DOI: 10.1152/ajprenal.00227.2015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 07/07/2015] [Indexed: 12/31/2022] Open
Abstract
High-mobility group box 1 (HMGB1) is a damage-associated molecule implicated in mediating kidney dysfunction in sepsis and sterile inflammatory disorders. HMGB1 is a nuclear protein released extracellularly in response to infection or injury, where it interacts with Toll-like receptor 4 (TLR4) and other receptors to mediate inflammation. Previously, we demonstrated that LPS inhibits HCO(3)(-) absorption in the medullary thick ascending limb (MTAL) through a basolateral TLR4-ERK pathway (Watts BA III, George T, Sherwood ER, Good DW. Am J Physiol Cell Physiol 301: C1296-C1306, 2011). Here, we examined whether HMGB1 could inhibit HCO(3)(-) absorption through the same pathway. Adding HMGB1 to the bath decreased HCO(3)(-) absorption by 24% in isolated, perfused rat and mouse MTALs. In contrast to LPS, inhibition by HMGB1 was preserved in MTALs from TLR4(-/-) mice and was unaffected by ERK inhibitors. Inhibition by HMGB1 was eliminated by the receptor for advanced glycation end products (RAGE) antagonist FPS-ZM1 and by neutralizing anti-RAGE antibody. Confocal immunofluorescence showed expression of RAGE in the basolateral membrane domain. Inhibition of HCO(3)(-) absorption by HMGB1 through RAGE was additive to inhibition by LPS through TLR4 and to inhibition by Gram-positive bacterial molecules through TLR2. Bath amiloride, which selectively prevents inhibition of MTAL HCO(3)(-) absorption mediated through Na⁺/H⁺ exchanger 1 (NHE1), eliminated inhibition by HMGB1. We conclude that HMGB1 inhibits MTAL HCO(3)(-) absorption through a RAGE-dependent pathway distinct from TLR4-mediated inhibition by LPS. These studies provide new evidence that HMGB1-RAGE signaling acts directly to impair the transport function of renal tubules. They reveal a novel paradigm for sepsis-induced renal tubule dysfunction, whereby exogenous pathogen-associated molecules and endogenous damage-associated molecules act directly and independently to inhibit MTAL HCO(3)(-) absorption through different receptor signaling pathways.
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Affiliation(s)
- David W Good
- Department of Internal Medicine, The University of Texas Medical Branch, Galveston, Texas; and Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, Galveston, Texas
| | - Thampi George
- Department of Internal Medicine, The University of Texas Medical Branch, Galveston, Texas; and
| | - Bruns A Watts
- Department of Internal Medicine, The University of Texas Medical Branch, Galveston, Texas; and
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9
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Renal acid-base regulation: new insights from animal models. Pflugers Arch 2014; 467:1623-41. [PMID: 25515081 DOI: 10.1007/s00424-014-1669-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Revised: 12/02/2014] [Accepted: 12/03/2014] [Indexed: 12/16/2022]
Abstract
Because majority of biological processes are dependent on pH, maintaining systemic acid-base balance is critical. The kidney contributes to systemic acid-base regulation, by reabsorbing HCO3 (-) (both filtered by glomeruli and generated within a nephron) and acidifying urine. Abnormalities in those processes will eventually lead to a disruption in systemic acid-base balance and provoke metabolic acid-base disorders. Research over the past 30 years advanced our understanding on cellular and molecular mechanisms responsible for those processes. In particular, a variety of transgenic animal models, where target genes are deleted either globally or conditionally, provided significant insights into how specific transporters are contributing to the renal acid-base regulation. Here, we broadly overview the mechanisms of renal ion transport participating to acid-base regulation, with emphasis on data obtained from transgenic mice models.
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10
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Nonoguchi H, Izumi Y, Nakayama Y, Matsuzaki T, Yasuoka Y, Inoue T, Inoue H, Mouri T, Kawahara K, Saito H, Tomita K. Effects of atrial natriuretic peptide on bicarbonate transport in long- and short-looped medullary thick ascending limbs of rats. PLoS One 2013; 8:e83146. [PMID: 24376658 PMCID: PMC3871552 DOI: 10.1371/journal.pone.0083146] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2013] [Accepted: 10/30/2013] [Indexed: 11/19/2022] Open
Abstract
Atrial natriuretic peptide (ANP) is known to influence NaCl transport in the medullary thick ascending limbs (MAL), where the largest NaCl reabsorption occurs among distal nephron segments in response to arginine vasopressin (AVP). In the present study, we investigated the effect of ANP on bicarbonate (HCO3−) transport in the MAL using an isolated tubule perfusion technique. The HCO3− concentration was measured using free-flow ultramicro-fluorometer. We first observed basal HCO3− reabsorption in both long- and short-looped MALs (lMALs, and sMALs, respectively). AVP inhibited HCO3− reabsorption in both lMALs and sMALs, whereas ANP did not change HCO3− transport. However, in the presence of AVP, ANP restored the HCO3− reabsorption inhibited by AVP both in lMAL and sMAL. The effects of ANP on HCO3− transport was mimicked by cyclic GMP. The mRNA expression level of the vasopressin V2 receptor in lMALs was significantly higher than in sMALs, whereas expression of the V1a receptor was unchanged. In summary, AVP inhibits HCO3− transport, and ANP counteracts the action of AVP on HCO3− transport both in lMALs and sMALs.
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Affiliation(s)
- Hiroshi Nonoguchi
- Department of Internal Medicine and Education & Research Center, Kitasato University Medical Center, Kitamoto, Saitama, Japan
- * E-mail:
| | - Yuichiro Izumi
- Systems Biology Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Yushi Nakayama
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Kumamoto, Japan
| | - Takanobu Matsuzaki
- Department of Pharmacy, Kumamoto University Hospital, Kumamoto, Kumamoto, Japan
| | - Yukiko Yasuoka
- Department of Physiology, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan
| | - Takeaki Inoue
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Kumamoto, Japan
| | - Hideki Inoue
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Kumamoto, Japan
| | - Tomohiko Mouri
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Kumamoto, Japan
| | - Katsumasa Kawahara
- Department of Physiology, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan
| | - Hideyuki Saito
- Department of Pharmacy, Kumamoto University Hospital, Kumamoto, Kumamoto, Japan
| | - Kimio Tomita
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Kumamoto, Japan
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Christensen HL, Nguyen AT, Pedersen FD, Damkier HH. Na(+) dependent acid-base transporters in the choroid plexus; insights from slc4 and slc9 gene deletion studies. Front Physiol 2013; 4:304. [PMID: 24155723 PMCID: PMC3804831 DOI: 10.3389/fphys.2013.00304] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 10/02/2013] [Indexed: 02/02/2023] Open
Abstract
The choroid plexus epithelium (CPE) is located in the ventricular system of the brain, where it secretes the majority of the cerebrospinal fluid (CSF) that fills the ventricular system and surrounds the central nervous system. The CPE is a highly vascularized single layer of cuboidal cells with an unsurpassed transepithelial water and solute transport rate. Several members of the slc4a family of bicarbonate transporters are expressed in the CPE. In the basolateral membrane the electroneutral Na+ dependent Cl−/HCO3− exchanger, NCBE (slc4a10) is expressed. In the luminal membrane, the electrogenic Na+:HCO3− cotransporter, NBCe2 (slc4a5) is expressed. The electroneutral Na+:HCO3− cotransporter, NBCn1 (slc4a7), has been located in both membranes. In addition to the bicarbonate transporters, the Na+/H+ exchanger, NHE1 (slc9a1), is located in the luminal membrane of the CPE. Genetically modified mice targeting slc4a2, slc4a5, slc4a7, slc4a10, and slc9a1 have been generated. Deletion of slc4a5, 7 or 10, or slc9a1 has numerous impacts on CP function and structure in these mice. Removal of the transporters affects brain ventricle size (slc4a5 and slc4a10) and intracellular pH regulation (slc4a7 and slc4a10). In some instances, removal of the proteins from the CPE (slc4a5, 7, and 10) causes changes in abundance and localization of non-target transporters known to be involved in pH regulation and CSF secretion. The focus of this review is to combine the insights gathered from these knockout mice to highlight the impact of slc4 gene deletion on the CSF production and intracellular pH regulation resulting from the deletion of slc4a5, 7 and 10, and slc9a1. Furthermore, the review contains a comparison of the described human mutations of these genes to the findings in the knockout studies. Finally, the future perspective of utilizing these proteins as potential targets for the treatment of CSF disorders will be discussed.
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Watts BA, George T, Good DW. Lumen LPS inhibits HCO3(-) absorption in the medullary thick ascending limb through TLR4-PI3K-Akt-mTOR-dependent inhibition of basolateral Na+/H+ exchange. Am J Physiol Renal Physiol 2013; 305:F451-62. [PMID: 23698118 DOI: 10.1152/ajprenal.00102.2013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Sepsis and endotoxemia induce defects in renal tubule function, but the mechanisms are poorly understood. Recently, we demonstrated that lipopolysaccharide (LPS) inhibits HCO3(-) absorption in the medullary thick ascending limb (MTAL) through activation of different Toll-like receptor 4 (TLR4) signaling pathways in the basolateral and apical membranes. Basolateral LPS inhibits HCO3(-) absorption through ERK-dependent inhibition of the apical Na(+)/H(+) exchanger NHE3. Here, we examined the mechanisms of inhibition by lumen LPS. Adding LPS to the lumen decreased HCO3(-) absorption by 29% in rat and mouse MTALs perfused in vitro. Inhibitors of phosphoinositide 3-kinase (PI3K) or its effectors Akt and mammalian target of rapamycin (mTOR) eliminated inhibition of HCO3(-) absorption by lumen LPS but had no effect on inhibition by bath LPS. Exposure to LPS for 15 min induced increases in phosphorylation of Akt and mTOR in microdissected MTALs that were blocked by wortmannin, consistent with activation of Akt and mTOR downstream of PI3K. The effects of lumen LPS to activate Akt and inhibit HCO3(-) absorption were eliminated in MTALs from TLR4(-/-) and MyD88(-/-) mice but preserved in tubules lacking Trif or CD14. Inhibition of HCO3(-) absorption by lumen LPS was eliminated under conditions that inhibit basolateral Na(+)/H(+) exchange and prevent inhibition of HCO3(-) absorption mediated through NHE1. Lumen LPS decreased basolateral Na(+)/H(+) exchange activity through PI3K. We conclude that lumen LPS inhibits HCO3(-) absorption in the MTAL through TLR4/MyD88-dependent activation of a PI3K-Akt-mTOR pathway coupled to inhibition of NHE1. Molecular components of the TLR4-PI3K-mTOR pathway represent potential therapeutic targets for sepsis-induced renal tubule dysfunction.
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Affiliation(s)
- Bruns A Watts
- Div. of Nephrology, 4.200 John Sealy Annex, The Univ. of Texas Medical Branch, 301 Univ. Blvd., Galveston, TX 77555-0562.
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Watts BA, George T, Sherwood ER, Good DW. A two-hit mechanism for sepsis-induced impairment of renal tubule function. Am J Physiol Renal Physiol 2013; 304:F863-74. [PMID: 23324175 DOI: 10.1152/ajprenal.00608.2012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Renal insufficiency is a common and severe complication of sepsis, and the development of kidney dysfunction increases morbidity and mortality in septic patients. Sepsis is associated with a variety of defects in renal tubule function, but the underlying mechanisms are incompletely understood. We used a cecal ligation and puncture (CLP) model to examine mechanisms by which sepsis influences the transport function of the medullary thick ascending limb (MTAL). MTALs from sham and CLP mice were studied in vitro 18 h after surgery. The results show that sepsis impairs the ability of the MTAL to absorb HCO(3)(-) through two distinct mechanisms. First, sepsis induces an adaptive decrease in the intrinsic capacity of the tubules to absorb HCO(3)(-). This effect is associated with an increase in ERK phosphorylation in MTAL cells and is prevented by pretreatment of CLP mice with a MEK/ERK inhibitor. The CLP-induced reduction in intrinsic HCO(3)(-) absorption rate appears to involve loss of function of basolateral Na(+)/H(+) exchange. Second, sepsis enhances the ability of LPS to inhibit HCO(3)(-) absorption, mediated through upregulation of Toll-like receptor 4 (TLR4)-ERK signaling in the basolateral membrane. The two inhibitory mechanisms are additive and thus can function in a two-hit capacity to impair renal tubule function in sepsis. Both effects depend on ERK and are eliminated by interventions that prevent ERK activation. Thus the TLR4 and ERK signaling pathways represent potential therapeutic targets to treat or prevent sepsis-induced renal tubule dysfunction.
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Affiliation(s)
- Bruns A Watts
- Department of Internal Medicine, University of Texas Medical Branch, Galveston, TX 77555, USA
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The potential role of ozone in ameliorating the age-related biochemical changes in male rat cerebral cortex. Biogerontology 2012; 13:565-81. [PMID: 23001537 DOI: 10.1007/s10522-012-9400-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 09/11/2012] [Indexed: 10/27/2022]
Abstract
Controlled ozone (O(3)) administration is known to promote oxidative preconditioning and, thus, may reverse chronic oxidative stress that accompanies aging. Therefore, the present work was undertaken to study the potential role of O(3) in ameliorating certain age-related biochemical changes represented by impaired activities of inner mitochondrial membrane enzymes, compromised energy production and increased oxidative burden in male rat cerebral cortex. Prophylactic administration of O(3)-O(2) mixture to 3 month-old rats, at an intrarectal dose of 0.6 mg O(3) kg(-1) body weight twice/week for 3 months then once/week until the age of 15 months, normalized reduced glutathione content, adenosine triphosphate/adenosine diphosphate ratio, mitochondrial superoxide dismutase (SOD) and complex IV (cytochrome-c oxidase) activities, improved glutathione redox index (GSHRI), complex I (NADH-ubiquinone oxidoreductase) and mitochondrial nitric oxide synthase (mtNOS) activities, and attenuated the rise in malondialdehyde (MDA) and mitochondrial protein carbonyl levels. On the other hand, therapeutic administration of the same dose of O(3)-O(2) mixture to 14 month-old rats three times/week for 1 month, reduced mitochondrial protein carbonyl level only. Other favorable effects, including normalization of Na,K-adenosine triphosphatase (Na,K-ATPase) activity and reduction in lipofuscin level in the prophylactic group, as well as improvement in mitochondrial SOD and complex I activities with a decrease in total MDA level in the therapeutic group, were comparable to the effects observed in the corresponding O(2)-treated control groups. In conclusion, the present study revealed that prophylactic administration of O(3)-O(2) mixture provided better amelioration of age-related cerebrocortical alterations by combining the advantages of both O(3) and O(2) therapies.
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Good DW, George T, Watts BA. Toll-like receptor 2 is required for LPS-induced Toll-like receptor 4 signaling and inhibition of ion transport in renal thick ascending limb. J Biol Chem 2012; 287:20208-20. [PMID: 22523073 DOI: 10.1074/jbc.m111.336255] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Previously we demonstrated that basolateral LPS inhibits HCO(3)(-) absorption in the renal medullary thick ascending limb (MTAL) through TLR4-dependent ERK activation. Here we report that the response of the MTAL to basolateral LPS requires TLR2 in addition to TLR4. The basolateral addition of LPS (ultrapure Escherichia coli K12) decreased HCO(3)(-) absorption in isolated, perfused MTALs from wild-type mice but had no effect in MTALs from TLR2(-/-) mice. In contrast, inhibition of HCO(3)(-) absorption by lumen LPS was preserved in TLR2(-/-) MTALs, indicating that TLR2 is involved specifically in mediating the basolateral LPS response. LPS also did not increase ERK phosphorylation in MTALs from TLR2(-/-) mice. TLR2 deficiency had no effect on expression of TLR4, MD-2, or MyD88. However, LPS-induced recruitment of MyD88 to the basolateral membrane was impaired in TLR2(-/-) MTALs. Inhibition of HCO(3)(-) absorption by LPS did not require CD14. Co-immunoprecipitation studies demonstrated an association between TLR4 and TLR2. Inhibition of HCO(3)(-) absorption by TLR2-specific ligands was preserved in MTALs from TLR4(-/-) mice. These results indicate that the effect of basolateral LPS to inhibit HCO(3)(-) absorption in the MTAL through MyD88-dependent ERK activation depends on a novel interaction between TLR4 and TLR2. TLR2 plays a dual role in the induction of intracellular signals that impair MTAL function, both through cooperation with TLR4 to mediate ERK signaling by LPS and through a TLR4-independent signaling pathway activated by Gram-positive bacterial ligands. Regulation of TLR2 expression and its interaction with TLR4 may provide new mechanisms for controlling and therapeutic targeting of TLR4-mediated LPS responses.
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Affiliation(s)
- David W Good
- Departments of Internal Medicine, University of Texas Medical Branch, Galveston, Texas 77555, USA.
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Boedtkjer E, Damkier HH, Aalkjaer C. NHE1 knockout reduces blood pressure and arterial media/lumen ratio with no effect on resting pH(i) in the vascular wall. J Physiol 2012; 590:1895-906. [PMID: 22351634 DOI: 10.1113/jphysiol.2011.227132] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Acid–base transport in the vascular wall remains incompletely understood. Here, we investigated (a) implications of Na(+)/H(+) exchanger NHE1 knockout for vascular smooth muscle (VSMC) and endothelial cell (EC) pH(i) regulation, mesenteric artery morphology, vasomotor function and blood pressure regulation, and (b) consequences of sustained EC and VSMC acidification for vasomotor function. Na(+)/H(+) exchange activity was abolished in VSMCs and ECs from NHE1 knockout mice, but with CO(2)/HCO(3)(−) present, steady-state pH(i) was unaffected. Active tension was 30% smaller in arteries from NHE1 knockout than wild-type mice, and media thickness equally reduced. Number of VSMCs per unit artery length was unchanged whereas volume and cross-sectional area of individual VSMCs were reduced. Media stress, force production per VSMC cross-sectional area and VSMC Ca(2+) responses were unaffected. Blood pressure was 25 mmHg lower in NHE1 knockout than wild-type mice. Omission of CO(2)/HCO(3)(−) caused VSMCs and ECs to acidify substantially more in NHE1 knockout (0.3–0.6 pH-units) than wild-type (0.02–0.1 pH units) mice. Removing CO(2)/HCO(3)(−) inhibited acetylcholine-induced NO-mediated relaxations in arteries from NHE1 knockout but not wild-type mice. Without CO(2)/HCO(3)(−), effects of NO synthase and rho kinase inhibition on noradrenaline-induced contractions were smaller in arteries from NHE1 knockout than wild-type mice whereas the EC Ca(2+) response to acetylcholine, VSMC Ca(2+) response to noradrenaline and vasorelaxation to S-nitroso-N-acetylpenicillamine were unaffected. In conclusion, NHE1 mediates the Na(+)/H(+) exchange in ECs and VSMCs. Under physiological conditions, CO(2)/HCO(3)(−)-dependent mechanisms mask the pH(i)-regulatory function of NHE1. NHE1 knockout causes hypotrophy of VSMCs, reduced artery tension and lower blood pressure. At acidic pH(i), NO-mediated vasorelaxation and rho kinase-dependent VSMC Ca(2+) sensitivity are reduced.
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Affiliation(s)
- Ebbe Boedtkjer
- Department of Biomedicine and the Water and Salt Research Center, Aarhus University, Aarhus C, Denmark.
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Watts BA, George T, Sherwood ER, Good DW. Basolateral LPS inhibits NHE3 and HCOFormula absorption through TLR4/MyD88-dependent ERK activation in medullary thick ascending limb. Am J Physiol Cell Physiol 2011; 301:C1296-306. [PMID: 21881005 DOI: 10.1152/ajpcell.00237.2011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Sepsis is associated with defects in renal tubule function, but the underlying mechanisms are incompletely understood. Recently, we demonstrated that Gram-negative bacterial lipopolysaccharide (LPS) inhibits HCO(3)(-) absorption in the medullary thick ascending limb (MTAL) through activation of Toll-like receptor 4 (TLR4). Here, we examined the mechanisms responsible for inhibition of HCO(3)(-) absorption by basolateral LPS. Adding LPS to the bath decreased HCO(3)(-) absorption by 30% in rat and mouse MTALs perfused in vitro. The inhibition of HCO(3)(-) absorption was eliminated by the mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK)/ERK inhibitors U0126 and PD98059. LPS induced a rapid (<15 min) and sustained (up to 60 min) increase in ERK phosphorylation in microdissected MTALs that was blocked by PD98059. The effects of basolateral LPS to activate ERK and inhibit HCO(3)(-) absorption were eliminated in MTALs from TLR4(-/-) and myeloid differentiation factor 88 (MyD88)(-/-) mice but were preserved in MTALs from TIR (Toll/interleukin-1 receptor) domain-containing adapter-inducing interferon-β (Trif)(-/-) mice. Basolateral LPS decreased apical Na(+)/H(+) exchanger 3 NHE3 activity through a decrease in maximal velocity (V(max)). The inhibition of NHE3 by LPS was eliminated by MEK/ERK inhibitors. LPS inhibited HCO(3)(-) absorption despite the presence of physiological stimuli that activate ERK in the MTAL. We conclude that basolateral LPS inhibits HCO(3)(-) absorption in the MTAL through activation of a TLR4/MyD88/MEK/ERK pathway coupled to inhibition of NHE3. These studies identify NHE3 as a target of TLR4 signaling in the MTAL and show that bacterial molecules can impair the absorptive functions of renal tubules through inhibition of this exchanger. The ERK pathway links TLR4 to downstream modulation of ion transport proteins and represents a potential target for treatment of sepsis-induced renal tubule dysfunction.
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Affiliation(s)
- Bruns A Watts
- Division of Nephrology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-0562, USA
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Good DW, George T, Watts BA. High sodium intake increases HCO(3)- absorption in medullary thick ascending limb through adaptations in basolateral and apical Na+/H+ exchangers. Am J Physiol Renal Physiol 2011; 301:F334-43. [PMID: 21613418 DOI: 10.1152/ajprenal.00106.2011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A high sodium intake increases the capacity of the medullary thick ascending limb (MTAL) to absorb HCO(3)(-). Here, we examined the role of the apical NHE3 and basolateral NHE1 Na(+)/H(+) exchangers in this adaptation. MTALs from rats drinking H(2)O or 0.28 M NaCl for 5-7 days were perfused in vitro. High sodium intake increased HCO(3)(-) absorption rate by 60%. The increased HCO(3)(-) absorptive capacity was mediated by an increase in apical NHE3 activity. Inhibiting basolateral NHE1 with bath amiloride eliminated 60% of the adaptive increase in HCO(3)(-) absorption. Thus the majority of the increase in NHE3 activity was dependent on NHE1. A high sodium intake increased basolateral Na(+)/H(+) exchange activity by 89% in association with an increase in NHE1 expression. High sodium intake increased apical Na(+)/H(+) exchange activity by 30% under conditions in which basolateral Na(+)/H(+) exchange was inhibited but did not change NHE3 abundance. These results suggest that high sodium intake increases HCO(3)(-) absorptive capacity in the MTAL through 1) an adaptive increase in basolateral NHE1 activity that results secondarily in an increase in apical NHE3 activity; and 2) an adaptive increase in NHE3 activity, independent of NHE1 activity. These studies support a role for NHE1 in the long-term regulation of renal tubule function and suggest that the regulatory interaction whereby NHE1 enhances the activity of NHE3 in the MTAL plays a role in the chronic regulation of HCO(3)(-) absorption. The adaptive increases in Na(+)/H(+) exchange activity and HCO(3)(-) absorption in the MTAL may play a role in enabling the kidneys to regulate acid-base balance during changes in sodium and volume balance.
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Affiliation(s)
- David W Good
- Departments of Internal Medicine, The University of Texas Medical Branch, Galveston, Texas 77555-0562, USA.
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19
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Fenton RA, Praetorius J. Molecular Physiology of the Medullary Collecting Duct. Compr Physiol 2011; 1:1031-56. [DOI: 10.1002/cphy.c100064] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Good DW, George T, Watts BA. Toll-like receptor 2 mediates inhibition of HCO(3)(-) absorption by bacterial lipoprotein in medullary thick ascending limb. Am J Physiol Renal Physiol 2010; 299:F536-44. [PMID: 20554644 DOI: 10.1152/ajprenal.00108.2010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Bacterial infection and sepsis are associated with renal tubule dysfunction and dysregulation of systemic electrolyte balance but the underlying mechanisms are incompletely understood. Recently, we demonstrated that HCO(3)(-) absorption by the medullary thick ascending limb (MTAL) is inhibited by gram-negative bacterial LPS through activation of Toll-like receptor 4 (TLR4). Here, we examined whether MTAL transport is altered by activation of TLR2, the receptor predominantly responsible for recognizing gram-positive bacteria. Confocal immunofluorescence showed expression of TLR2 in the basolateral membrane domain of rat and mouse MTALs. The functional role of TLR2 was examined in perfused MTALs using Pam(3)CSK(4), a bacterial lipoprotein analog that specifically activates TLR2. Adding Pam(3)CSK(4) to the bath decreased HCO(3)(-) absorption by 25%. The inhibition by Pam(3)CSK(4) was eliminated in MTALs from TLR2(-/-) mice. HCO(3)(-) absorption was also inhibited by the TLR2 agonists lipoteichoic acid and peptidoglycan, two cell wall components of gram-positive bacteria. The MEK/ERK inhibitor U0126 eliminated inhibition of HCO(3)(-) absorption by bath LPS but had no effect on inhibition by Pam(3)CSK(4). The inhibition by Pam(3)CSK(4) was eliminated by the protein kinase C inhibitors chelerythrine Cl and bisindolylmaleimide. Moreover, the inhibition by Pam(3)CSK(4), lipoteichoic acid, and peptidoglycan was additive to inhibition by LPS. Thus, agonists of basolateral TLR2 and TLR4 inhibit HCO(3)(-) absorption independently through distinct signaling pathways. We conclude that bacterial components act directly through TLRs to modify the transport function of renal tubules. During polymicrobial sepsis, gram-positive bacterial molecules acting through TLR2 and gram-negative LPS acting through TLR4 can function through parallel signaling pathways to impair MTAL transport. The inhibition of luminal acidification may impair the ability of the kidneys to correct systemic acidosis that contributes to sepsis pathogenesis.
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Affiliation(s)
- David W Good
- Department of Internal Medicine, The University of Texas Medical Branch, Galveston, 77555-0562, USA.
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Riccardi D, Brown EM. Physiology and pathophysiology of the calcium-sensing receptor in the kidney. Am J Physiol Renal Physiol 2010; 298:F485-99. [PMID: 19923405 PMCID: PMC2838589 DOI: 10.1152/ajprenal.00608.2009] [Citation(s) in RCA: 227] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Accepted: 11/13/2009] [Indexed: 12/21/2022] Open
Abstract
The extracellular calcium-sensing receptor (CaSR) plays a major role in the maintenance of a physiological serum ionized calcium (Ca2+) concentration by regulating the circulating levels of parathyroid hormone. It was molecularly identified in 1993 by Brown et al. in the laboratory of Dr. Steven Hebert with an expression cloning strategy. Subsequent studies have demonstrated that the CaSR is highly expressed in the kidney, where it is capable of integrating signals deriving from the tubular fluid and/or the interstitial plasma. Additional studies elucidating inherited and acquired mutations in the CaSR gene, the existence of activating and inactivating autoantibodies, and genetic polymorphisms of the CaSR have greatly enhanced our understanding of the role of the CaSR in mineral ion metabolism. Allosteric modulators of the CaSR are the first drugs in their class to become available for clinical use and have been shown to treat successfully hyperparathyroidism secondary to advanced renal failure. In addition, preclinical and clinical studies suggest the possibility of using such compounds in various forms of hypercalcemic hyperparathyroidism, such as primary and lithium-induced hyperparathyroidism and that occurring after renal transplantation. This review addresses the role of the CaSR in kidney physiology and pathophysiology as well as current and in-the-pipeline treatments utilizing CaSR-based therapeutics.
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Affiliation(s)
- Daniela Riccardi
- School of Biosciences, Cardiff University, Cardiff, United Kingdom.
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Good DW, George T, Watts BA. Lipopolysaccharide directly alters renal tubule transport through distinct TLR4-dependent pathways in basolateral and apical membranes. Am J Physiol Renal Physiol 2009; 297:F866-74. [PMID: 19625374 DOI: 10.1152/ajprenal.00335.2009] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Bacterial infection of the kidney is associated with renal tubule dysfunction and dysregulation of systemic electrolyte balance. Whether bacterial molecules directly affect renal tubule transport is unknown. We examined the effects of LPS on HCO3(-) absorption in the isolated rat and mouse medullary thick ascending limb (MTAL). LPS decreased HCO3(-) absorption when added to bath or lumen. The MEK/ERK inhibitor U0126 eliminated inhibition by bath LPS but had no effect on inhibition by lumen LPS. Conversely, the mammalian target of rapamycin (mTOR) inhibitor rapamycin eliminated inhibition by lumen LPS but had no effect on inhibition by bath LPS. Inhibiting basolateral Na(+)/H(+) exchange with amiloride eliminated inhibition of HCO3(-) absorption by lumen but not bath LPS. Confocal immunofluorescence showed expression of TLR4 in basolateral and apical membrane domains. Inhibition of HCO3(-) absorption by bath and lumen LPS was eliminated in MTALs from TLR4(-/-) mice. Thus LPS inhibits HCO3(-) absorption through distinct TLR4-dependent pathways in basolateral and apical membranes. These results establish that bacterial molecules can directly impair the transport function of renal tubules, identifying a new mechanism contributing to tubule dysfunction during bacterial infection. The LPS-induced reduction in luminal acidification may contribute to Gram-negative pathogenicity by promoting bacterial adherence and growth and impairing correction of infection-induced systemic acid-base disorders.
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Affiliation(s)
- David W Good
- Div. of Nephrology, 4.200 John Sealy Annex, The Univ. of Texas Medical Branch, 301 Univ. Blvd., Galveston, TX 77555-0562, USA.
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Haak JL, Buettner GR, Spitz DR, Kregel KC. Aging augments mitochondrial susceptibility to heat stress. Am J Physiol Regul Integr Comp Physiol 2009; 296:R812-20. [PMID: 19144753 DOI: 10.1152/ajpregu.90708.2008] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The pathophysiology of aging is accompanied by a decline in tolerance to environmental stress. While mitochondria are primary suspects in the etiology of aging, little is known about their ability to tolerate perturbations to homeostasis in older organisms. To investigate the role of mitochondria in the increased susceptibility to heat stress that accompanies aging, young and old Fischer 344 rats underwent a heat stress protocol known to elicit exaggerated cellular damage with aging. At either 2 or 24 h after heat stress, livers were removed from animals, and hepatic mitochondria were isolated. Electron microscopy revealed extensive morphological damage to mitochondria from young and, to a greater extent, old rats after heat stress. There was also a significant loss of cytochrome c from old, but not young, mitochondria and a persistent increase in 4-hydroxynonenal-modified proteins in old vs. young mitochondria exposed to heat stress. Electron paramagnetic resonance measurements of superoxide indicate greater superoxide production from mitochondria of old compared with young animals and suggest that mitochondrial integrity was altered during heat stress. The mitochondrial stress response, which functions to correct stress-induced damage to mitochondrial proteins, was also blunted in old rats. Delayed and reduced levels of heat shock protein 60 (Hsp60), the main inducible mitochondrial stress protein, were observed in old compared with young mitochondria after heat stress. Additionally, the amount of Hsp10 protein increased in young, but not old, rat liver mitochondria after hyperthermic challenge. Taken together, these data suggest that mitochondria in old animals are more vulnerable to incurring and less able to repair oxidative damage that occurs in response to a physiologically relevant heat stress.
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Affiliation(s)
- Jodie L Haak
- Dept. of Integrative Physiology, The Univ. of Iowa, Iowa City, 52242, USA
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Good DW, George T, Watts BA. Nerve growth factor inhibits Na+/H+ exchange and formula absorption through parallel phosphatidylinositol 3-kinase-mTOR and ERK pathways in thick ascending limb. J Biol Chem 2008; 283:26602-11. [PMID: 18660503 DOI: 10.1074/jbc.m803019200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In the medullary thick ascending limb, inhibiting the basolateral NHE1 Na(+)/H(+) exchanger with nerve growth factor (NGF) induces actin cytoskeleton remodeling that secondarily inhibits apical NHE3 and transepithelial HCO(3)(-) absorption. The inhibition by NGF is mediated 50% through activation of extracellular signal-regulated kinase (ERK). Here we examined the signaling pathway responsible for the remainder of the NGF-induced inhibition. Inhibition of HCO(3)(-) absorption was reduced 45% by the phosphatidylinositol 3-kinase (PI3K) inhibitors wortmannin or LY294002 and 50% by rapamycin, a specific inhibitor of mammalian target of rapamycin (mTOR), a downstream effector of PI3K. The combination of a PI3K inhibitor plus rapamycin did not cause a further reduction in the inhibition by NGF. In contrast, the combination of a PI3K inhibitor plus the MEK/ERK inhibitor U0126 completely eliminated inhibition by NGF. Rapamycin decreased NGF-induced inhibition of basolateral NHE1 by 45%. NGF induced a 2-fold increase in phosphorylation of Akt, a PI3K target linked to mTOR activation, and a 2.2-fold increase in the activity of p70 S6 kinase, a downstream effector of mTOR. p70 S6 kinase activation was blocked by wortmannin and rapamycin, consistent with PI3K, mTOR, and p70 S6 kinase in a linear pathway. Rapamycin-sensitive inhibition of NHE1 by NGF was associated with an increased level of phosphorylated mTOR in the basolateral membrane domain. These findings indicate that NGF inhibits HCO(3)(-) absorption in the medullary thick ascending limb through the parallel activation of PI3K-mTOR and ERK signaling pathways, which converge to inhibit NHE1. The results identify a role for mTOR in the regulation of Na(+)/H(+) exchange activity and implicate NHE1 as a possible downstream effector contributing to mTOR's effects on cell growth, proliferation, survival, and tumorigenesis.
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Affiliation(s)
- David W Good
- Departments of Medicine, The University of Texas Medical Branch, Galveston, Texas 77555, USA.
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Navarro A, López-Cepero JM, Bández MJ, Sánchez-Pino MJ, Gómez C, Cadenas E, Boveris A. Hippocampal mitochondrial dysfunction in rat aging. Am J Physiol Regul Integr Comp Physiol 2007; 294:R501-9. [PMID: 18077512 DOI: 10.1152/ajpregu.00492.2007] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Hippocampus mitochondrial dysfunction with impaired electron transfer and increased oxidative damage was observed upon rat aging. Hippocampal mitochondria of aged (12 mo) and senescent (20 mo) rats showed, compared with young (4 mo) rats, marked decreases in the rate of state 3 respiration with NAD-dependent substrates (32-51%) and in the activities of mitochondrial complexes I (57-73%) and IV (33-54%). The activity of mitochondrial nitric oxide synthase was also decreased, 53-66%, with age. These losses in enzymatic activity were more marked in the hippocampus than in brain cortex or in whole brain. The histochemical assay of mitochondrial complex IV in the hippocampus showed decreased staining upon aging. Oxidative damage, determined as the mitochondrial content of thiobarbituric-acid reactive substances (TBARS) and protein carbonyls, increased in aged and senescent hippocampus (66-74% in TBARS and 48-96% in carbonyls). A significant statistical correlation was observed between mitochondrial oxidative damage and enzymatic activity. Mitochondrial dysfunction with shortage of energy supply is considered a likely cause of dysfunction in aged hippocampus.
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Affiliation(s)
- Ana Navarro
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Plaza Fragela 9, 11003-Cádiz, Spain.
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Fenton RA, Knepper MA. Mouse models and the urinary concentrating mechanism in the new millennium. Physiol Rev 2007; 87:1083-112. [PMID: 17928581 DOI: 10.1152/physrev.00053.2006] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Our understanding of urinary concentrating and diluting mechanisms at the end of the 20th century was based largely on data from renal micropuncture studies, isolated perfused tubule studies, tissue analysis studies and anatomical studies, combined with mathematical modeling. Despite extensive data, several key questions remained to be answered. With the advent of the 21st century, a new approach, transgenic and knockout mouse technology, is providing critical new information about urinary concentrating processes. The central goal of this review is to summarize findings in transgenic and knockout mice pertinent to our understanding of the urinary concentrating mechanism, focusing chiefly on mice in which expression of specific renal transporters or receptors has been deleted. These include the major renal water channels (aquaporins), urea transporters, ion transporters and channels (NHE3, NKCC2, NCC, ENaC, ROMK, ClC-K1), G protein-coupled receptors (type 2 vasopressin receptor, prostaglandin receptors, endothelin receptors, angiotensin II receptors), and signaling molecules. These studies shed new light on several key questions concerning the urinary concentrating mechanism including: 1) elucidation of the role of water absorption from the descending limb of Henle in countercurrent multiplication, 2) an evaluation of the feasibility of the passive model of Kokko-Rector and Stephenson, 3) explication of the role of inner medullary collecting duct urea transport in water conservation, 4) an evaluation of the role of tubuloglomerular feedback in maintenance of appropriate distal delivery rates for effective regulation of urinary water excretion, and 5) elucidation of the importance of water reabsorption in the connecting tubule versus the collecting duct for maintenance of water balance.
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Affiliation(s)
- Robert A Fenton
- Water and Salt Research Center, Institute of Anatomy, University of Aarhus, Aarhus, Denmark.
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Abstract
NHE3 is the brush-border (BB) Na+/H+exchanger of small intestine, colon, and renal proximal tubule which is involved in large amounts of neutral Na+absorption. NHE3 is a highly regulated transporter, being both stimulated and inhibited by signaling that mimics the postprandial state. It also undergoes downregulation in diarrheal diseases as well as changes in renal disorders. For this regulation, NHE3 exists in large, multiprotein complexes in which it associates with at least nine other proteins. This review deals with short-term regulation of NHE3 and the identity and function of its recognized interacting partners and the multiprotein complexes in which NHE3 functions.
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Affiliation(s)
- Mark Donowitz
- Department of Medicine, GI Division, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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Wang D, Hu J, Bobulescu IA, Quill TA, McLeroy P, Moe OW, Garbers DL. A sperm-specific Na+/H+ exchanger (sNHE) is critical for expression and in vivo bicarbonate regulation of the soluble adenylyl cyclase (sAC). Proc Natl Acad Sci U S A 2007; 104:9325-30. [PMID: 17517652 PMCID: PMC1890493 DOI: 10.1073/pnas.0611296104] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Indexed: 02/04/2023] Open
Abstract
We previously identified a sperm-specific Na(+)/H(+) exchanger (sNHE) principally localized to the flagellum. Disruption of the sNHE gene in mice resulted in absolute male infertility associated with a complete loss of sperm motility. Here, we show that the sNHE-null spermatozoa fail to develop the cAMP-dependent protein tyrosine phosphorylation that coincides with the functional maturation occurring upon incubation in capacitating conditions in vitro. Both the sperm motility defect and the lack of induced protein tyrosine phosphorylation are rescued by the addition of cell-permeable cAMP analogs, suggesting that cAMP metabolism is impaired in spermatozoa lacking sNHE. Our analyses of the bicarbonate-dependent soluble adenylyl cyclase (sAC) signaling pathway in sNHE-null sperm cells reveal that sNHE is required for the expression of full-length sAC, and that it is important for the bicarbonate stimulation of sAC activity in spermatozoa. Furthermore, both codependent expression and coimmunoprecipitation experiments indicate that sNHE and sAC associate with each other. Thus, these two proteins appear to be components of a signaling complex at the sperm flagellar plasma membrane. We propose that the formation of this complex efficiently modulates intracellular pH and bicarbonate levels through the rapid and effective control of sAC and sNHE activities to facilitate sperm motility regulation.
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Affiliation(s)
- Dan Wang
- Cecil H. and Ida Green Center for Reproductive Biology Sciences, Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390-9051, USA.
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Affiliation(s)
- David W Good
- Department of Medicine, University of Texas Medical Branch, Galveston 77555-0562, USA.
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Navarro A, Boveris A. The mitochondrial energy transduction system and the aging process. Am J Physiol Cell Physiol 2006; 292:C670-86. [PMID: 17020935 DOI: 10.1152/ajpcell.00213.2006] [Citation(s) in RCA: 476] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Aged mammalian tissues show a decreased capacity to produce ATP by oxidative phosphorylation due to dysfunctional mitochondria. The mitochondrial content of rat brain and liver is not reduced in aging and the impairment of mitochondrial function is due to decreased rates of electron transfer by the selectively diminished activities of complexes I and IV. Inner membrane H(+) impermeability and F(1)-ATP synthase activity are only slightly affected by aging. Dysfunctional mitochondria in aged rodents are characterized, besides decreased electron transfer and O(2) uptake, by an increased content of oxidation products of phospholipids, proteins and DNA, a decreased membrane potential, and increased size and fragility. Free radical-mediated oxidations are determining factors of mitochondrial dysfunction and turnover, cell apoptosis, tissue function, and lifespan. Inner membrane enzyme activities, such as those of complexes I and IV and mitochondrial nitric oxide synthase, decrease upon aging and afford aging markers. The activities of these three enzymes in mice brain are linearly correlated with neurological performance, as determined by the tightrope and the T-maze tests. The same enzymatic activities correlated positively with mice survival and negatively with the mitochondrial content of lipid and protein oxidation products. Conditions that increase survival, as vitamin E dietary supplementation, caloric restriction, high spontaneous neurological activity, and moderate physical exercise, ameliorate mitochondrial dysfunction in aged brain and liver. The pleiotropic signaling of mitochondrial H(2)O(2) and nitric oxide diffusion to the cytosol seems modified in aged animals and to contribute to the decreased mitochondrial biogenesis in old animals.
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Affiliation(s)
- Ana Navarro
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Plaza Fragela 9, 11003 Cádiz, Spain.
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31
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Abstract
The kidney plays key roles in extracellular fluid pH homeostasis by reclaiming bicarbonate (HCO(3)(-)) filtered at the glomerulus and generating the consumed HCO(3)(-) by secreting protons (H(+)) into the urine (renal acidification). Sodium-proton exchangers (NHEs) are ubiquitous transmembrane proteins mediating the countertransport of Na(+) and H(+) across lipid bilayers. In mammals, NHEs participate in the regulation of cell pH, volume, and intracellular sodium concentration, as well as in transepithelial ion transport. Five of the 10 isoforms (NHE1-4 and NHE8) are expressed at the plasma membrane of renal epithelial cells. The best-studied isoform for acid-base homeostasis is NHE3, which mediates both HCO(3)(-) absorption and H(+) excretion in the renal tubule. This article reviews some important aspects of NHEs in the kidney, with special emphasis on the role of renal NHE3 in the maintenance of acid-base balance.
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Affiliation(s)
- I Alexandru Bobulescu
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
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Kregel KC, Zhang HJ. An integrated view of oxidative stress in aging: basic mechanisms, functional effects, and pathological considerations. Am J Physiol Regul Integr Comp Physiol 2006; 292:R18-36. [PMID: 16917020 DOI: 10.1152/ajpregu.00327.2006] [Citation(s) in RCA: 533] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Aging is an inherently complex process that is manifested within an organism at genetic, molecular, cellular, organ, and system levels. Although the fundamental mechanisms are still poorly understood, a growing body of evidence points toward reactive oxygen species (ROS) as one of the primary determinants of aging. The "oxidative stress theory" holds that a progressive and irreversible accumulation of oxidative damage caused by ROS impacts on critical aspects of the aging process and contributes to impaired physiological function, increased incidence of disease, and a reduction in life span. While compelling correlative data have been generated to support the oxidative stress theory, a direct cause-and-effect relationship between the accumulation of oxidatively mediated damage and aging has not been strongly established. The goal of this minireview is to broadly describe mechanisms of in vivo ROS generation, examine the potential impact of ROS and oxidative damage on cellular function, and evaluate how these responses change with aging in physiologically relevant situations. In addition, the mounting genetic evidence that links oxidative stress to aging is discussed, as well as the potential challenges and benefits associated with the development of anti-aging interventions and therapies.
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Affiliation(s)
- Kevin C Kregel
- Department of Integrative Physiology and Free Radical and Radiation Biology Program, Department of Radiation Oncology, The University of Iowa, Iowa City, IA 52242, USA.
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Abstract
Successful natural reproduction normally requires vigorously motile spermatozoa. Using a signal peptide trapping strategy, we identified two new genes, a putative sperm Na+/H+ exchanger (sNHE) and the putative cation channel CatSper2, with unique and essential roles in sperm motility. Disruption of the sNHE or CatSper2 genes in mice caused male infertility due to immotile spermatozoa or failed motility hyperactivation, respectively, without other apparent abnormalities. The immotility phenotype of the sNHE null spermatozoa appears to result from an intimate association of sNHE and the atypical adenylyl cyclase (sAC), while a failure of calcium entry requiring an apparent CatSper1 and -2 heteromeric ion channel correlates with a hyperactivation defect in these null animals. The specific expression of sNHE and the CatSpers in spermatozoa and their required function in cell motility make them excellent potential targets for the development of novel male contraceptives.
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Affiliation(s)
- Timothy A Quill
- Cecil H. and Ida Green Center for Reproductive Biology Sciences, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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Bobulescu IA, Di Sole F, Moe OW. Na+/H+ exchangers: physiology and link to hypertension and organ ischemia. Curr Opin Nephrol Hypertens 2005; 14:485-94. [PMID: 16046909 PMCID: PMC2861558 DOI: 10.1097/01.mnh.0000174146.52915.5d] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW Na/H exchangers (NHEs) are ubiquitous proteins with a very wide array of physiological functions, and they are summarized in this paper in view of the most recent advances. Hypertension and organ ischemia are two disease states of paramount importance in which NHEs have been implicated. The involvement of NHEs in the pathophysiology of these disorders is incompletely understood. This paper reviews the principal findings and current hypotheses linking NHE dysfunction to hypertension and ischemia. RECENT FINDINGS With the advent of large-scale sequencing projects and powerful in-silico analyses, we have come to know what is most likely the entire mammalian NHE gene family. Recent advances have detailed the roles of NHE proteins, exploring new functions such as anchoring, scaffolding and pH regulation of intracellular compartments. Studies of NHEs in disease models, even though not conclusive to date, have contributed new evidence on the interplay of ion transporters and the delicate ion balances that may become disrupted. SUMMARY This paper provides the interested reader with a concise overview of NHE physiology, and aims to address the implication of NHEs in the pathophysiology of hypertension and organ ischemia in light of the most recent literature.
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Affiliation(s)
- I. Alexandru Bobulescu
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research and Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Francesca Di Sole
- Institute for Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne, UK
| | - Orson W. Moe
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research and Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
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Cahill A, Hershman S, Davies A, Sykora P. Ethanol feeding enhances age-related deterioration of the rat hepatic mitochondrion. Am J Physiol Gastrointest Liver Physiol 2005; 289:G1115-23. [PMID: 16020655 PMCID: PMC1634830 DOI: 10.1152/ajpgi.00193.2005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Chronic ethanol feeding damages the hepatic mitochondrion by increasing mitochondrial DNA (mtDNA) oxidation, lowering mtDNA yields and impairing mitochondrial respiration. These effects are also seen during aging. By employing a 21-day chronic feeding regimen, we investigated the effects of ethanol consumption on mtDNA content and mitochondrial respiration in 2-, 12-, and 24-mo-old male rats. Aging resulted in decreased mtDNA content, increased mtDNA damage (as indicated by inhibition of Taq polymerase progression), and a decline in state 3 respiration; effects that were further exacerbated by ethanol feeding. Additionally, ethanol consumption caused an increase in the levels of citrate synthase while not impacting mitochondrial protein content. In conclusion, ethanol and aging combine to cause deterioration in the structural and functional integrity of the hepatic mitochondrion. The additive effects of aging and ethanol feeding may have serious consequences for hepatic energy metabolism in aged animals, and their detrimental combination may serve as one of the molecular mechanisms underlying the progression of alcoholic liver disease.
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Affiliation(s)
- Alan Cahill
- Dept. of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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Navarro A, Torrejón R, Bández MJ, López-Cepero JM, Boveris A. Mitochondrial function and mitochondria-induced apoptosis in an overstimulated rat ovarian cycle. Am J Physiol Endocrinol Metab 2005; 289:E1101-9. [PMID: 16014352 DOI: 10.1152/ajpendo.00223.2005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Female rats were treated with FSH (40 IU/kg) on the first and second diestrus days (D1 and D2) and with LH (40 IU/kg) on the proestrus (P) day to synchronize and maximize ovarian changes. Follicle area increased by 50% from D1 to P, and the estrus (E) phase showed multiple corpora lutea and massive apoptosis. Increased oxygen uptakes (42-102%) were determined in ovary slices and in isolated mitochondria in active state 3 along the proliferation phase (D1-D2-P) that returned to initial values in the E phase. Mitochondrial content and the electron transfer activities of complexes I and IV were also maximal in the P phase (20-79% higher than in D1). Production of NO by mitochondrial nitric oxide synthase (mtNOS), biochemically determined, and the mtNOS functional activity in regulating state 3 oxygen uptake were also maximal at P and 79-88% higher than at D1. The moderately increased rate of NO in the proliferative phase is associated with mitochondrial biogenesis, whereas the high rate of NO generation by mtNOS at phase P appears to trigger mitochondria-dependent apoptosis. The calculated fraction of ovary mitochondria in state 3 was at a minimal value at the P phase. Mitochondrial oxidative damage, with increased thiobarbituric acid-reactive substances and protein carbonyls, indicates progressive mitochondrial dysfunction between phases P and E. The roles of mitochondria as ATP provider, as a source of NO to signal for mitochondrial proliferation and mitochondria-dependent apoptosis, and as a source of O(2)(-) and H(2)O(2) appear well adapted to serve the proliferation-apoptosis sequence of the ovarian cycle.
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Affiliation(s)
- Ana Navarro
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, University Hospital of Puerto Real, Plaza Fragela 9, 11003 Cádiz, Spain.
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Navarro A, Gómez C, Sánchez-Pino MJ, González H, Bández MJ, Boveris AD, Boveris A. Vitamin E at high doses improves survival, neurological performance, and brain mitochondrial function in aging male mice. Am J Physiol Regul Integr Comp Physiol 2005; 289:R1392-9. [PMID: 16020519 DOI: 10.1152/ajpregu.00834.2004] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Male mice receiving vitamin E (5.0 g α-tocopherol acetate/kg of food) from 28 wk of age showed a 40% increased median life span, from 61 ± 4 wk to 85 ± 4 wk, and 17% increased maximal life span, whereas female mice equally supplemented exhibited only 14% increased median life span. The α-tocopherol content of brain and liver was 2.5-times and 7-times increased in male mice, respectively. Vitamin E-supplemented male mice showed a better performance in the tightrope (neuromuscular function) and the T-maze (exploratory activity) tests with improvements of 9–24% at 52 wk and of 28–45% at 78 wk. The rates of electron transfer in brain mitochondria, determined as state 3 oxygen uptake and as NADH-cytochrome c reductase and cytochrome oxidase activities, were 16–25% and 35–38% diminished at 52–78 wk. These losses of mitochondrial function were ameliorated by vitamin E supplementation by 37–56% and by 60–66% at the two time points considered. The activities of mitochondrial nitric oxide synthase and Mn-SOD decreased 28–67% upon aging and these effects were partially (41–68%) prevented by vitamin E treatment. Liver mitochondrial activities showed similar effects of aging and of vitamin E supplementation, although less marked. Brain mitochondrial enzymatic activities correlated negatively with the mitochondrial content of protein and lipid oxidation products ( r2= 0.58–0.99, P < 0.01), and the rates of respiration and of complex I and IV activities correlated positively ( r2= 0.74–0.80, P < 0.01) with success in the behavioral tests and with maximal life span.
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Affiliation(s)
- Ana Navarro
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Cádiz, Spain.
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Good DW, George T, Watts BA. Nongenomic regulation by aldosterone of the epithelial NHE3 Na(+)/H(+) exchanger. Am J Physiol Cell Physiol 2005; 290:C757-63. [PMID: 16251474 DOI: 10.1152/ajpcell.00391.2005] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The relevance of nongenomic pathways to regulation of epithelial function by aldosterone is poorly understood. Recently, we demonstrated that aldosterone inhibits transepithelial HCO(3)(-) absorption in the renal medullary thick ascending limb (MTAL) through a nongenomic pathway. Here, we examined the transport mechanism(s) responsible for this regulation, focusing on Na(+)/H(+) exchangers (NHE). In the MTAL, apical NHE3 mediates H(+) secretion necessary for HCO(3)(-) absorption; basolateral NHE1 influences HCO(3)(-) absorption by regulating apical NHE3 activity. In microperfused rat MTALs, the addition of 1 nM aldosterone rapidly decreased HCO(3)(-) absorption by 30%. This inhibition was unaffected by three maneuvers that inhibit basolateral Na(+)/H(+) exchange and was preserved in MTALs from NHE1 knockout mice, ruling out the involvement of NHE1. In contrast, exposure to aldosterone for 15 min caused a 30% decrease in apical Na(+)/H(+) exchange activity over the intracellular pH range from 6.5 to 7.7, due to a decrease in V(max). Inhibition of HCO(3)(-) absorption by aldosterone was not affected by 0.1 mM lumen Zn(2+) or 1 mM lumen DIDS, arguing against the involvement of an apical H(+) conductance or apical K(+)-HCO(3)(-) cotransport. These results demonstrate that aldosterone inhibits HCO(3)(-) absorption in the MTAL through inhibition of apical NHE3, and identify NHE3 as a target for nongenomic regulation by aldosterone. Aldosterone may influence a broad range of epithelial transport functions important for extracellular fluid volume and acid-base homeostasis through direct regulation of this exchanger.
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Affiliation(s)
- David W Good
- 4.200 John Sealy Annex, The University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-0562, USA.
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Navarro A, Boveris A. Hypoxia exacerbates macrophage mitochondrial damage in endotoxic shock. Am J Physiol Regul Integr Comp Physiol 2005; 288:R354-5. [PMID: 15637172 DOI: 10.1152/ajpregu.00726.2004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Zaobornyj T, Valdez LB, La Padula P, Costa LE, Boveris A. Effect of sustained hypobaric hypoxia during maturation and aging on rat myocardium. II. mtNOS activity. J Appl Physiol (1985) 2005; 98:2370-5. [PMID: 15705730 DOI: 10.1152/japplphysiol.00986.2004] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Mitochondrial nitric oxide (NO) production was assayed in rats submitted to hypobaric hypoxia and in normoxic controls (53.8 and 101.3 kPa air pressure, respectively). Heart mitochondria from young normoxic animals produced 0.62 and 0.37 nmol NO.min(-1).mg protein(-1) in metabolic states 4 and 3, respectively. This production accounts for a release to the cytosol of 29 nmol NO.min(-1).g heart(-1) and for 55% of the NO generation. The mitochondrial NO synthase (mtNOS) activity measured in submitochondrial membranes at pH 7.4 was 0.69 nmol NO.min(-1).mg protein(-1). Rats exposed to hypobaric hypoxia for 2-18 mo showed 20-60% increased left ventricle mtNOS activity compared with their normoxic siblings. Left ventricle NADH-cytochrome-c reductase and cytochrome oxidase activities decreased by 36 and 12%, respectively, from 2 to 18 mo of age, but they were not affected by hypoxia. mtNOS upregulation in hypoxia was associated with a retardation of the decline in the mechanical activity of papillary muscle upon aging and an improved recovery after anoxia-reoxygenation. The correlation of left ventricle mtNOS activity with papillary muscle contractility (determined as developed tension, maximal rates of contraction and relaxation) showed an optimal mtNOS activity (0.69 nmol.min(-1).mg protein(-1)). Heart mtNOS activity is regulated by O(2) in the inspired air and seems to play a role in NO-mediated signaling and myocardial contractility.
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Affiliation(s)
- Tamara Zaobornyj
- Fisicoquímica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina.
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Bailey MA, Giebisch G, Abbiati T, Aronson PS, Gawenis LR, Shull GE, Wang T. NHE2-mediated bicarbonate reabsorption in the distal tubule of NHE3 null mice. J Physiol 2004; 561:765-75. [PMID: 15604231 PMCID: PMC1665379 DOI: 10.1113/jphysiol.2004.074716] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2004] [Accepted: 10/06/2004] [Indexed: 12/16/2022] Open
Abstract
NHE3(-/-) mice display a profound defect in proximal tubule bicarbonate reabsorption but are only mildly acidotic owing to reduced glomerular filtration rate and enhanced H(+) secretion in distal nephron segments. In vivo microperfusion of rat distal tubules suggests that a significant fraction of bicarbonate reabsorption in this nephron segment is mediated by NHE2. Two approaches were used to evaluate the role of distal tubule NHE2 in compensating for the proximal defect of H(+) secretion in NHE3(-/-) mice. First, renal clearance experiments were used to assess the impact of HOE694, an inhibitor with significant affinity for NHE2, on excretion of bicarbonate in NHE3(-/-) and NHE2(-/-) mice. Second, in vivo micropuncture and microperfusion were employed to measure the concentration of bicarbonate in early distal tubule fluid and to measure distal bicarbonate reabsorption during a constant bicarbonate load. Our data show that HOE694 had no effect on urinary bicarbonate excretion in NHE3(+/+) mice, whereas bicarbonate excretion was higher in NHE3(-/-) mice receiving HOE694. HOE694 induced a significant increase in bicarbonate excretion in mice given an acute bicarbonate load, but there was no effect during metabolic acidosis. Bicarbonate excretion was not affected by HOE694 in bicarbonate-loaded NHE2(-/-) mice. In vivo micropuncture revealed that early distal bicarbonate concentration was elevated in both bicarbonate-loaded and NHE3(-/-) mice. Further, microperfusion experiments showed that HOE694-sensitive bicarbonate reabsorption capacity was higher in acidotic and NHE3 null animals. We conclude that NHE2 contributes importantly to acidification in the distal tubule, and that it plays a major role in limiting urinary bicarbonate losses in states in which a high luminal bicarbonate load is presented to the distal tubule, such as in NHE3 null mice.
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Affiliation(s)
- Matthew A Bailey
- Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
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