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Huang YC, Liu CJ, Lu ZH, Huang HS. Long-Term Sodium Deficiency Reduces Sodium Excretion but Impairs Renal Function and Increases Stone Formation in Hyperoxaluric Calcium Oxalate Rats. Int J Mol Sci 2024; 25:3942. [PMID: 38612752 PMCID: PMC11011831 DOI: 10.3390/ijms25073942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2024] [Revised: 03/19/2024] [Accepted: 03/25/2024] [Indexed: 04/14/2024] Open
Abstract
Excessive sodium intake is associated with nephrolithiasis, but the impact of sodium-deficient (SD) diets is unknown. Hence, we investigated the effects of short- and long-term SD diets on the expression of renal aquaporins and sodium transporters, and thus calcium oxalate (CaOx) crystal formation in hyperoxaluria rats. In a short-term sodium balance study, six male rats received drinking water and six received 0.75% ethylene glycol (EG) to induce hyperoxaluria. After a 30-day period of feeding on normal chow, both groups were treated with a normal-sodium diet for 5 days, followed by a sodium-free diet for the next 5 days. In a long-term SD study (42 days), four groups, induced with EG or not, were treated with normal-sodium water and sodium-free drinking water, alternately. Short-term sodium restriction in EG rats reversed the daily positive sodium balance, but progressively caused a negative cumulative water balance. In the long-term study, the abundant levels of of Na/H exchanger, thiazide-sensitive Na-Cl cotransporter, Na-K-ATPase, and aquaporins-1 from SD + EG rats were markedly reduced, corresponding to a decrease in Uosm, as compared to SD rats. Increased urine calcium, AP(CaOx)index, and renal CaOx deposition were also noted in SD + EG rats. Although the SD treatment reduced sodium excretion, it also increased urinary calcium and impaired renal function, ultimately causing the formation of more CaOx crystals.
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Affiliation(s)
| | | | | | - Ho-Shiang Huang
- Department of Urology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan 704302, Taiwan; (Y.-C.H.); (C.-J.L.); (Z.-H.L.)
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Dominguez Rieg JA, Rieg T. New functions and roles of the Na +-H +-exchanger NHE3. Pflugers Arch 2024; 476:505-516. [PMID: 38448727 DOI: 10.1007/s00424-024-02938-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 02/22/2024] [Accepted: 02/27/2024] [Indexed: 03/08/2024]
Abstract
The sodium/proton exchanger isoform 3 (NHE3) is expressed in the intestine and the kidney, where it contributes to hydrogen secretion and sodium (re)absorption. The roles of this transporter have been studied by the use of the respective knockout mice and by using pharmacological inhibitors. Whole-body NHE3 knockout mice suffer from a high mortality rate (with only ∼30% of mice surviving into adulthood), and based on the expression of NHE3 in both intestine and kidney, some conclusions that were originally derived were based on this rather complex phenotype. In the last decade, more refined models have been developed that added temporal and spatial control of NHE3 expression. For example, novel mouse models have been developed with a knockout of NHE3 in intestinal epithelial cells, tubule/collecting duct of the kidney, proximal tubule of the kidney, and thick ascending limb of the kidney. These refined models have significantly contributed to our understanding of the role of NHE3 in a tissue/cell type-specific manner. In addition, tenapanor was developed, which is a non-absorbable, intestine-specific NHE3 inhibitor. In rat and human studies, tenapanor lowered intestinal Pi uptake and was effective in lowering plasma Pi levels in patients on hemodialysis. Of note, diarrhea is seen as a side effect of tenapanor (with its indication for the treatment of constipation) and in intestine-specific NHE3 knockout mice; however, effects on plasma Pi were not supported by this mouse model which showed enhanced and not reduced intestinal Pi uptake. Further studies indicated that the gut microbiome in mice lacking intestinal NHE3 resembles an intestinal environment favoring the competitive advantage of inflammophilic over anti-inflammatory species, something similar seen in patients with inflammatory bowel disease. This review will highlight recent developments and summarize newly gained insight from these refined models.
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Affiliation(s)
- Jessica A Dominguez Rieg
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL, 33612, USA
- James A. Haley Veterans' Hospital, Tampa, FL, 33612, USA
- Hypertension and Kidney Research Center, University of South Florida, Tampa, FL, 33602, USA
| | - Timo Rieg
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, FL, 33612, USA.
- James A. Haley Veterans' Hospital, Tampa, FL, 33612, USA.
- Hypertension and Kidney Research Center, University of South Florida, Tampa, FL, 33602, USA.
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3
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Duan XP, Xiao Y, Su XT, Zheng JY, Gurley S, Emathinger J, Yang CL, McCormick J, Ellison DH, Lin DH, Wang WH. Role of Angiotensin II Type 1a Receptor (AT1aR) of Renal Tubules in Regulating Inwardly Rectifying Potassium Channels 4.2 (Kir4.2), Kir4.1, and Epithelial Na + Channel (ENaC). Hypertension 2024; 81:126-137. [PMID: 37909221 PMCID: PMC10842168 DOI: 10.1161/hypertensionaha.123.21389] [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: 04/19/2023] [Accepted: 10/12/2023] [Indexed: 11/02/2023]
Abstract
BACKGROUND Kir4.2 and Kir4.1 play a role in regulating membrane transport in the proximal tubule (PT) and in the distal-convoluted-tubule (DCT), respectively. METHODS We generated kidney-tubule-specific-AT1aR-knockout (Ks-AT1aR-KO) mice to examine whether renal AT1aR regulates Kir4.2 and Kir4.1. RESULTS Ks-AT1aR-KO mice had a lower systolic blood pressure than Agtr1aflox/flox (control) mice. Ks-AT1aR-KO mice had a lower expression of NHE3 (Na+/H+-exchanger 3) and Kir4.2, a major Kir-channel in PT, than Agtr1aflox/flox mice. Whole-cell recording also demonstrated that the membrane potential in PT of Ks-AT1aR-KO mice was lesser negative than Agtr1aflox/flox mice. The expression of Kir4.1 and Kir5.1, Kir4.1/Kir5.1-mediated K+ currents of DCT and DCT membrane potential in Ks-AT1aR-KO mice, were similar to Agtr1aflox/flox mice. However, angiotensin II perfusion for 7 days hyperpolarized the membrane potential in PT and DCT of the control mice but not in Ks-AT1aR-KO mice, while angiotensin II perfusion did not change the expression of Kir4.1, Kir4.2, and Kir5.1. Deletion of AT1aR did not significantly affect the expression of αENaC (epithelial Na+ channel) and βENaC but increased cleaved γENaC expression. Patch-clamp experiments demonstrated that deletion of AT1aR increased amiloride-sensitive Na+-currents in the cortical-collecting duct but not in late-DCT. However, tertiapin-Q sensitive renal outer medullary potassium channel currents were similar in both genotypes. CONCLUSIONS AT1aR determines the baseline membrane potential of PT by controlling Kir4.2 expression/activity but AT1aR is not required for determining the baseline membrane potential of the DCT and Kir4.1/Kir5.1 activity/expression. However, AT1aR is required for angiotensin II-induced hyperpolarization of basolateral membrane of PT and DCT. Deletion of AT1aR had no effect on baseline renal outer medullary potassium channel activity but increased ENaC activity in the CCD.
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Affiliation(s)
- Xin-Peng Duan
- Department of Physiology, Xuzhou Medical University, Xuzhou, China
- Department of Pharmacology, New York Medical College, Valhalla, NY
| | - Yu Xiao
- Department of Physiology, Qiqihar Medical College, Heilongjiang, China
- Department of Pharmacology, New York Medical College, Valhalla, NY
| | - Xiao-Tong Su
- Department of Medicine, Oregon Health & Science University, Portland, Oregon
| | - Jun-Ya Zheng
- Department of Pharmacology, New York Medical College, Valhalla, NY
| | - Susan Gurley
- Department of Medicine, Oregon Health & Science University, Portland, Oregon
| | | | - Chao-Ling Yang
- Department of Medicine, Oregon Health & Science University, Portland, Oregon
| | - James McCormick
- Department of Medicine, Oregon Health & Science University, Portland, Oregon
| | - David H. Ellison
- Department of Medicine, Oregon Health & Science University, Portland, Oregon
| | - Dao-Hong Lin
- Department of Pharmacology, New York Medical College, Valhalla, NY
| | - Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, NY
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4
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Goto S, Yoshida Y, Hosojima M, Kuwahara S, Kabasawa H, Aoki H, Iida T, Sawada R, Ugamura D, Yoshizawa Y, Takemoto K, Komochi K, Kobayashi R, Kaseda R, Yaoita E, Nagatoishi S, Narita I, Tsumoto K, Saito A. Megalin is involved in angiotensinogen-induced, angiotensin II-mediated ERK1/2 signaling to activate Na + -H + exchanger 3 in proximal tubules. J Hypertens 2023; 41:1831-1843. [PMID: 37682076 DOI: 10.1097/hjh.0000000000003555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/09/2023]
Abstract
BACKGROUND Kidney angiotensin (Ang) II is produced mainly from liver-derived, glomerular-filtered angiotensinogen (AGT). Podocyte injury has been reported to increase the kidney Ang II content and induce Na + retention depending on the function of megalin, a proximal tubular endocytosis receptor. However, how megalin regulates the renal content and action of Ang II remains elusive. METHODS We used a mass spectrometry-based, parallel reaction-monitoring assay to quantitate Ang II in plasma, urine, and kidney homogenate of kidney-specific conditional megalin knockout (MegKO) and control (Ctl) mice. We also evaluated the pathophysiological changes in both mouse genotypes under the basal condition and under the condition of increased glomerular filtration of AGT induced by administration of recombinant mouse AGT (rec-mAGT). RESULTS Under the basal condition, plasma and kidney Ang II levels were comparable in the two mouse groups. Ang II was detected abundantly in fresh spot urine in conditional MegKO mice. Megalin was also found to mediate the uptake of intravenously administered fluorescent Ang II by PTECs. Administration of rec-mAGT increased kidney Ang II, exerted renal extracellular signal-regulated kinase 1/2 (ERK1/2) signaling, activated proximal tubular Na + -H + exchanger 3 (NHE3), and decreased urinary Na + excretion in Ctl mice, whereas these changes were suppressed but urinary Ang II was increased in conditional MegKO mice. CONCLUSION Increased glomerular filtration of AGT is likely to augment Ang II production in the proximal tubular lumen. Thus, megalin-dependent Ang II uptake should be involved in the ERK1/2 signaling that activates proximal tubular NHE3 in vivo , thereby causing Na + retention.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | - Ryohei Kaseda
- Department of Clinical Nephrology and Rheumatology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata City, Niigata
| | | | | | - Ichiei Narita
- Department of Clinical Nephrology and Rheumatology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata City, Niigata
| | - Kouhei Tsumoto
- The Institute of Medical Science and Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
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Tang H, Xu C, Zhang P, Luo T, Huang Y, Yang X. A profile of SGLT-2 inhibitors in hyponatremia: The evidence to date. Eur J Pharm Sci 2023; 184:106415. [PMID: 36870579 DOI: 10.1016/j.ejps.2023.106415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 02/14/2023] [Accepted: 02/27/2023] [Indexed: 03/06/2023]
Abstract
Hyponatremia is the most common electrolyte disorder in clinical practice, which may lead to life-threatening complications. Several lines of evidence suggest that hyponatremia is associated not only with significant increases in length of stay, cost, and financial burden, but also with increased morbidity and mortality. Hyponatremia is also considered to be a negative prognostic factor in patients with heart failure and cancer. Although multiple therapeutic methods are available for treating hyponatremia, most have some limitations, such as poor compliance, rapid correction of serum Na+, other negative side effects and high cost. Given these limitations, identifying novel therapies for hyponatremia is essential. Recent clinical studies have shown that SGLT-2 inhibitors (SGLT 2i) significantly increased serum Na+ levels and were well tolerated by patients who underwent this treatment. Therefore, oral administration of SGLT 2i appears to be an effective treatment for hyponatremia. This article will briefly review the etiology of hyponatremia and integrated control of sodium within the kidney, current therapies for hyponatremia, potential mechanisms and efficacy of SGLT 2i for hyponatremia, and the benefits in cardiovascular, cancer, and kidney disease by regulating sodium and water balance.
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Affiliation(s)
- Hui Tang
- Department of Pharmacy, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China; School of Pharmacy, Southwest Medical University, Luzhou 646000, China
| | - Changjing Xu
- Department of Pharmacy, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China
| | - Piao Zhang
- Department of Pharmacy, Ya 'an People's Hospital, Ya 'an, Sichuan 646000, China
| | - Taimin Luo
- Department of pharmacy, Chengdu Seventh People's Hospital, Chengdu, Sichuan 610000, China
| | - Yilan Huang
- Department of Pharmacy, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China; School of Pharmacy, Southwest Medical University, Luzhou 646000, China.
| | - Xuping Yang
- Department of Pharmacy, The Affiliated Hospital of Southwest Medical University, Luzhou 646000, China; School of Pharmacy, Southwest Medical University, Luzhou 646000, China.
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6
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Shih SW, Yan JJ, Lu SW, Chuang YT, Lin HW, Chou MY, Hwang PP. Molecular Physiological Evidence for the Role of Na+-Cl− Co-Transporter in Branchial Na+ Uptake in Freshwater Teleosts. Int J Mol Sci 2023; 24:ijms24076597. [PMID: 37047570 PMCID: PMC10094795 DOI: 10.3390/ijms24076597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 03/23/2023] [Accepted: 03/30/2023] [Indexed: 04/05/2023] Open
Abstract
The gills are the major organ for Na+ uptake in teleosts. It was proposed that freshwater (FW) teleosts adopt Na+/H+ exchanger 3 (Nhe3) as the primary transporter for Na+ uptake and Na+-Cl− co-transporter (Ncc) as the backup transporter. However, convincing molecular physiological evidence to support the role of Ncc in branchial Na+ uptake is still lacking due to the limitations of functional assays in the gills. Thus, this study aimed to reveal the role of branchial Ncc in Na+ uptake with an in vivo detection platform (scanning ion-selective electrode technique, SIET) that has been recently established in fish gills. First, we identified that Ncc2-expressing cells in zebrafish gills are a specific subtype of ionocyte (NCC ionocytes) by using single-cell transcriptome analysis and immunofluorescence. After a long-term low-Na+ FW exposure, zebrafish increased branchial Ncc2 expression and the number of NCC ionocytes and enhanced gill Na+ uptake capacity. Pharmacological treatments further suggested that Na+ is indeed taken up by Ncc, in addition to Nhe, in the gills. These findings reveal the uptake roles of both branchial Ncc and Nhe under FW and shed light on osmoregulatory physiology in adult fish.
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Affiliation(s)
- Shang-Wu Shih
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115201, Taiwan
- Department of Life Science, National Taiwan University, Taipei 106319, Taiwan
| | - Jia-Jiun Yan
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115201, Taiwan
| | - Shao-Wei Lu
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115201, Taiwan
| | - Ya-Ting Chuang
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115201, Taiwan
| | - How-Wei Lin
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115201, Taiwan
- Department of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung 202301, Taiwan
| | - Ming-Yi Chou
- Department of Life Science, National Taiwan University, Taipei 106319, Taiwan
| | - Pung-Pung Hwang
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115201, Taiwan
- Department of Life Science, National Taiwan University, Taipei 106319, Taiwan
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7
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Dorel R, Wong AR, Crawford JJ. Trust Your Gut: Strategies and Tactics for Intestinally Restricted Drugs. ACS Med Chem Lett 2023; 14:233-243. [PMID: 36923921 PMCID: PMC10009798 DOI: 10.1021/acsmedchemlett.3c00001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 02/02/2023] [Indexed: 02/24/2023] Open
Abstract
Non-absorbable small-molecule drugs targeted to the gut represent an alternative approach to safe, non-systemic therapeutics. Such drugs remain confined to the gastrointestinal tract upon oral dosing by virtue of their limited passive permeability, increasing the local concentration at the site of action while minimizing exposure elsewhere in the body. Herein we review the latest advances in the field of gut-restricted therapeutics, highlighting the different strategies and tactics that medicinal chemists have employed in pursuit of drugs with minimal intestinal absorption.
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Affiliation(s)
- Ruth Dorel
- Genentech, Inc., South San Francisco, California 94080, United States
| | - Alice R. Wong
- Genentech, Inc., South San Francisco, California 94080, United States
| | - James J. Crawford
- Genentech, Inc., South San Francisco, California 94080, United States
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8
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Chen KC, Chang ML, Lin CS, Rajneesh CP, Liao CH, You WC, Maa HC, Wu YN. Insight into SLC9A3 deficiency-mediated micturition dysfunction caused by electrolyte imbalance. Biomed Pharmacother 2023; 158:114155. [PMID: 36916397 DOI: 10.1016/j.biopha.2022.114155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 12/14/2022] [Accepted: 12/21/2022] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Solute carrier family nine isoform 3 (SLC9A3) is an Na+/H+ exchanger that regulates Ca2+ homeostasis. SLC9A3 is largely involved in the transepithelial absorption of Na+/H+ and frequently functions in pair with a Cl-/HCO3- exchanger. OBJECTIVE To investigate the impact and pathophysiological mechanisms of long-term SLC9A3 deficiency on lower urinary tract symptoms (LUTS) in a mouse model MATERIALS AND METHODS: Slc9a3 knockout and wild-type mice (average >6 months) were used. The effects of SLC9A3 depletion on bladder and urethral functions and effectiveness of voiding were assessed using a cystometrogram (CMG). Histology, blood electrolytes, and gene expression were also analyzed. RESULTS The SLC9A3-deficient mice had smaller gross bladders than the wild-type mice. The CMG analysis revealed normal peak micturition pressure, higher threshold pressure, short intercontraction interval, less voided volume, and poor compliance in the SLC9A3-deficient mice, similar to clinical LUTS. Histological analysis revealed loose detrusor muscle and loss of transformability of the urothelium in the SLC9A3-deficient mice. Masson's trichrome analysis revealed severe collagen deposition in the detrusor muscle. Immunofluorescence staining also demonstrated a significant decrease in cytokeratins 5 and 20. Gene and protein expression analyses confirmed that SLC9A3 does not act directly on bladder tissue. Homeostasis was correlated with bladder dysfunction in the SLC9A3-deficient mice. DISCUSSION Fibrosis and collagen deposition in the bladder of the SLC9A3-deficient mice is due to bladder inflammation because of decreased blood flow and deregulated systemic homeostasis. Long-term SLC9A3 depletion causes progressive bladder dysfunction, similar to human LUTS. CONCLUSION Electrolyte imbalance causes SLC9A3 deficiency-mediated progressive micturition dysfunction.
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Affiliation(s)
- Kuo-Chiang Chen
- School of Medicine, College of Medicine, Fu Jen Catholic University, New Taipei City 242062, Taiwan; Department of Urology, Cathay General Hospital, Taipei City 106438, Taiwan
| | - Meng-Lin Chang
- School of Medicine, College of Medicine, Fu Jen Catholic University, New Taipei City 242062, Taiwan; Department of Urology, Fu Jen Catholic University Hospital, Fu Jen Catholic University, New Taipei City 243089, Taiwan
| | - Chun-Sian Lin
- Graduate Institute of Biomedical and Pharmaceutical Science, College of Medicine, Fu Jen Catholic University, New Taipei City 242062, Taiwan
| | | | - Chun-Hou Liao
- School of Medicine, College of Medicine, Fu Jen Catholic University, New Taipei City 242062, Taiwan; Division of Urology, Department of Surgery, Cardinal Tien Hospital, New Taipei City 231403, Taiwan
| | - Wen-Chen You
- School of Medicine, College of Medicine, Fu Jen Catholic University, New Taipei City 242062, Taiwan
| | - Hung-Chune Maa
- School of Medicine, College of Medicine, Fu Jen Catholic University, New Taipei City 242062, Taiwan; Department of Pathology, Cardinal Tien Hospital, New Taipei City 231403, Taiwan.
| | - Yi-No Wu
- School of Medicine, College of Medicine, Fu Jen Catholic University, New Taipei City 242062, Taiwan.
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The Post-Translational Modification Networking in WNK-Centric Hypertension Regulation and Electrolyte Homeostasis. Biomedicines 2022; 10:biomedicines10092169. [PMID: 36140271 PMCID: PMC9496095 DOI: 10.3390/biomedicines10092169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 08/26/2022] [Accepted: 08/27/2022] [Indexed: 11/17/2022] Open
Abstract
The with-no-lysine (WNK) kinase family, comprising four serine-threonine protein kinases (WNK1-4), were first linked to hypertension due to their mutations in association with pseudohypoaldosteronism type II (PHAII). WNK kinases regulate crucial blood pressure regulators, SPAK/OSR1, to mediate the post-translational modifications (PTMs) of their downstream ion channel substrates, such as sodium chloride co-transporter (NCC), epithelial sodium chloride (ENaC), renal outer medullary potassium channel (ROMK), and Na/K/2Cl co-transporters (NKCCs). In this review, we summarize the molecular pathways dysregulating the WNKs and their downstream target renal ion transporters. We summarize each of the genetic variants of WNK kinases and the small molecule inhibitors that have been discovered to regulate blood pressure via WNK-triggered PTM cascades.
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10
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O'Connor AT, Haspula D, Alanazi AZ, Clark MA. Roles of Angiotensin III in the brain and periphery. Peptides 2022; 153:170802. [PMID: 35489649 DOI: 10.1016/j.peptides.2022.170802] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 04/21/2022] [Accepted: 04/25/2022] [Indexed: 10/18/2022]
Abstract
Angiotensin (Ang) III, a biologically active peptide of the renin angiotensin system (RAS) is predominantly known for its central effects on blood pressure. Our understanding of the RAS has evolved from the simplified, classical RAS, a hormonal system regulating blood pressure to a complex system affecting numerous biological processes. Ang II, the main RAS peptide has been widely studied, and its deleterious effects when overexpressed is well-documented. However, other components of the RAS such as Ang III are not well studied. This review examines the molecular and biological actions of Ang III and provides insight into Ang III's potential role in metabolic diseases.
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Affiliation(s)
- Ann Tenneil O'Connor
- Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Fort Lauderdale, FL, USA
| | - Dhanush Haspula
- Molecular Signaling Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD NIH-20892, USA
| | - Ahmed Z Alanazi
- Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia
| | - Michelle A Clark
- Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Fort Lauderdale, FL, USA.
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11
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Xue J, Dominguez Rieg JA, Thomas L, White JR, Rieg T. Intestine-Specific NHE3 Deletion in Adulthood Causes Microbial Dysbiosis. Front Cell Infect Microbiol 2022; 12:896309. [PMID: 35719363 PMCID: PMC9204535 DOI: 10.3389/fcimb.2022.896309] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 04/21/2022] [Indexed: 11/13/2022] Open
Abstract
In the intestine, the Na+/H+ exchanger 3 (NHE3) plays a critical role for Na+ and fluid absorption. NHE3 deficiency predisposes patients to inflammatory bowel disease (IBD). In mice, selective deletion of intestinal NHE3 causes various local and systemic pathologies due to dramatic changes in the intestinal environment, which can influence microbiota colonization. By using metagenome shotgun sequencing, we determined the effect of inducible intestinal epithelial cell-specific deletion of NHE3 (NHE3IEC-KO) in adulthood on the gut microbiome in mice. Compared with control mice, NHE3IEC-KO mice show a significantly different gut microbiome signature, with an unexpected greater diversity. At the phylum level, NHE3IEC-KO mice showed a significant expansion in Proteobacteria and a tendency for lower Firmicutes/Bacteroidetes (F/B) ratio, an indicator of dysbiosis. At the family level, NHE3IEC-KO mice showed significant expansions in Bacteroidaceae, Rikenellaceae, Tannerellaceae, Flavobacteriaceae and Erysipelotrichaceae, but had contractions in Lachnospiraceae, Prevotellaceae and Eubacteriaceae. At the species level, after removing those with lowest occurrence and abundance, we identified 23 species that were significantly expanded (several of which are established pro-inflammatory pathobionts); whereas another 23 species were found to be contracted (some of which are potential anti-inflammatory probiotics) in NHE3IEC-KO mice. These results reveal that intestinal NHE3 deletion creates an intestinal environment favoring the competitive advantage of inflammophilic over anti-inflammatory species, which is commonly featured in conventional NHE3 knockout mice and patients with IBD. In conclusion, our study emphasizes the importance of intestinal NHE3 for gut microbiota homeostasis, and provides a deeper understanding regarding interactions between NHE3, dysbiosis, and IBD.
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Affiliation(s)
- Jianxiang Xue
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL, United States
| | - Jessica A Dominguez Rieg
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL, United States.,James A. Haley Veterans' Hospital, Tampa, FL, United States
| | - Linto Thomas
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL, United States
| | - James R White
- Resphera Biosciences LLC, Baltimore, MD, United States
| | - Timo Rieg
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL, United States.,James A. Haley Veterans' Hospital, Tampa, FL, United States.,Center for Hypertension and Kidney Research, University of South Florida, Tampa, FL, United States
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12
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Inverse Salt Sensitivity of Blood Pressure: Mechanisms and Potential Relevance for Prevention of Cardiovascular Disease. Curr Hypertens Rep 2022; 24:361-374. [PMID: 35708819 DOI: 10.1007/s11906-022-01201-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/07/2022] [Indexed: 11/03/2022]
Abstract
PURPOSE OF REVIEW To review the etiology of inverse salt sensitivity of blood pressure (BP). RECENT FINDINGS Both high and low sodium (Na+) intake can be associated with increased BP and cardiovascular morbidity and mortality. However, little is known regarding the mechanisms involved in the increase in BP in response to low Na+ intake, a condition termed inverse salt sensitivity of BP, which affects approximately 15% of the adult population. The renal proximal tubule is important in regulating up to 70% of renal Na+ transport. The renin-angiotensin and renal dopaminergic systems play both synergistic and opposing roles in the regulation of Na+ transport in this nephron segment. Clinical studies have demonstrated that individuals express a "personal salt index" (PSI) that marks whether they are salt-resistant, salt-sensitive, or inverse salt-sensitive. Inverse salt sensitivity results in part from genetic polymorphisms in various Na+ regulatory genes leading to a decrease in natriuretic activity and an increase in renal tubular Na+ reabsorption leading to an increase in BP. This article reviews the potential mechanisms of a new pathophysiologic entity, inverse salt sensitivity of BP, which affects approximately 15% of the general adult population.
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13
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Xue J, Thomas L, Dominguez Rieg JA, Fenton RA, Rieg T. NHE3 in the thick ascending limb is required for sustained but not acute furosemide-induced urinary acidification. Am J Physiol Renal Physiol 2022; 323:F141-F155. [PMID: 35635321 PMCID: PMC9306792 DOI: 10.1152/ajprenal.00013.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The Na+/H+ exchanger isoform 3 (NHE3) facilitates Na+ reabsorption and H+ secretion by the kidneys. Despite stronger NHE3 abundance in the thick ascending limb (TAL) compared to the S1 and S2 segments of the proximal tubule, the role of NHE3 in the TAL is poorly understood. To investigate the role of NHE3 in the TAL, we generated and phenotyped TAL-specific NHE3 knockout mice (NHE3TAL-KO). Compared to control mice, NHE3TAL-KO mice did not show significant differences in body weight, blood pH or plasma Na+, K+ or Cl- levels. Fluid intake trended to be higher and urine osmolality was significantly lower in NHE3TAL-KO mice. Despite a similar GFR, NHE3TAL-KO mice had a greater urinary K+/creatinine ratio. One proposed role of NHE3 relates to furosemide-induced urinary acidification. Acute bolus treatment with furosemide under anesthesia did not result in differences in the dose dependence of urinary flow rate, Cl- excretion or maximal urinary acidification between genotypes; however, in contrast to control mice, urinary pH returned immediately towards baseline levels in NHE3TAL-KO mice. Chronic furosemide treatment reduced urine osmolality similarly in both genotypes but metabolic alkalosis, hypokalemia and calciuresis were absent in NHE3TAL-KO mice. Compared to vehicle, chronic furosemide treatment in control mice resulted in greater NKCC2 and lower Npt2a abundances, effects that were absent in NHE3TAL-KO mice. In summary, NHE3 in the TAL plays a role for the sustained acidification effect of furosemide. Consistent with this, long-term treatment with furosemide did not result in metabolic alkalosis in NHE3TAL-KO mice.
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Affiliation(s)
- Jianxiang Xue
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States
| | - Linto Thomas
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States
| | - Jessica A Dominguez Rieg
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States.,James A. Haley Veterans' Hospital, Tampa, Florida, United States
| | - Robert A Fenton
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Timo Rieg
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States.,James A. Haley Veterans' Hospital, Tampa, Florida, United States.,Hypertension and Kidney Research Center, University of South Florida, Tampa, FL, United States
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14
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Nwia SM, Li XC, Leite APDO, Hassan R, Zhuo JL. The Na +/H + Exchanger 3 in the Intestines and the Proximal Tubule of the Kidney: Localization, Physiological Function, and Key Roles in Angiotensin II-Induced Hypertension. Front Physiol 2022; 13:861659. [PMID: 35514347 PMCID: PMC9062697 DOI: 10.3389/fphys.2022.861659] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 02/25/2022] [Indexed: 01/29/2023] Open
Abstract
The sodium (Na+)/hydrogen (H+) exchanger 3 (NHE3) is one of the most important Na+/H+ antiporters in the small intestines of the gastrointestinal tract and the proximal tubules of the kidney. The roles of NHE3 in the regulation of intracellular pH and acid-base balance have been well established in cellular physiology using in vitro techniques. Localized primarily on the apical membranes in small intestines and proximal tubules, the key action of NHE3 is to facilitate the entry of luminal Na+ and the extrusion of intracellular H+ from intestinal and proximal tubule tubular epithelial cells. NHE3 is, directly and indirectly, responsible for absorbing the majority of ingested Na+ from small and large intestines and reabsorbing >50% of filtered Na+ in the proximal tubules of the kidney. However, the roles of NHE3 in the regulation of proximal tubular Na+ transport in the integrative physiological settings and its contributions to the basal blood pressure regulation and angiotensin II (Ang II)-induced hypertension have not been well studied previously due to the lack of suitable animal models. Recently, novel genetically modified mouse models with whole-body, kidney-specific, or proximal tubule-specific deletion of NHE3 have been generated by us and others to determine the critical roles and underlying mechanisms of NHE3 in maintaining basal body salt and fluid balance, blood pressure homeostasis, and the development of Ang II-induced hypertension at the whole-body, kidney, or proximal tubule levels. The objective of this invited article is to review, update, and discuss recent findings on the critical roles of intestinal and proximal tubule NHE3 in maintaining basal blood pressure homeostasis and their potential therapeutic implications in the development of angiotensin II (Ang II)-dependent hypertension.
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Affiliation(s)
- Sarah M. Nwia
- Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA, United States,Department of Physiology, Tulane University School of Medicine, New Orleans, LA, United States
| | - Xiao Chun Li
- Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA, United States,Department of Physiology, Tulane University School of Medicine, New Orleans, LA, United States
| | - Ana Paula de Oliveira Leite
- Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA, United States,Department of Physiology, Tulane University School of Medicine, New Orleans, LA, United States
| | - Rumana Hassan
- Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA, United States,Department of Physiology, Tulane University School of Medicine, New Orleans, LA, United States
| | - Jia Long Zhuo
- Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA, United States,Department of Physiology, Tulane University School of Medicine, New Orleans, LA, United States,*Correspondence: Jia Long Zhuo,
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15
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Jacobs JW, Leadbetter MR, Bell N, Koo-McCoy S, Carreras CW, He L, Kohler J, Kozuka K, Labonté ED, Navre M, Spencer AG, Charmot D. Discovery of Tenapanor: A First-in-Class Minimally Systemic Inhibitor of Intestinal Na +/H + Exchanger Isoform 3. ACS Med Chem Lett 2022; 13:1043-1051. [PMID: 35859876 PMCID: PMC9290029 DOI: 10.1021/acsmedchemlett.2c00037] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
![]()
We present herein
the design, synthesis, and optimization of gut-restricted
inhibitors of Na+/H+ exchanger isoform 3 (NHE3).
NHE3 is predominantly expressed in the kidney and gastrointestinal
tract where it acts as the major absorptive sodium transporter. We
desired minimally systemic agents that would block sodium absorption
in the gastrointestinal tract but avoid exposure in the kidney. Starting
with a relatively low-potency highly bioavailable hit compound (1), potent and minimally absorbed NHE3 inhibitors were designed,
culminating with the discovery of tenapanor (28). Tenapanor
has been approved by the U.S. Food and Drug Administration (FDA) for
the treatment of irritable bowel syndrome with constipation in adults.
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Affiliation(s)
- Jeffrey W. Jacobs
- Ardelyx, Inc., 400 Fifth Avenue, Suite 210, Waltham, Massachusetts 02451, United States
| | - Michael R. Leadbetter
- Ardelyx, Inc., 400 Fifth Avenue, Suite 210, Waltham, Massachusetts 02451, United States
| | - Noah Bell
- Ardelyx, Inc., 400 Fifth Avenue, Suite 210, Waltham, Massachusetts 02451, United States
| | - Samantha Koo-McCoy
- Ardelyx, Inc., 400 Fifth Avenue, Suite 210, Waltham, Massachusetts 02451, United States
| | | | - Limin He
- Ardelyx, Inc., 400 Fifth Avenue, Suite 210, Waltham, Massachusetts 02451, United States
| | - Jill Kohler
- Ardelyx, Inc., 400 Fifth Avenue, Suite 210, Waltham, Massachusetts 02451, United States
| | - Kenji Kozuka
- Ardelyx, Inc., 400 Fifth Avenue, Suite 210, Waltham, Massachusetts 02451, United States
| | - Eric D. Labonté
- Ardelyx, Inc., 400 Fifth Avenue, Suite 210, Waltham, Massachusetts 02451, United States
| | - Marc Navre
- Ardelyx, Inc., 400 Fifth Avenue, Suite 210, Waltham, Massachusetts 02451, United States
| | - Andrew G. Spencer
- Ardelyx, Inc., 400 Fifth Avenue, Suite 210, Waltham, Massachusetts 02451, United States
| | - Dominique Charmot
- Ardelyx, Inc., 400 Fifth Avenue, Suite 210, Waltham, Massachusetts 02451, United States
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16
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Xue J, Thomas L, Murali SK, Levi M, Fenton RA, Dominguez Rieg JA, Rieg T. Enhanced phosphate absorption in intestinal epithelial cell-specific NHE3 knockout mice. Acta Physiol (Oxf) 2022; 234:e13756. [PMID: 34978760 PMCID: PMC9286053 DOI: 10.1111/apha.13756] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 11/16/2021] [Accepted: 01/01/2022] [Indexed: 12/11/2022]
Abstract
Aims The kidneys play a major role in maintaining Pi homeostasis. Patients in later stages of CKD develop hyperphosphatemia. One novel treatment option is tenapanor, an intestinal‐specific NHE3 inhibitor. To gain mechanistic insight into the role of intestinal NHE3 in Pi homeostasis, we studied tamoxifen‐inducible intestinal epithelial cell‐specific NHE3 knockout (NHE3IEC‐KO) mice. Methods Mice underwent dietary Pi challenges, and hormones as well as urinary/plasma Pi were determined. Intestinal 33P uptake studies were conducted in vivo to compare the effects of tenapanor and NHE3IEC‐KO. Ex vivo Pi transport was measured in everted gut sacs and brush border membrane vesicles. Intestinal and renal protein expression of Pi transporters were determined. Results On the control diet, NHE3IEC‐KO mice had similar Pi homeostasis, but a ~25% reduction in FGF23 compared with control mice. Everted gut sacs and brush border membrane vesicles showed enhanced Pi uptake associated with increased Npt2b expression in NHE3IEC‐KO mice. Acute oral Pi loading resulted in higher plasma Pi in NHE3IEC‐KO mice. Tenapanor inhibited intestinal 33P uptake acutely but then led to hyper‐absorption at later time points compared to vehicle. In response to high dietary Pi, plasma Pi and FGF23 increased to higher levels in NHE3IEC‐KO mice which was associated with greater Npt2b expression. Reduced renal Npt2c and a trend for reduced Npt2a expression were unable to correct for higher plasma Pi. Conclusion Intestinal NHE3 has a significant contribution to Pi homeostasis. In contrast to effects described for tenapanor on Pi homeostasis, NHE3IEC‐KO mice show enhanced, rather than reduced, intestinal Pi uptake.
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Affiliation(s)
- Jianxiang Xue
- Department of Molecular Pharmacology and Physiology Morsani College of Medicine University of South Florida Tampa Florida USA
| | - Linto Thomas
- Department of Molecular Pharmacology and Physiology Morsani College of Medicine University of South Florida Tampa Florida USA
| | | | - Moshe Levi
- Department of Biochemistry and Molecular & Cellular Biology Georgetown University Washington District of Columbia USA
| | | | - Jessica A. Dominguez Rieg
- Department of Molecular Pharmacology and Physiology Morsani College of Medicine University of South Florida Tampa Florida USA
- James A. Haley Veterans' Hospital Tampa Florida USA
| | - Timo Rieg
- Department of Molecular Pharmacology and Physiology Morsani College of Medicine University of South Florida Tampa Florida USA
- James A. Haley Veterans' Hospital Tampa Florida USA
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17
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Vargas-Poussou R. Pathophysiological aspects of the thick ascending limb and novel genetic defects: HELIX syndrome and transient antenatal Bartter syndrome. Pediatr Nephrol 2022; 37:239-252. [PMID: 33733301 DOI: 10.1007/s00467-021-05019-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 01/29/2021] [Accepted: 02/17/2021] [Indexed: 10/21/2022]
Abstract
The thick ascending limb plays a central role in human kidney physiology, participating in sodium reabsorption, urine concentrating mechanisms, calcium and magnesium homeostasis, bicarbonate and ammonium homeostasis, and uromodulin synthesis. This review aims to illustrate the importance of these roles from a pathophysiological point of view by describing the interactions of the key proteins of this segment and by discussing how recently identified and long-known hereditary diseases affect this segment. The descriptions of two recently described salt-losing tubulopathies, transient antenatal Bartter syndrome and HELIX syndrome, which are caused by mutations in MAGED2 and CLDN10 genes, respectively, highlight the role of new players in the modulation of sodium reabsorption the thick ascending limb.
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Affiliation(s)
- Rosa Vargas-Poussou
- Department of Molecular Genetics, Assistance Publique Hôpitaux de Paris, Hôpital Européen Georges-Pompidou, 20-40 rue Leblanc, 75015, Paris, France. .,Centre de Référence des Maladies Rénales Héréditaires de l'Enfant et de l'Adulte (MARHEA), Paris, France. .,Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Paris, France.
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18
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Li XC, Wang CH, Leite APO, Zhuo JL. Intratubular, Intracellular, and Mitochondrial Angiotensin II/AT 1 (AT1a) Receptor/NHE3 Signaling Plays a Critical Role in Angiotensin II-Induced Hypertension and Kidney Injury. Front Physiol 2021; 12:702797. [PMID: 34408663 PMCID: PMC8364949 DOI: 10.3389/fphys.2021.702797] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 05/24/2021] [Indexed: 12/14/2022] Open
Abstract
Hypertension is well recognized to be the most important risk factor for cardiovascular diseases, stroke, and end-stage kidney failure. A quarter of the world’s adult populations and 46% of the US adults develop hypertension and currently require antihypertensive treatments. Only 50% of hypertensive patients are responsive to current antihypertensive drugs, whereas remaining patients may continue to develop cardiovascular, stroke, and kidney diseases. The mechanisms underlying the poorly controlled hypertension remain incompletely understood. Recently, we have focused our efforts to uncover additional renal mechanisms, pathways, and therapeutic targets of poorly controlled hypertension and target organ injury using novel animal models or innovative experimental approaches. Specifically, we studied and elucidated the important roles of intratubular, intracellular, and mitochondrial angiotensin II (Ang II) system in the development of Ang II-dependent hypertension. The objectives of this invited article are to review and discuss our recent findings that (a) circulating and intratubular Ang II is taken up by the proximal tubules via the (AT1) AT1a receptor-dependent mechanism, (b) intracellular administration of Ang II in proximal tubule cells or adenovirus-mediated overexpression of an intracellular Ang II fusion protein selectively in the mitochonria of the proximal tubules induces blood pressure responses, and (c) genetic deletion of AT1 (AT1a) receptors or the Na+/H+ exchanger 3 selectively in the proximal tubules decreases basal blood pressure and attenuates Ang II-induced hypertension. These studies provide a new perspective into the important roles of the intratubular, intracellular, and mitochondrial angiotensin II/AT1 (AT1a) receptor signaling in Ang II-dependent hypertensive kidney diseases.
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Affiliation(s)
- Xiao Chun Li
- Tulane Hypertension and Renal Center of Excellence, Department of Physiology, Tulane University School of Medicine,New Orleans, LA, United States
| | - Chih-Hong Wang
- Tulane Hypertension and Renal Center of Excellence, Department of Physiology, Tulane University School of Medicine,New Orleans, LA, United States
| | - Ana Paula Oliveira Leite
- Tulane Hypertension and Renal Center of Excellence, Department of Physiology, Tulane University School of Medicine,New Orleans, LA, United States
| | - Jia Long Zhuo
- Tulane Hypertension and Renal Center of Excellence, Department of Physiology, Tulane University School of Medicine,New Orleans, LA, United States
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19
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New Insights into the Critical Importance of Intratubular Na +/H + Exchanger 3 and Its Potential Therapeutic Implications in Hypertension. Curr Hypertens Rep 2021; 23:34. [PMID: 34110521 DOI: 10.1007/s11906-021-01152-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/17/2021] [Indexed: 01/08/2023]
Abstract
PURPOSE OF REVIEW The sodium (Na+) and hydrogen (H+) exchanger 3 (NHE3), known as solute carrier family 9 member 3 (SLC9A3), mediates active transcellular Na+ and bicarbonate reabsorption in the small intestine of the gut and proximal tubules of the kidney. The purpose of this article is to review and discuss recent findings on the critical roles of intestinal and proximal tubule NHE3 in maintaining basal blood pressure (BP) homeostasis and their potential therapeutic implications in the development of angiotensin II (Ang II)-dependent hypertension. RECENT FINDINGS Recently, our and other laboratories have generated or used novel genetically modified mouse models with whole-body, kidney-specific, or proximal tubule-specific deletion of NHE3 to determine the critical roles and underlying mechanisms of NHE3 in maintaining basal BP homeostasis and the development of Ang II-induced hypertension at the whole-body, kidney, or proximal tubule levels. The new findings demonstrate that NHE3 contributes to about 10 to 15 mmHg to basal blood pressure levels, and that deletion of NHE3 at the whole-kidney or proximal tubule level, or pharmacological inhibition of NHE3 at the kidney level with an orally absorbable NHE3 inhibitor AVE-0657, attenuates ~ 50% of Ang II-induced hypertension in mice. The results support the proof-of-concept hypothesis that NHE3 plays critical roles in physiologically maintaining normal BP and in the development of Ang II-dependent hypertension. Our results also strongly suggest that NHE3 in the proximal tubules of the kidney may be therapeutically targeted to treat poorly controlled hypertension in humans.
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20
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Sung CC, Chen MH, Lin YC, Lin YC, Lin YJ, Yang SS, Lin SH. Urinary Extracellular Vesicles for Renal Tubular Transporters Expression in Patients With Gitelman Syndrome. Front Med (Lausanne) 2021; 8:679171. [PMID: 34179047 PMCID: PMC8219937 DOI: 10.3389/fmed.2021.679171] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 05/11/2021] [Indexed: 11/27/2022] Open
Abstract
Background: The utility of urinary extracellular vesicles (uEVs) to faithfully represent the changes of renal tubular protein expression remains unclear. We aimed to evaluate renal tubular sodium (Na+) or potassium (K+) associated transporters expression from uEVs and kidney tissues in patients with Gitelman syndrome (GS) caused by inactivating mutations in SLC12A3. Methods: uEVs were isolated by ultracentrifugation from 10 genetically-confirmed GS patients. Membrane transporters including Na+-hydrogen exchanger 3 (NHE3), Na+/K+/2Cl− cotransporter (NKCC2), NaCl cotransporter (NCC), phosphorylated NCC (p-NCC), epithelial Na+ channel β (ENaCβ), pendrin, renal outer medullary K1 channel (ROMK), and large-conductance, voltage-activated and Ca2+-sensitive K+ channel (Maxi-K) were examined by immunoblotting of uEVs and immunofluorescence of biopsied kidney tissues. Healthy and disease (bulimic patients) controls were also enrolled. Results: Characterization of uEVs was confirmed by nanoparticle tracking analysis, transmission electron microscopy, and immunoblotting. Compared with healthy controls, uEVs from GS patients showed NCC and p-NCC abundance were markedly attenuated but NHE3, ENaCβ, and pendrin abundance significantly increased. ROMK and Maxi-K abundance were also significantly accentuated. Immunofluorescence of the representative kidney tissues from GS patients also demonstrated the similar findings to uEVs. uEVs from bulimic patients showed an increased abundance of NCC and p-NCC as well as NHE3, NKCC2, ENaCβ, pendrin, ROMK and Maxi-K, akin to that in immunofluorescence of their kidney tissues. Conclusion: uEVs could be a non-invasive tool to diagnose and evaluate renal tubular transporter adaptation in patients with GS and may be applied to other renal tubular diseases.
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Affiliation(s)
- Chih-Chien Sung
- Division of Nephrology, Department of Medicine, National Defense Medical Center, Tri-Service General Hospital, Taipei, Taiwan
| | - Min-Hsiu Chen
- Division of Nephrology, Department of Medicine, National Defense Medical Center, Tri-Service General Hospital, Taipei, Taiwan
| | - Yi-Chang Lin
- Division of Cardiovascular Surgery, Department of Surgery, National Defense Medical Center, Tri-Service General Hospital, Taipei, Taiwan
| | - Yu-Chun Lin
- Deparment of Pathology, National Defense Medical Center, Tri-Service General Hospital, Taipei, Taiwan
| | - Yi-Jia Lin
- Deparment of Pathology, National Defense Medical Center, Tri-Service General Hospital, Taipei, Taiwan
| | - Sung-Sen Yang
- Division of Nephrology, Department of Medicine, National Defense Medical Center, Tri-Service General Hospital, Taipei, Taiwan
| | - Shih-Hua Lin
- Division of Nephrology, Department of Medicine, National Defense Medical Center, Tri-Service General Hospital, Taipei, Taiwan
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21
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Kinaneh S, Knany Y, Khoury EE, Ismael-Badarneh R, Hamoud S, Berger G, Abassi Z, Azzam ZS. Identification, localization and expression of NHE isoforms in the alveolar epithelial cells. PLoS One 2021; 16:e0239240. [PMID: 33882062 PMCID: PMC8059851 DOI: 10.1371/journal.pone.0239240] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Accepted: 04/02/2021] [Indexed: 02/06/2023] Open
Abstract
Na+/H+ exchangers (NHEs), encoded by Solute Carrier 9A (SLC9A) genes in human, are ubiquitous integral membrane ion transporters that mediate the electroneutral exchange of H+ with Na+ or K+. NHEs, found in the kidney and intestine, play a major role in the process of fluid reabsorption together via Na+,K+-ATPase pump and Na+ channels. Nevertheless, the expression pattern of NHE in the lung and its role in alveolar fluid homeostasis has not been addressed. Therefore, we aimed to examine the expression of NHE specific isoforms in alveolar epithelial cells (AECs), and assess their role in congestive heart failure (CHF). Three NHE isoforms were identified in AEC and A549 cell line, at the level of protein and mRNA; NHE1, NHE2 and mainly NHE8, the latter was shown to be localized in the apical membrane of AEC. Treating A549 cells with angiotensin (Ang) II for 3, 5 and 24 hours displayed a significant reduction in NHE8 protein abundance. Moreover, the abundance of NHE8 protein was downregulated in A549 cells that were treated overnight with Ang II. NHE8 abundance in whole lung lysate was increased in rats with 1-week CHF compared to sham operated rats. However, lower abundance of NHE8 was observed in 4-week CHF group. In conclusion, we herein show for the first time, the expression of a novel NHE isoform in AEC, namely NHE8. Notably, Ang II decreased NHE8 protein levels. Moreover, NHE8 was distinctly affected in CHF rats, probably depending on the severity of the heart failure.
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Affiliation(s)
- Safa Kinaneh
- Ruth & Bruce Rappaport Faculty of Medicine, Department of Physiology, Technion, Israel Institute of Technology, Haifa, Israel
| | - Yara Knany
- Ruth & Bruce Rappaport Faculty of Medicine, Department of Physiology, Technion, Israel Institute of Technology, Haifa, Israel
| | - Emad E. Khoury
- Ruth & Bruce Rappaport Faculty of Medicine, Department of Physiology, Technion, Israel Institute of Technology, Haifa, Israel
| | | | - Shadi Hamoud
- Ruth & Bruce Rappaport Faculty of Medicine, Department of Physiology, Technion, Israel Institute of Technology, Haifa, Israel
- Internal Medicine “E”, Rambam: Human Health Care Campus, Haifa, Israel
| | - Gidon Berger
- Ruth & Bruce Rappaport Faculty of Medicine, Department of Physiology, Technion, Israel Institute of Technology, Haifa, Israel
- Internal Medicine “B”, Rambam: Human Health Care Campus, Haifa, Israel
| | - Zaid Abassi
- Ruth & Bruce Rappaport Faculty of Medicine, Department of Physiology, Technion, Israel Institute of Technology, Haifa, Israel
| | - Zaher S. Azzam
- Ruth & Bruce Rappaport Faculty of Medicine, Department of Physiology, Technion, Israel Institute of Technology, Haifa, Israel
- Internal Medicine “B”, Rambam: Human Health Care Campus, Haifa, Israel
- * E-mail:
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22
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Nikolic M, Zivkovic V, Jovic JJ, Sretenovic J, Davidovic G, Simovic S, Djokovic D, Muric N, Bolevich S, Jakovljevic V. SGLT2 inhibitors: a focus on cardiac benefits and potential mechanisms. Heart Fail Rev 2021; 27:935-949. [PMID: 33534040 DOI: 10.1007/s10741-021-10079-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 01/21/2021] [Indexed: 12/16/2022]
Abstract
This paper highlights the cardioprotective potential of sodium-glucose cotransporter 2 inhibitors (SLGT2i), as well as several most discussed mechanisms responsible for their cardioprotection. Cardiovascular diseases are considered a primary cause of death in nearly 80% of type 2 diabetes mellitus (T2DM) patients, with a 2-4-fold greater incidence of heart failure (HF) among diabetics. As novel hypoglycemics, SGLT2i showed exceptional cardiovascular benefits, reflected through robust reductions of cardiovascular mortality and hospitalization for HF in T2DM patients. Recently, those effects have been reported even in patients with HF and reduced ejection fraction irrespectively of diabetic status, suggesting that cardioprotective effects of SGLT2i are driven independently of their hypoglycemic actions. SGLT2i exerted hemodynamic and metabolic effects, partially driven by natriuresis and osmotic diuresis. However, those systemic effects are modest, and therefore cannot be completely related to the cardiac benefits of these agents in T2DM patients. Hence, increased circulating ketone levels during SGLT2i administration have brought out another hypothesis of a cardiac metabolic switch. Moreover, SGLT2i influence ion homeostasis and exert anti-inflammatory and antifibrotic effects. Their enviable influence on oxidative stress markers, as well as anti- and pro-apoptotic factors, have also been reported. However, since the main mechanistical contributor of their cardioprotection has not been elucidated yet, a joint action of systemic and molecular mechanisms has been suggested. In the light of ongoing trials evaluating the effects of SGLT2i in patients with HF and preserved ejection fraction, a new chapter of beneficial SGLT2i mechanisms is expected, which might resolve their main underlying action.
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Affiliation(s)
- Maja Nikolic
- Department of Physiology, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia
| | - Vladimir Zivkovic
- Department of Physiology, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia
| | - Jovana Joksimovic Jovic
- Department of Physiology, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia
| | - Jasmina Sretenovic
- Department of Physiology, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia
| | - Goran Davidovic
- Department of Internal Medicine, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia
- Clinic of Cardiology, Clinical Center Kragujevac, Kragujevac, Serbia
| | - Stefan Simovic
- Department of Internal Medicine, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia
- Clinic of Cardiology, Clinical Center Kragujevac, Kragujevac, Serbia
| | - Danijela Djokovic
- Department of Psychiatry, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia
- Clinic of Psychiatry, Clinical Center Kragujevac, Kragujevac, Serbia
| | - Nemanja Muric
- Department of Psychiatry, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia
- Clinic of Psychiatry, Clinical Center Kragujevac, Kragujevac, Serbia
| | - Sergey Bolevich
- Department of Human Pathology, 1st Moscow State Medical University IM Sechenov, Moscow, Russia
| | - Vladimir Jakovljevic
- Department of Physiology, Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia.
- Department of Human Pathology, 1st Moscow State Medical University IM Sechenov, Moscow, Russia.
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23
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Xue J, Thomas L, Dominguez Rieg JA, Fenton RA, Rieg T. Genetic deletion of connexin 37 causes polyuria and polydipsia. PLoS One 2020; 15:e0244251. [PMID: 33332450 PMCID: PMC7746157 DOI: 10.1371/journal.pone.0244251] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 12/07/2020] [Indexed: 11/19/2022] Open
Abstract
The connexin 37 (Cx37) channel is clustered at gap junctions between cells in the renal vasculature or the renal tubule where it is abundant in basolateral cell interdigitations and infoldings of epithelial cells in the proximal tubule, thick ascending limb, distal convoluted tubule and collecting duct; however, physiological data regarding its role are limited. In this study, we investigated the role of Cx37 in fluid homeostasis using mice with a global deletion of Cx37 (Cx37-/- mice). Under baseline conditions, Cx37-/- had ~40% higher fluid intake associated with ~40% lower urine osmolality compared to wild-type (WT) mice. No differences were observed between genotypes in urinary adenosine triphosphate or prostaglandin E2, paracrine factors that alter renal water handling. After 18-hours of water deprivation, plasma aldosterone and urine osmolality increased significantly in Cx37-/- and WT mice; however, the latter remained ~375 mmol/kg lower in Cx37-/- mice, an effect associated with a more pronounced body weight loss despite higher urinary AVP/creatinine ratios compared to WT mice. Consistent with this, fluid intake in the first 3 hours after water deprivation was 37% greater in Cx37-/- vs WT mice. Cx37-/- mice showed significantly lower renal AQP2 abundance and AQP2 phosphorylation at serine 256 than WT mice in response to vehicle or dDAVP, suggesting a partial contribution of the kidney to the lower urine osmolality. The abundance and responses of the vasopressin V2 receptor, AQP3, NHE3, NKCC2, NCC, H+-ATPase, αENaC, γENaC or Na+/K+-ATPase were not significantly different between genotypes. In summary, these results demonstrate that Cx37 is important for body water handling.
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Affiliation(s)
- Jianxiang Xue
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Linto Thomas
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Jessica A. Dominguez Rieg
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | | | - Timo Rieg
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
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Effects of Ischemia-Reperfusion on Tubular Cell Membrane Transporters and Consequences in Kidney Transplantation. J Clin Med 2020; 9:jcm9082610. [PMID: 32806541 PMCID: PMC7464608 DOI: 10.3390/jcm9082610] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 07/31/2020] [Accepted: 08/06/2020] [Indexed: 12/12/2022] Open
Abstract
Ischemia-reperfusion (IR)-induced acute kidney injury (IRI) is an inevitable event in kidney transplantation. It is a complex pathophysiological process associated with numerous structural and metabolic changes that have a profound influence on the early and the late function of the transplanted kidney. Proximal tubular cells are particularly sensitive to IRI. These cells are involved in renal and whole-body homeostasis, detoxification processes and drugs elimination by a transporter-dependent, transcellular transport system involving Solute Carriers (SLCs) and ATP Binding Cassettes (ABCs) transporters. Numerous studies conducted mainly in animal models suggested that IRI causes decreased expression and activity of some major tubular transporters. This could favor uremic toxins accumulation and renal metabolic alterations or impact the pharmacokinetic/toxicity of drugs used in transplantation. It is of particular importance to understand the underlying mechanisms and effects of IR on tubular transporters in order to improve the mechanistic understanding of IRI pathophysiology, identify biomarkers of graft function or promote the design and development of novel and effective therapies. Modulation of transporters’ activity could thus be a new therapeutic opportunity to attenuate kidney injury during IR.
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25
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Thomas L, Xue J, Tomilin VN, Pochynyuk OM, Dominguez Rieg JA, Rieg T. PF-06869206 is a selective inhibitor of renal P i transport: evidence from in vitro and in vivo studies. Am J Physiol Renal Physiol 2020; 319:F541-F551. [PMID: 32744087 DOI: 10.1152/ajprenal.00146.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Plasma phosphate (Pi) levels are tightly controlled, and elevated plasma Pi levels are associated with an increased risk of cardiovascular complications and death. Two renal transport proteins mediate the majority of Pi reabsorption: Na+-phosphate cotransporters Npt2a and Npt2c, with Npt2a accounting for 70-80% of Pi reabsorption. The aim of the present study was to determine the in vitro effects of a novel Npt2a inhibitor (PF-06869206) in opossum kidney (OK) cells as well as determine its selectivity in vivo in Npt2a knockout (Npt2a-/-) mice. In OK cells, Npt2a inhibitor caused dose-dependent reductions of Na+-dependent Pi uptake (IC50: ~1.4 μmol/L), whereas the unselective Npt2 inhibitor phosphonoformic acid (PFA) resulted in an ~20% stronger inhibition of Pi uptake. The dose-dependent inhibitory effects were present after 24 h of incubation with both low- and high-Pi media. Michaelis-Menten kinetics in OK cells identified an ~2.4-fold higher Km for Pi in response to Npt2a inhibition with no significant change in apparent Vmax. Higher parathyroid hormone concentrations decreased Pi uptake equivalent to the maximal inhibitory effect of Npt2a inhibitor. In vivo, the Npt2a inhibitor induced a dose-dependent increase in urinary Pi excretion in wild-type mice (ED50: ~23 mg/kg), which was completely absent in Npt2a-/- mice, alongside a lack of decrease in plasma Pi. Of note, the Npt2a inhibitor-induced dose-dependent increase in urinary Na+ excretion was still present in Npt2a-/- mice, a response possibly mediated by an off-target acute inhibitory effect of the Npt2a inhibitor on open probability of the epithelial Na+ channel in the cortical collecting duct.
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Affiliation(s)
- Linto Thomas
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida
| | - Jianxiang Xue
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida
| | - Viktor N Tomilin
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas
| | - Oleh M Pochynyuk
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas
| | - Jessica A Dominguez Rieg
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida
| | - Timo Rieg
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida
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26
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Hu R, McDonough AA, Layton AT. Sex differences in solute transport along the nephrons: effects of Na + transport inhibition. Am J Physiol Renal Physiol 2020; 319:F487-F505. [PMID: 32744084 DOI: 10.1152/ajprenal.00240.2020] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Each day, ~1.7 kg of NaCl and 180 liters of water are reabsorbed by nephron segments in humans, with urinary excretion fine tuned to meet homeostatic requirements. These tasks are coordinated by a spectrum of renal Na+ transporters and channels. The goal of the present study was to investigate the extent to which inhibitors of transepithelial Na+ transport (TNa) along the nephron alter urinary solute excretion and how those effects may vary between male and female subjects. To accomplish that goal, we developed sex-specific multinephron models that represent detailed transcellular and paracellular transport processes along the nephrons of male and female rat kidneys. We simulated inhibition of Na+/H+ exchanger 3 (NHE3), bumetanide-sensitive Na+-K+-2Cl- cotransporter (NKCC2), Na+-Cl- cotransporter (NCC), and amiloride-sensitive epithelial Na+ channel (ENaC). NHE3 inhibition simulations predicted a substantially reduced proximal tubule TNa, and NKCC2 inhibition substantially reduced thick ascending limb TNa. Both gave rise to diuresis, natriuresis, and kaliuresis, with those effects stronger in female rats. While NCC inhibition was predicted to have only minor impact on renal TNa, it nonetheless had a notable effect of enhancing excretion of Na+, K+, and Cl-, particularly in female rats. Inhibition of ENaC was predicted to have opposite effects on the excretion of Na+ (increased) and K+ (decreased) and to have only a minor impact on whole kidney TNa. Unlike inhibition of other transporters, ENaC inhibition induced stronger natriuresis and diuresis in male rats than female rats. Overall, model predictions agreed well with measured changes in Na+ and K+ excretion in response to diuretics and Na+ transporter mutations.
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Affiliation(s)
- Rui Hu
- Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada
| | - Alicia A McDonough
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Anita T Layton
- Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, Canada.,Department of Biology, Cheriton School of Computer Science, and School of Pharmacology, University of Waterloo, Waterloo, Ontario, Canada
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27
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Tubular effects of sodium-glucose cotransporter 2 inhibitors: intended and unintended consequences. Curr Opin Nephrol Hypertens 2020; 29:523-530. [PMID: 32701600 DOI: 10.1097/mnh.0000000000000632] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
PURPOSE OF REVIEW Sodium-glucose cotransporter 2 (SGLT2) inhibitors are antihyperglycemic drugs that act by inhibiting renal sodium-glucose cotransport. Here we present new insights into 'off target', or indirect, effects of SGLT2 inhibitors. RECENT FINDINGS SGLT2 inhibition causes an acute increase in urinary glucose excretion. In addition to lowering blood glucose, there are several other effects that contribute to the overall beneficial renal and cardiovascular effects. Reabsorption of about 66% of sodium is accomplished in the proximal tubule and dependent on the sodium-hydrogen exchanger isoform 3 (NHE3). SGLT2 colocalizes with NHE3, and high glucose levels reduce NHE3 activity. The proximal tubule is also responsible for the majority of phosphate (Pi) reabsorption. SGLT2 inhibition is associated with increases in plasma Pi, fibroblast growth factor 23 and parathyroid hormone levels in nondiabetics and type 2 diabetes mellitus. Studies in humans identified a urate-lowering effect by SGLT2 inhibition which is possibly mediated by urate transporter 1 (URAT1) and/or glucose transporter member 9 in the proximal tubule. Of note, magnesium levels were also found to increase under SGLT2 inhibition, an effect that was preserved in nondiabetic patients with hypomagnesemia. SUMMARY Cardiorenal effects of SGLT2 inhibition might involve, in addition to direct effects on glucose homeostasis, effects on NHE3, phosphate, urate, and magnesium homeostasis.
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28
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An inducible intestinal epithelial cell-specific NHE3 knockout mouse model mimicking congenital sodium diarrhea. Clin Sci (Lond) 2020; 134:941-953. [PMID: 32227118 PMCID: PMC8819665 DOI: 10.1042/cs20200065] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 03/25/2020] [Accepted: 03/27/2020] [Indexed: 12/13/2022]
Abstract
The sodium–hydrogen exchanger isoform 3 (NHE3, SLC9A3) is abundantly expressed in the gastrointestinal tract and is proposed to play essential roles in Na+ and fluid absorption as well as acid–base homeostasis. Mutations in the SLC9A3 gene can cause congenital sodium diarrhea (CSD). However, understanding the precise role of intestinal NHE3 has been severely hampered due to the lack of a suitable animal model. To navigate this problem and better understand the role of intestinal NHE3, we generated a tamoxifen-inducible intestinal epithelial cell-specific NHE3 knockout mouse model (NHE3IEC-KO). Before tamoxifen administration, the phenotype and blood parameters of NHE3IEC-KO were unremarkable compared with control mice. After tamoxifen administration, NHE3IEC-KO mice have undetectable levels of NHE3 in the intestine. NHE3IEC-KO mice develop watery, alkaline diarrhea in combination with a swollen small intestine, cecum and colon. The persistent diarrhea results in higher fluid intake. After 3 weeks, NHE3IEC-KO mice show a ~25% mortality rate. The contribution of intestinal NHE3 to acid–base and Na+ homeostasis under normal conditions becomes evident in NHE3IEC-KO mice that have metabolic acidosis, lower blood bicarbonate levels, hyponatremia and hyperkalemia associated with drastically elevated plasma aldosterone levels. These results demonstrate that intestinal NHE3 has a significant contribution to acid–base, Na+ and volume homeostasis, and lack of intestinal NHE3 has consequences on intestinal structural integrity. This mouse model mimics and explains the phenotype of individuals with CSD carrying SLC9A3 mutations.
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29
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Fenton RA, Murali SK, Kaji I, Akiba Y, Kaunitz JD, Kristensen TB, Poulsen SB, Dominguez Rieg JA, Rieg T. Adenylyl Cyclase 6 Expression Is Essential for Cholera Toxin-Induced Diarrhea. J Infect Dis 2020; 220:1719-1728. [PMID: 30624615 DOI: 10.1093/infdis/jiz013] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 01/07/2019] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Cholera toxin (CT)-induced diarrhea is mediated by cyclic adenosine monophosphate (cAMP)-mediated active Cl- secretion via the cystic fibrosis transmembrane conductance regulator (CFTR). Although the constitutive activation of adenylyl cyclase (AC) in response to CT is due to adenosine diphosphate ribosylation of the small G protein α-subunit activating CFTR with consequent secretory diarrhea, the AC isoform(s) involved remain unknown. METHODS We generated intestinal epithelial cell-specific adenylyl cyclase 6 (AC6) knockout mice to study its role in CT-induced diarrhea. RESULTS AC6 messenger RNA levels were the highest of all 9 membrane-bound AC isoforms in mouse intestinal epithelial cells. Intestinal epithelial-specific AC6 knockout mice (AC6loxloxVillinCre) had undetectable AC6 levels in small intestinal and colonic epithelial cells. No significant differences in fluid and food intake, plasma electrolytes, intestinal/colon anatomy and morphology, or fecal water content were observed between genotypes. Nevertheless, CT-induced fluid accumulation in vivo was completely absent in AC6loxloxVillinCre mice, associated with a lack of forskolin- and CT-induced changes in the short-circuit current (ISC) of the intestinal mucosa, impaired cAMP generation in acutely isolated small intestinal epithelial cells, and significantly impaired apical CFTR levels in response to forskolin. CONCLUSIONS AC6 is a novel target for the treatment of CT-induced diarrhea.
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Affiliation(s)
| | - Sathish K Murali
- Department of Biomedicine, Aarhus University, Denmark.,University of South Florida, Tampa
| | - Izumi Kaji
- Greater Los Angeles VA Healthcare System, California.,Department of Medicine, University of California, Los Angeles
| | - Yasutada Akiba
- Greater Los Angeles VA Healthcare System, California.,Department of Medicine, University of California, Los Angeles
| | - Jonathan D Kaunitz
- Greater Los Angeles VA Healthcare System, California.,Department of Medicine, University of California, Los Angeles
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30
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Hoorn EJ, Gritter M, Cuevas CA, Fenton RA. Regulation of the Renal NaCl Cotransporter and Its Role in Potassium Homeostasis. Physiol Rev 2020; 100:321-356. [DOI: 10.1152/physrev.00044.2018] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Daily dietary potassium (K+) intake may be as large as the extracellular K+ pool. To avoid acute hyperkalemia, rapid removal of K+ from the extracellular space is essential. This is achieved by translocating K+ into cells and increasing urinary K+ excretion. Emerging data now indicate that the renal thiazide-sensitive NaCl cotransporter (NCC) is critically involved in this homeostatic kaliuretic response. This suggests that the early distal convoluted tubule (DCT) is a K+ sensor that can modify sodium (Na+) delivery to downstream segments to promote or limit K+ secretion. K+ sensing is mediated by the basolateral K+ channels Kir4.1/5.1, a capacity that the DCT likely shares with other nephron segments. Thus, next to K+-induced aldosterone secretion, K+ sensing by renal epithelial cells represents a second feedback mechanism to control K+ balance. NCC’s role in K+ homeostasis has both physiological and pathophysiological implications. During hypovolemia, NCC activation by the renin-angiotensin system stimulates Na+ reabsorption while preventing K+ secretion. Conversely, NCC inactivation by high dietary K+ intake maximizes kaliuresis and limits Na+ retention, despite high aldosterone levels. NCC activation by a low-K+ diet contributes to salt-sensitive hypertension. K+-induced natriuresis through NCC offers a novel explanation for the antihypertensive effects of a high-K+ diet. A possible role for K+ in chronic kidney disease is also emerging, as epidemiological data reveal associations between higher urinary K+ excretion and improved renal outcomes. This comprehensive review will embed these novel insights on NCC regulation into existing concepts of K+ homeostasis in health and disease.
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Affiliation(s)
- Ewout J. Hoorn
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Martin Gritter
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Catherina A. Cuevas
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Robert A. Fenton
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands; and Department of Biomedicine, Aarhus University, Aarhus, Denmark
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31
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Zhou C, Wang R, Jiang W, Zhu J, Liu Y, Zheng J, Wang X, Shang W, Sun L. Machine learning for the prediction of acute kidney injury and paraplegia after thoracoabdominal aortic aneurysm repair. J Card Surg 2019; 35:89-99. [PMID: 31765025 DOI: 10.1111/jocs.14317] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Chenyang Zhou
- Department of Cardiac Surgery Beijing Anzhen Hospital, Capital Medical University Beijing China
| | - Rong Wang
- Department of Cardiac Surgery Beijing Anzhen Hospital, Capital Medical University Beijing China
| | - Wenjian Jiang
- Department of Cardiac Surgery Beijing Anzhen Hospital, Capital Medical University Beijing China
| | - Junming Zhu
- Department of Cardiac Surgery Beijing Anzhen Hospital, Capital Medical University Beijing China
| | - Yongmin Liu
- Department of Cardiac Surgery Beijing Anzhen Hospital, Capital Medical University Beijing China
| | - Jun Zheng
- Department of Cardiac Surgery Beijing Anzhen Hospital, Capital Medical University Beijing China
| | - Xiaolong Wang
- Department of Cardiac Surgery Beijing Anzhen Hospital, Capital Medical University Beijing China
| | - Wei Shang
- Department of Cardiac Surgery Beijing Anzhen Hospital, Capital Medical University Beijing China
| | - Lizhong Sun
- Department of Cardiac Surgery Beijing Anzhen Hospital, Capital Medical University Beijing China
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32
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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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33
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Tomilin VN, Pochynyuk O. A peek into Epac physiology in the kidney. Am J Physiol Renal Physiol 2019; 317:F1094-F1097. [PMID: 31509013 DOI: 10.1152/ajprenal.00373.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
cAMP is a critical second messenger of numerous endocrine signals affecting water-electrolyte transport in the renal tubule. Exchange protein directly activated by cAMP (Epac) is a relatively recently discovered downstream effector of cAMP, having the same affinity to the second messenger as protein kinase A, the classical cAMP target. Two Epac isoforms, Epac1 and Epac2, are abundantly expressed in the renal epithelium, where they are thought to regulate water and electrolyte transport, particularly in the proximal tubule and collecting duct. Recent characterization of renal phenotype in mice lacking Epac1 and Epac2 revealed a critical role of the Epac signaling cascade in urinary concentration as well as in Na+ and urea excretion. In this review, we aim to critically summarize current knowledge of Epac relevance for renal function and to discuss the applicability of Epac-based strategies in the regulation of systemic water-electrolyte homeostasis.
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Affiliation(s)
- Viktor N Tomilin
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas
| | - Oleh Pochynyuk
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas
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34
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Banday AA, Diaz AD, Lokhandwala M. Kidney dopamine D 1-like receptors and angiotensin 1-7 interaction inhibits renal Na + transporters. Am J Physiol Renal Physiol 2019; 317:F949-F956. [PMID: 31411069 DOI: 10.1152/ajprenal.00135.2019] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The role of dopamine D1-like receptors (DR) in the regulation of renal Na+ transporters, natriuresis, and blood pressure is well established. However, the involvement of the angiotensin 1-7 (ANG 1-7)-Mas receptor in the regulation of Na+ balance and blood pressure is not clear. The present study aimed to investigate the hypothesis that ANG 1-7 can regulate Na+ homeostasis by modulating the renal dopamine system. Sprague-Dawley rats were infused with saline alone (vehicle) or saline with ANG 1-7, ANG 1-7 antagonist A-779, DR agonist SKF38393, and antagonist SCH23390. Infusion of ANG 1-7 caused significant natriuresis and diuresis compared with saline alone. Both natriuresis and diuresis were blocked by A-779 and SCH23390. SKF38393 caused a significant, SCH23390-sensitive natriuresis and diuresis, and A-779 had no effect on the SKF38393 response. Concomitant infusion of ANG 1-7 and SKF38393 did not show a cumulative effect compared with either agonist alone. Treatment of renal proximal tubules with ANG 1-7 or SKF38393 caused a significant decrease in Na+-K+-ATPase and Na+/H+ exchanger isoform 3 activity. While SCH23390 blocked both ANG 1-7- and SKF38393-induced inhibition, the DR response was not sensitive to A-779. Additionally, ANG 1-7 activated PKG, enhanced tyrosine hydroxylase activity via Ser40 phosphorylation, and increased renal dopamine production. These data suggest that ANG 1-7, via PKG, enhances tyrosine hydroxylase activity, which increases renal dopamine production and activation of DR and subsequent natriuresis. This study provides evidence for a unidirectional functional interaction between two G protein-coupled receptors to regulate renal Na+ transporters and induce natriuresis.
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Affiliation(s)
- Anees A Banday
- University of Houston, College of Pharmacy, Heart and Kidney Institute, Houston, Texas
| | - Andrea Diaz Diaz
- University of Houston, College of Pharmacy, Heart and Kidney Institute, Houston, Texas.,School of Pharmacy, University College Cork, Cork, Ireland
| | - Mustafa Lokhandwala
- University of Houston, College of Pharmacy, Heart and Kidney Institute, Houston, Texas
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35
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Thomas L, Xue J, Murali SK, Fenton RA, Dominguez Rieg JA, Rieg T. Pharmacological Npt2a Inhibition Causes Phosphaturia and Reduces Plasma Phosphate in Mice with Normal and Reduced Kidney Function. J Am Soc Nephrol 2019; 30:2128-2139. [PMID: 31409727 DOI: 10.1681/asn.2018121250] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 07/14/2019] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND The kidneys play an important role in phosphate homeostasis. Patients with CKD develop hyperphosphatemia in the later stages of the disease. Currently, treatment options are limited to dietary phosphate restriction and oral phosphate binders. The sodium-phosphate cotransporter Npt2a, which mediates a large proportion of phosphate reabsorption in the kidney, might be a good therapeutic target for new medications for hyperphosphatemia. METHODS The authors assessed the effects of the first orally bioavailable Npt2a inhibitor (Npt2a-I) PF-06869206 in normal mice and mice that had undergone subtotal nephrectomy (5/6 Nx), a mouse model of CKD. Dose-response relationships of sodium, chloride, potassium, phosphate, and calcium excretion were assessed in response to the Npt2a inhibitor in both groups of mice. Expression and localization of Npt2a/c and levels of plasma phosphate, calcium, parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF-23) were studied up to 24-hours after Npt2a-I treatment. RESULTS In normal mice, Npt2a inhibition caused a dose-dependent increase in urinary phosphate (ED50 approximately 21 mg/kg), calcium, sodium and chloride excretion. In contrast, urinary potassium excretion, flow rate and urinary pH were not affected dose dependently. Plasma phosphate and PTH significantly decreased after 3 hours, with both returning to near baseline levels after 24 hours. Similar effects were observed in the mouse model of CKD but were reduced in magnitude. CONCLUSIONS Npt2a inhibition causes a dose-dependent increase in phosphate, sodium and chloride excretion associated with reductions in plasma phosphate and PTH levels in normal mice and in a CKD mouse model.
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Affiliation(s)
- Linto Thomas
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida; and
| | - Jianxiang Xue
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida; and
| | | | - Robert A Fenton
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Jessica A Dominguez Rieg
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida; and
| | - Timo Rieg
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida; and
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Onishi A, Fu Y, Darshi M, Crespo-Masip M, Huang W, Song P, Patel R, Kim YC, Nespoux J, Freeman B, Soleimani M, Thomson S, Sharma K, Vallon V. Effect of renal tubule-specific knockdown of the Na +/H + exchanger NHE3 in Akita diabetic mice. Am J Physiol Renal Physiol 2019; 317:F419-F434. [PMID: 31166707 PMCID: PMC6732454 DOI: 10.1152/ajprenal.00497.2018] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 05/21/2019] [Accepted: 05/27/2019] [Indexed: 01/03/2023] Open
Abstract
Na+/H+ exchanger isoform 3 (NHE3) contributes to Na+/bicarbonate reabsorption and ammonium secretion in early proximal tubules. To determine its role in the diabetic kidney, type 1 diabetic Akita mice with tubular NHE3 knockdown [Pax8-Cre; NHE3-knockout (KO) mice] were generated. NHE3-KO mice had higher urine pH, more bicarbonaturia, and compensating increases in renal mRNA expression for genes associated with generation of ammonium, bicarbonate, and glucose (phosphoenolpyruvate carboxykinase) in proximal tubules and H+ and ammonia secretion and glycolysis in distal tubules. This left blood pH and bicarbonate unaffected in nondiabetic and diabetic NHE3-KO versus wild-type mice but was associated with renal upregulation of proinflammatory markers. Higher renal phosphoenolpyruvate carboxykinase expression in NHE3-KO mice was associated with lower Na+-glucose cotransporter (SGLT)2 and higher SGLT1 expression, indicating a downward tubular shift in Na+ and glucose reabsorption. NHE3-KO was associated with lesser kidney weight and glomerular filtration rate (GFR) independent of diabetes and prevented diabetes-associated albuminuria. NHE3-KO, however, did not attenuate hyperglycemia or prevent diabetes from increasing kidney weight and GFR. Higher renal gluconeogenesis may explain similar hyperglycemia despite lower SGLT2 expression and higher glucosuria in diabetic NHE3-KO versus wild-type mice; stronger SGLT1 engagement could have affected kidney weight and GFR responses. Chronic kidney disease in humans is associated with reduced urinary excretion of metabolites of branched-chain amino acids and the tricarboxylic acid cycle, a pattern mimicked in diabetic wild-type mice. This pattern was reversed in nondiabetic NHE3-KO mice, possibly reflecting branched-chain amino acids use for ammoniagenesis and tricarboxylic acid cycle upregulation to support formation of ammonia, bicarbonate, and glucose in proximal tubule. NHE3-KO, however, did not prevent the diabetes-induced urinary downregulation in these metabolites.
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Affiliation(s)
- Akira Onishi
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Yiling Fu
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Manjula Darshi
- Center for Renal Precision Medicine, University of Texas Health San Antonio, San Antonio, Texas
| | - Maria Crespo-Masip
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
- Biomedical Research Institute (IRBLleida), University of Lleida, Lleida, Spain
| | - Winnie Huang
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Panai Song
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Rohit Patel
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Young Chul Kim
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Josselin Nespoux
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Brent Freeman
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | | | - Scott Thomson
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Kumar Sharma
- Center for Renal Precision Medicine, University of Texas Health San Antonio, San Antonio, Texas
| | - Volker Vallon
- Department of Medicine, University of California San Diego and Veterans Affairs San Diego Healthcare System, San Diego, California
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37
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Li XC, Zhu D, Chen X, Zheng X, Zhao C, Zhang J, Soleimani M, Rubera I, Tauc M, Zhou X, Zhuo JL. Proximal Tubule-Specific Deletion of the NHE3 (Na +/H + Exchanger 3) in the Kidney Attenuates Ang II (Angiotensin II)-Induced Hypertension in Mice. Hypertension 2019; 74:526-535. [PMID: 31352824 DOI: 10.1161/hypertensionaha.119.13094] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The present study directly tested the hypothesis that the NHE3 (Na+/H+ exchanger 3) in the proximal tubules of the kidney is required for the development of Ang II (angiotensin II)-induced hypertension using PT-Nhe3-/- (proximal tubule-specific NHE3 knockout) mice. Specifically, PT-Nhe3-/- mice were generated using the SGLT2-Cre/Nhe3loxlox approach, whereas Ang II-induced hypertension was studied in 12 groups (n=5-12 per group) of adult male and female wild-type (WT) and PT-Nhe3-/- mice. Under basal conditions, systolic blood pressure, diastolic blood pressure, and mean arterial blood pressure were significantly lower in male and female PT-Nhe3-/- than WT mice (P<0.01). A high pressor, 1.5 mg/kg per day, intraperitoneal or a slow pressor dose of Ang II, 0.5 mg/kg per day, intraperitoneal for 2 weeks significantly increased systolic blood pressure, diastolic blood pressure, and mean arterial blood pressure in male and female WT mice (P<0.01), but the hypertensive response to Ang II was markedly attenuated in male and female PT-Nhe3-/- mice (P<0.01). Ang II impaired the pressure-natriuresis response in WT mice, whereas proximal tubule-specific deletion of NHE3 improved the pressure-natriuresis response in Ang II-infused PT-Nhe3-/- mice (P<0.01). AT1 receptor blocker losartan completely blocked Ang II-induced hypertension in both WT and PT-Nhe3-/- mice (P<0.01). However, inhibition of nitric oxide synthase with L-NG-Nitroarginine methyl ester had no effect on Ang II-induced hypertension in WT or PT-Nhe3-/- mice (not significant). Furthermore, Ang II-induced hypertension was significantly attenuated by an orally absorbable NHE3 inhibitor AVE0657. In conclusion, NHE3 in the proximal tubules of the kidney may be a therapeutical target in hypertension induced by Ang II or with increased NHE3 expression in the proximal tubules.
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Affiliation(s)
- Xiao C Li
- From the Department of Pharmacology and Toxicology (X.C.L., D.Z., X.C., X. Zheng, C.Z., J.Z., J.L.Z.), University of Mississippi Medical Center, Jackson
- Division of Nephrology, Department of Medicine (X.C.L., J.L.Z.), University of Mississippi Medical Center, Jackson
| | - Dongmin Zhu
- From the Department of Pharmacology and Toxicology (X.C.L., D.Z., X.C., X. Zheng, C.Z., J.Z., J.L.Z.), University of Mississippi Medical Center, Jackson
- Department of Anesthesiology, Shenzhen Far East Obstetrics and Gynecology Hospital, China (D.Z.)
| | - Xu Chen
- From the Department of Pharmacology and Toxicology (X.C.L., D.Z., X.C., X. Zheng, C.Z., J.Z., J.L.Z.), University of Mississippi Medical Center, Jackson
| | - Xiaowen Zheng
- From the Department of Pharmacology and Toxicology (X.C.L., D.Z., X.C., X. Zheng, C.Z., J.Z., J.L.Z.), University of Mississippi Medical Center, Jackson
- Department of Emergency Medicine, Second Affiliated Hospital, Guangxi Medical University, Nanning, China (X. Zheng, C.Z., J.Z.)
| | - Chunling Zhao
- From the Department of Pharmacology and Toxicology (X.C.L., D.Z., X.C., X. Zheng, C.Z., J.Z., J.L.Z.), University of Mississippi Medical Center, Jackson
- Department of Emergency Medicine, Second Affiliated Hospital, Guangxi Medical University, Nanning, China (X. Zheng, C.Z., J.Z.)
| | - Jianfeng Zhang
- From the Department of Pharmacology and Toxicology (X.C.L., D.Z., X.C., X. Zheng, C.Z., J.Z., J.L.Z.), University of Mississippi Medical Center, Jackson
- Department of Emergency Medicine, Second Affiliated Hospital, Guangxi Medical University, Nanning, China (X. Zheng, C.Z., J.Z.)
| | - Manoocher Soleimani
- Division of Nephrology and Hypertension, Department of Internal Medicine, The University of Cincinnati College of Medicine, OH (M.S.)
| | - Isabelle Rubera
- Laboratoire de Physiomédecine Moléculaire, LP2M, UMR-CNRS 7370, Université Côte d'Azur, Nice Cedex 2, France (I.R., M.T.)
| | - Michel Tauc
- Laboratoire de Physiomédecine Moléculaire, LP2M, UMR-CNRS 7370, Université Côte d'Azur, Nice Cedex 2, France (I.R., M.T.)
| | - Xinchun Zhou
- Department of Pathology (X. Zhou), University of Mississippi Medical Center, Jackson
| | - Jia L Zhuo
- From the Department of Pharmacology and Toxicology (X.C.L., D.Z., X.C., X. Zheng, C.Z., J.Z., J.L.Z.), University of Mississippi Medical Center, Jackson
- Division of Nephrology, Department of Medicine (X.C.L., J.L.Z.), University of Mississippi Medical Center, Jackson
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Li XC, Soleimani M, Zhu D, Rubera I, Tauc M, Zheng X, Zhang J, Chen X, Zhuo JL. Proximal Tubule-Specific Deletion of the NHE3 (Na +/H + Exchanger 3) Promotes the Pressure-Natriuresis Response and Lowers Blood Pressure in Mice. Hypertension 2019; 72:1328-1336. [PMID: 30571224 DOI: 10.1161/hypertensionaha.118.10884] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The present study directly tested the hypothesis that deletion of the NHE3 (Na+/H+ exchanger 3) selectively in the proximal tubules of the kidney lowers basal blood pressure by increasing the pressure-natriuresis response in mice. Adult male and female, age-matched wild-type (WT) littermates and proximal tubule-specific NHE3 knockout mice (PT- Nhe3-/-; n=6-16 per group) were studied for (1) basal phenotypes of electrolytes and pH, blood pressure, and kidney function; (2) the pressure-natriuresis response using the mesenteric, celiac, and abdominal arterial occlusion technique; and (3) the natriuretic responses to acute saline expansion (0.9% NaCl, 10% body weight, intraperitoneal) or 2-week of 2% NaCl diet. Under basal conditions, PT- Nhe3-/- mice showed significantly lower systolic, diastolic, and mean arterial blood pressure ( P<0.01) than WT mice ( P<0.01). PT- Nhe3-/- mice also exhibited significantly greater diuretic ( P<0.01) and natriuretic responses than WT mice ( P<0.01), without altering 24-hour fecal Na+ excretion, plasma pH, Na+, and bicarbonate levels. In response to increased renal perfusion pressure by 30 mm Hg, the pressure-natriuresis response increased 5-fold in WT mice ( P<0.01), but it increased 8-fold in PT- Nhe3-/- mice ( P<0.01). In response to 10% acute saline expansion or 2-week 2% NaCl diet, more pronounced natriuretic responses were demonstrated in PT- Nhe3-/- than WT mice ( P<0.01). Our results support the scientific premise and physiological relevance that NHE3 in the proximal tubules plays an essential role in maintaining basal blood pressure homeostasis, and genetic deletion of NHE3 selectively in the proximal tubules of the kidney lowers blood pressure by increasing the pressure natriuretic response.
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Affiliation(s)
- Xiao C Li
- From the Division of Nephrology, Department of Pharmacology and Toxicology and Department of Medicine, University of Mississippi Medical Center, Jackson (X.C.L., X.Z., J.Z., X.C., J.L.Z.)
| | - Manoocher Soleimani
- Division of Nephrology and Hypertension, Department of Internal Medicine, The University of Cincinnati College of Medicine, OH (M.S.)
| | - Dongmin Zhu
- Department of Outpatients, Guangxi Science and Technology University No. 1 Affiliated Hospital, Liuzhou, China (D.Z.)
| | - Isabelle Rubera
- Laboratoire Centre National de la Recherche Scientifique (CNRS) 3472 LP2M, Université de Nice Sophia Antipolis, Nice Cedex 2, France (I.R., M.T.)
| | - Michel Tauc
- Laboratoire Centre National de la Recherche Scientifique (CNRS) 3472 LP2M, Université de Nice Sophia Antipolis, Nice Cedex 2, France (I.R., M.T.)
| | - Xiaowen Zheng
- From the Division of Nephrology, Department of Pharmacology and Toxicology and Department of Medicine, University of Mississippi Medical Center, Jackson (X.C.L., X.Z., J.Z., X.C., J.L.Z.).,Department of Emergency Medicine, Second Affiliated Hospital, Guangxi Medical University, Nanning, China (X.Z., J.Z.)
| | - Jianfeng Zhang
- From the Division of Nephrology, Department of Pharmacology and Toxicology and Department of Medicine, University of Mississippi Medical Center, Jackson (X.C.L., X.Z., J.Z., X.C., J.L.Z.)
| | - Xu Chen
- From the Division of Nephrology, Department of Pharmacology and Toxicology and Department of Medicine, University of Mississippi Medical Center, Jackson (X.C.L., X.Z., J.Z., X.C., J.L.Z.)
| | - Jia L Zhuo
- From the Division of Nephrology, Department of Pharmacology and Toxicology and Department of Medicine, University of Mississippi Medical Center, Jackson (X.C.L., X.Z., J.Z., X.C., J.L.Z.).,Department of Emergency Medicine, Second Affiliated Hospital, Guangxi Medical University, Nanning, China (X.Z., J.Z.)
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39
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Li XC, Zheng X, Chen X, Zhao C, Zhu D, Zhang J, Zhuo JL. Genetic and genomic evidence for an important role of the Na +/H + exchanger 3 in blood pressure regulation and angiotensin II-induced hypertension. Physiol Genomics 2019; 51:97-108. [PMID: 30849009 DOI: 10.1152/physiolgenomics.00122.2018] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The sodium (Na+)/hydrogen (H+) exchanger 3 (NHE3) and sodium-potassium adenosine triphosphatase (Na+/K+-ATPase) are two of the most important Na+ transporters in the proximal tubules of the kidney. On the apical membrane side, NHE3 primarily mediates the entry of Na+ into and the exit of H+ from the proximal tubules, directly and indirectly being responsible for reabsorbing ~50% of filtered Na+ in the proximal tubules of the kidney. On the basolateral membrane side, Na+/K+-ATPase serves as a powerful engine driving Na+ out of, while pumping K+ into the proximal tubules against their concentration gradients. While the roles of NHE3 and Na+/K+-ATPase in proximal tubular Na+ transport under in vitro conditions are well recognized, their respective contributions to the basal blood pressure regulation and angiotensin II (ANG II)-induced hypertension remain poorly understood. Recently, we have been fortunate to be able to use genetically modified mouse models with global, kidney- or proximal tubule-specific deletion of NHE3 to directly determine the cause and effect relationship between NHE3, basal blood pressure homeostasis, and ANG II-induced hypertension at the whole body, kidney and/or proximal tubule levels. The purpose of this article is to review the genetic and genomic evidence for an important role of NHE3 with a focus in the regulation of basal blood pressure and ANG II-induced hypertension, as we learned from studies using global, kidney- or proximal tubule-specific NHE3 knockout mice. We hypothesize that NHE3 in the proximal tubules is necessary for maintaining basal blood pressure homeostasis and the development of ANG II-induced hypertension.
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Affiliation(s)
- Xiao C Li
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Internal Medicine; Cardiovascular and Renal Research Center; The University of Mississippi Medical Center , Jackson, Mississippi
| | - Xiaowen Zheng
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Internal Medicine; Cardiovascular and Renal Research Center; The University of Mississippi Medical Center , Jackson, Mississippi
| | - Xu Chen
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Internal Medicine; Cardiovascular and Renal Research Center; The University of Mississippi Medical Center , Jackson, Mississippi
| | - Chunling Zhao
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Internal Medicine; Cardiovascular and Renal Research Center; The University of Mississippi Medical Center , Jackson, Mississippi
| | - Dongmin Zhu
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Internal Medicine; Cardiovascular and Renal Research Center; The University of Mississippi Medical Center , Jackson, Mississippi
| | - Jianfeng Zhang
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Internal Medicine; Cardiovascular and Renal Research Center; The University of Mississippi Medical Center , Jackson, Mississippi
| | - Jia L Zhuo
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology; Division of Nephrology, Internal Medicine; Cardiovascular and Renal Research Center; The University of Mississippi Medical Center , Jackson, Mississippi
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Saurette M, Alexander RT. Intestinal phosphate absorption: The paracellular pathway predominates? Exp Biol Med (Maywood) 2019; 244:646-654. [PMID: 30764666 DOI: 10.1177/1535370219831220] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
IMPACT STATEMENT This review summarizes the work on transcellular intestinal phosphate absorption, arguing why this pathway is not the predominant pathway in humans consuming a "Western" diet. We then highlight the recent evidence which is strongly consistent with paracellular intestinal phosphate absorption mediating the bulk of intestinal phosphate absorption in humans.
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Affiliation(s)
- Matthew Saurette
- 1 Department of Physiology, University of Alberta, Edmonton, Alberta T6G 2R7, Canada.,2 The Women's & Children's Health Research Institute, Edmonton, Alberta T6G 1C9, Canada
| | - R Todd Alexander
- 1 Department of Physiology, University of Alberta, Edmonton, Alberta T6G 2R7, Canada.,2 The Women's & Children's Health Research Institute, Edmonton, Alberta T6G 1C9, Canada.,3 Department of Pediatrics, University of Alberta, Edmonton, Alberta T6G 2R7, Canada
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Cherezova A, Tomilin V, Buncha V, Zaika O, Ortiz PA, Mei F, Cheng X, Mamenko M, Pochynyuk O. Urinary concentrating defect in mice lacking Epac1 or Epac2. FASEB J 2019; 33:2156-2170. [PMID: 30252533 PMCID: PMC6338637 DOI: 10.1096/fj.201800435r] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 08/27/2018] [Indexed: 11/11/2022]
Abstract
cAMP is a universal second messenger regulating a plethora of processes in the kidney. Two downstream effectors of cAMP are PKA and exchange protein directly activated by cAMP (Epac), which, unlike PKA, is often linked to elevation of [Ca2+]i. While both Epac isoforms (Epac1 and Epac2) are expressed along the nephron, their relevance in the kidney remains obscure. We combined ratiometric calcium imaging with quantitative immunoblotting, immunofluorescent confocal microscopy, and balance studies in mice lacking Epac1 or Epac2 to determine the role of Epac in renal water-solute handling. Epac1-/- and Epac2-/- mice developed polyuria despite elevated arginine vasopressin levels. We did not detect major deficiencies in arginine vasopressin [Ca2+]i signaling in split-opened collecting ducts or decreases in aquaporin water channel type 2 levels. Instead, sodium-hydrogen exchanger type 3 levels in the proximal tubule were dramatically reduced in Epac1-/- and Epac2-/- mice. Water deprivation revealed persisting polyuria, impaired urinary concentration ability, and augmented urinary excretion of Na+ and urea in both mutant mice. In summary, we report a nonredundant contribution of Epac isoforms to renal function. Deletion of Epac1 and Epac2 decreases sodium-hydrogen exchanger type 3 expression in the proximal tubule, leading to polyuria and osmotic diuresis.-Cherezova, A., Tomilin, V., Buncha, V., Zaika, O., Ortiz, P. A., Mei, F., Cheng, X., Mamenko, M., Pochynyuk, O. Urinary concentrating defect in mice lacking Epac1 or Epac2.
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Affiliation(s)
- Alena Cherezova
- Department of Physiology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Viktor Tomilin
- Department of Integrative Biology and Pharmacology The University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Vadym Buncha
- Department of Physiology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Oleg Zaika
- Department of Integrative Biology and Pharmacology The University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Pablo A. Ortiz
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan, USA; and
| | - Fang Mei
- Department of Integrative Biology and Pharmacology The University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Xiaodong Cheng
- Department of Integrative Biology and Pharmacology The University of Texas Health Science Center at Houston, Houston, Texas, USA
- Texas Therapeutics Institute, The University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Mykola Mamenko
- Department of Physiology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Oleh Pochynyuk
- Department of Integrative Biology and Pharmacology The University of Texas Health Science Center at Houston, Houston, Texas, USA
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Thomas L, Xue J, Dominguez Rieg JA, Rieg T. Contribution of NHE3 and dietary phosphate to lithium pharmacokinetics. Eur J Pharm Sci 2018; 128:1-7. [PMID: 30419292 DOI: 10.1016/j.ejps.2018.11.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 10/09/2018] [Accepted: 11/08/2018] [Indexed: 01/13/2023]
Abstract
Lithium is one of the mainstays for the treatment of bipolar disorder despite its side effects on the endocrine, neurological, and renal systems. Experimentally, lithium has been used as a measure to determine proximal tubule reabsorption based on the assumption that lithium and sodium transport go in parallel in the proximal tubule. However, the exact mechanism by which lithium is reabsorbed remains elusive. The majority of proximal tubule sodium reabsorption is directly or indirectly mediated by the sodium-hydrogen exchanger 3 (NHE3). In addition, sodium-phosphate cotransporters have been implicated in renal lithium reabsorption. In order to better understand the role of sodium-phosphate cotransporters involved in lithium (re)absorption, we studied lithium pharmacokinetics in: i) tubule-specific NHE3 knockout mice (NHE3loxloxPax8Cre), and ii) mice challenged with low or high phosphate diets. Intravenous or oral administration of lithium did not result in differences in lithium bioavailability, half-life, maximum plasma concentrations, area under the curve, lithium clearance, or urinary lithium/creatinine ratios between control and NHE3loxloxPax8Cre mice. After one week of dietary phosphate challenges, lithium bioavailability was ~30% lower on low versus high dietary phosphate, possibly the consequence of a smaller area under the curve after oral administration. This was associated with higher apparent lithium clearance after oral administration and lower urinary lithium/creatinine ratios on low versus high dietary phosphate. Collectively, renal NHE3 does not play a role in lithium pharmacokinetics; however, dietary phosphate could have an indirect effect on lithium bioavailability and lithium disposition.
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Affiliation(s)
- Linto Thomas
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL 33612, USA
| | - Jianxiang Xue
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL 33612, USA
| | - Jessica A Dominguez Rieg
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL 33612, USA
| | - Timo Rieg
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL 33612, USA.
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Nawata CM, Pannabecker TL. Mammalian urine concentration: a review of renal medullary architecture and membrane transporters. J Comp Physiol B 2018; 188:899-918. [PMID: 29797052 PMCID: PMC6186196 DOI: 10.1007/s00360-018-1164-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 04/23/2018] [Accepted: 05/14/2018] [Indexed: 01/10/2023]
Abstract
Mammalian kidneys play an essential role in balancing internal water and salt concentrations. When water needs to be conserved, the renal medulla produces concentrated urine. Central to this process of urine concentration is an osmotic gradient that increases from the corticomedullary boundary to the inner medullary tip. How this gradient is generated and maintained has been the subject of study since the 1940s. While it is generally accepted that the outer medulla contributes to the gradient by means of an active process involving countercurrent multiplication, the source of the gradient in the inner medulla is unclear. The last two decades have witnessed advances in our understanding of the urine-concentrating mechanism. Details of medullary architecture and permeability properties of the tubules and vessels suggest that the functional and anatomic relationships of these structures may contribute to the osmotic gradient necessary to concentrate urine. Additionally, we are learning more about the membrane transporters involved and their regulatory mechanisms. The role of medullary architecture and membrane transporters in the mammalian urine-concentrating mechanism are the focus of this review.
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Affiliation(s)
- C Michele Nawata
- Department of Physiology, Banner University Medical Center, University of Arizona, 1501 N. Campbell Avenue, Tucson, AZ, 85724-5051, USA.
| | - Thomas L Pannabecker
- Department of Physiology, Banner University Medical Center, University of Arizona, 1501 N. Campbell Avenue, Tucson, AZ, 85724-5051, USA
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Adenylyl cyclase 6 is required for maintaining acid-base homeostasis. Clin Sci (Lond) 2018; 132:1779-1796. [PMID: 29941522 DOI: 10.1042/cs20180060] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Revised: 06/15/2018] [Accepted: 06/25/2018] [Indexed: 12/14/2022]
Abstract
Adenylyl cyclase (AC) isoform 6 (AC6) is highly expressed throughout the renal tubule and collecting duct (CD), catalyzes the synthesis of cAMP and contributes to various aspects of renal transport. Several proteins involved in acid-base homeostasis are regulated by cAMP. In the present study, we assess the relative contribution of AC6 to overall acid-base regulation using mice with global deletion of AC6 (AC6-/-) or newly generated mice lacking AC6 in the renal tubule and CD (AC6loxloxPax8Cre). Higher energy expenditure in AC6-/- relative to wild-type (WT) mice, was associated with lower urinary pH, mild alkalosis in conjunction with elevated blood HCO3- concentrations, and significantly higher renal abundance of the H+-ATPase B1 subunit. In contrast with WT mice, AC6-/- mice have a less pronounced increase in urinary pH after 8 days of HCO3- challenge, which is associated with increased blood pH and HCO3- concentrations. Immunohistochemistry demonstrated that AC6 was expressed in intercalated cells (IC), but subcellular distribution of the H+-ATPase B1 subunit, pendrin, and the anion exchangers 1 and 2 in AC6-/- mice was normal. In the AC6-/- mice, H+-ATPase B1 subunit levels after HCO3- challenge were greater, which correlated with a higher number of type A IC. In contrast with the AC6-/- mice, AC6loxloxPax8Cre mice had normal urinary pH under baseline conditions but higher blood HCO3- than controls after HCO3- challenge. In conclusion, AC6 is required for maintaining normal acid-base homeostasis and energy expenditure. Under baseline conditions, renal AC6 is redundant for acid-base balance but becomes important under alkaline conditions.
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Taub M. Gene Level Regulation of Na,K-ATPase in the Renal Proximal Tubule Is Controlled by Two Independent but Interacting Regulatory Mechanisms Involving Salt Inducible Kinase 1 and CREB-Regulated Transcriptional Coactivators. Int J Mol Sci 2018; 19:E2086. [PMID: 30021947 PMCID: PMC6073390 DOI: 10.3390/ijms19072086] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Revised: 07/13/2018] [Accepted: 07/16/2018] [Indexed: 12/26/2022] Open
Abstract
For many years, studies concerning the regulation of Na,K-ATPase were restricted to acute regulatory mechanisms, which affected the phosphorylation of Na,K-ATPase, and thus its retention on the plasma membrane. However, in recent years, this focus has changed. Na,K-ATPase has been established as a signal transducer, which becomes part of a signaling complex as a consequence of ouabain binding. Na,K-ATPase within this signaling complex is localized in caveolae, where Na,K-ATPase has also been observed to regulate Inositol 1,4,5-Trisphosphate Receptor (IP3R)-mediated calcium release. This latter association has been implicated as playing a role in signaling by G Protein Coupled Receptors (GPCRs). Here, the consequences of signaling by renal effectors that act via such GPCRs are reviewed, including their regulatory effects on Na,K-ATPase gene expression in the renal proximal tubule (RPT). Two major types of gene regulation entail signaling by Salt Inducible Kinase 1 (SIK1). On one hand, SIK1 acts so as to block signaling via cAMP Response Element (CRE) Binding Protein (CREB) Regulated Transcriptional Coactivators (CRTCs) and on the other hand, SIK1 acts so as to stimulate signaling via the Myocyte Enhancer Factor 2 (MEF2)/nuclear factor of activated T cell (NFAT) regulated genes. Ultimate consequences of these pathways include regulatory effects which alter the rate of transcription of the Na,K-ATPase β1 subunit gene atp1b1 by CREB, as well as by MEF2/NFAT.
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Affiliation(s)
- Mary Taub
- Biochemistry Dept., Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, 955 Main Street, Suite 4902, Buffalo, NY 14203, USA.
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Aw M, Armstrong TM, Nawata CM, Bodine SN, Oh JJ, Wei G, Evans KK, Shahidullah M, Rieg T, Pannabecker TL. Body mass-specific Na +-K +-ATPase activity in the medullary thick ascending limb: implications for species-dependent urine concentrating mechanisms. Am J Physiol Regul Integr Comp Physiol 2018; 314:R563-R573. [PMID: 29351422 DOI: 10.1152/ajpregu.00289.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In general, the mammalian whole body mass-specific metabolic rate correlates positively with maximal urine concentration (Umax) irrespective of whether or not the species have adapted to arid or mesic habitat. Accordingly, we hypothesized that the thick ascending limb (TAL) of a rodent with markedly higher whole body mass-specific metabolism than rat exhibits a substantially higher TAL metabolic rate as estimated by Na+-K+-ATPase activity and Na+-K+-ATPase α1-gene and protein expression. The kangaroo rat inner stripe of the outer medulla exhibits significantly higher mean Na+-K+-ATPase activity (~70%) compared with two rat strains (Sprague-Dawley and Munich-Wistar), extending prior studies showing rat activity exceeds rabbit. Furthermore, higher expression of Na+-K+-ATPase α1-protein (~4- to 6-fold) and mRNA (~13-fold) and higher TAL mitochondrial volume density (~20%) occur in the kangaroo rat compared with both rat strains. Rat TAL Na+-K+-ATPase α1-protein expression is relatively unaffected by body hydration status or, shown previously, by dietary Na+, arguing against confounding effects from two unavoidably dissimilar diets: grain-based diet without water (kangaroo rat) or grain-based diet with water (rat). We conclude that higher TAL Na+-K+-ATPase activity contributes to relationships between whole body mass-specific metabolic rate and high Umax. More vigorous TAL Na+-K+-ATPase activity in kangaroo rat than rat may contribute to its steeper Na+ and urea axial concentration gradients, adding support to a revised model of the urine concentrating mechanism, which hypothesizes a leading role for vigorous active transport of NaCl, rather than countercurrent multiplication, in generating the outer medullary axial osmotic gradient.
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Affiliation(s)
- Mun Aw
- Department of Physiology, Banner-University Medical Center, University of Arizona , Tucson, Arizona
| | - Tamara M Armstrong
- Department of Physiology, Banner-University Medical Center, University of Arizona , Tucson, Arizona
| | - C Michele Nawata
- Department of Physiology, Banner-University Medical Center, University of Arizona , Tucson, Arizona
| | - Sarah N Bodine
- Department of Physiology, Banner-University Medical Center, University of Arizona , Tucson, Arizona
| | - Jeeeun J Oh
- Department of Physiology, Banner-University Medical Center, University of Arizona , Tucson, Arizona
| | - Guojun Wei
- Department of Physiology, Banner-University Medical Center, University of Arizona , Tucson, Arizona
| | - Kristen K Evans
- Department of Physiology, Banner-University Medical Center, University of Arizona , Tucson, Arizona
| | - Mohammad Shahidullah
- Department of Physiology, Banner-University Medical Center, University of Arizona , Tucson, Arizona
| | - Timo Rieg
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Thomas L Pannabecker
- Department of Physiology, Banner-University Medical Center, University of Arizona , Tucson, Arizona
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