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Staruschenko A, Alexander RT, Caplan MJ, Ilatovskaya DV. Calcium signalling and transport in the kidney. Nat Rev Nephrol 2024:10.1038/s41581-024-00835-z. [PMID: 38641658 DOI: 10.1038/s41581-024-00835-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/27/2024] [Indexed: 04/21/2024]
Abstract
The kidney plays a pivotal role in regulating calcium levels within the body. Approximately 98% of the filtered calcium is reabsorbed in the nephron, and this process is tightly controlled to maintain calcium homeostasis, which is required to facilitate optimal bone mineralization, preserve serum calcium levels within a narrow range, and support intracellular signalling mechanisms. The maintenance of these functions is attributed to a delicate balance achieved by various calcium channels, transporters, and calcium-binding proteins in renal cells. Perturbation of this balance due to deficiency or dysfunction of calcium channels and calcium-binding proteins can lead to severe complications. For example, polycystic kidney disease is linked to aberrant calcium transport and signalling. Furthermore, dysregulation of calcium levels can promote the formation of kidney stones. This Review provides an updated description of the key aspects of calcium handling in the kidney, focusing on the function of various calcium channels and the physiological stimuli that control these channels or are communicated through them. A discussion of the role of calcium as an intracellular second messenger and the pathophysiology of renal calcium dysregulation, as well as a summary of gaps in knowledge and future prospects, are also included.
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Affiliation(s)
- Alexander Staruschenko
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL, USA.
- Hypertension and Kidney Research Center, University of South Florida, Tampa, FL, USA.
- James A. Haley Veterans Hospital, Tampa, FL, USA.
| | - R Todd Alexander
- Department of Paediatrics, University of Alberta, Edmonton, AB, Canada
- Women's and Children's Health Institute, Edmonton, AB, Canada
| | - Michael J Caplan
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA
| | - Daria V Ilatovskaya
- Department of Physiology, Medical College of Georgia, Augusta University, Augusta, GA, USA
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Haykir B, Moser SO, Pastor-Arroyo EM, Schnitzbauer U, Radvanyi Z, Prucker I, Qiu D, Fiedler D, Saiardi A, Jessen HJ, Hernando N, Wagner CA. The Ip6k1 and Ip6k2 Kinases Are Critical for Normal Renal Tubular Function. J Am Soc Nephrol 2024; 35:441-455. [PMID: 38317282 PMCID: PMC11000740 DOI: 10.1681/asn.0000000000000303] [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: 10/05/2023] [Accepted: 12/24/2023] [Indexed: 02/07/2024] Open
Abstract
SIGNIFICANCE STATEMENT Kidneys are gatekeepers of systemic inorganic phosphate balance because they control urinary phosphate excretion. In yeast and plants, inositol hexakisphosphate kinases (IP6Ks) are central to regulate phosphate metabolism, whereas their role in mammalian phosphate homeostasis is mostly unknown. We demonstrate in a renal cell line and in mice that Ip6k1 and Ip6k2 are critical for normal expression and function of the major renal Na + /Pi transporters NaPi-IIa and NaPi-IIc. Moreover, Ip6k1/2-/- mice also show symptoms of more generalized kidney dysfunction. Thus, our results suggest that IP6Ks are essential for phosphate metabolism and proper kidney function in mammals. BACKGROUND Inorganic phosphate is an essential mineral, and its plasma levels are tightly regulated. In mammals, kidneys are critical for maintaining phosphate homeostasis through mechanisms that ultimately regulate the expression of the Na + /Pi cotransporters NaPi-IIa and NaPi-IIc in proximal tubules. Inositol pyrophosphate 5-IP 7 , generated by IP6Ks, is a main regulator of phosphate metabolism in yeast and plants. IP6Ks are conserved in mammals, but their role in phosphate metabolism in vivo remains unexplored. METHODS We used in vitro (opossum kidney cells) and in vivo (renal tubular-specific Ip6k1/2-/- mice) models to analyze the role of IP6K1/2 in phosphate homeostasis in mammals. RESULTS In both systems, Ip6k1 and Ip6k2 are responsible for synthesis of 5-IP 7 . Depletion of Ip6k1/2 in vitro reduced phosphate transport and mRNA expression of Na + /Pi cotransporters, and it blunts phosphate transport adaptation to changes in ambient phosphate. Renal ablation of both kinases in mice also downregulates the expression of NaPi-IIa and NaPi-IIc and lowered the uptake of phosphate into proximal renal brush border membranes. In addition, the absence of Ip6k1 and Ip6k2 reduced the plasma concentration of fibroblast growth factor 23 and increased bone resorption, despite of which homozygous males develop hypophosphatemia. Ip6k1/2-/- mice also show increased diuresis, albuminuria, and hypercalciuria, although the morphology of glomeruli and proximal brush border membrane seemed unaffected. CONCLUSIONS Depletion of renal Ip6k1/2 in mice not only altered phosphate homeostasis but also dysregulated other kidney functions.
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Affiliation(s)
- Betül Haykir
- Switzerland and National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Zürich, Switzerland
| | - Seraina Olivia Moser
- Switzerland and National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Zürich, Switzerland
| | - Eva Maria Pastor-Arroyo
- Switzerland and National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Zürich, Switzerland
| | - Udo Schnitzbauer
- Switzerland and National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Zürich, Switzerland
| | - Zsuzsa Radvanyi
- Switzerland and National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Zürich, Switzerland
| | - Isabel Prucker
- The Center for Integrative Biological Signalling Studies, Institute of Organic Chemistry and CIBSS, University of Freiburg, Freiburg, Germany
| | - Danye Qiu
- The Center for Integrative Biological Signalling Studies, Institute of Organic Chemistry and CIBSS, University of Freiburg, Freiburg, Germany
| | - Dorothea Fiedler
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Adolfo Saiardi
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Henning J. Jessen
- The Center for Integrative Biological Signalling Studies, Institute of Organic Chemistry and CIBSS, University of Freiburg, Freiburg, Germany
| | - Nati Hernando
- Switzerland and National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Zürich, Switzerland
| | - Carsten A. Wagner
- Switzerland and National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Zürich, Switzerland
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Michigami T. Paracrine and endocrine functions of osteocytes. Clin Pediatr Endocrinol 2023; 32:1-10. [PMID: 36761497 PMCID: PMC9887291 DOI: 10.1297/cpe.2022-0053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 08/30/2022] [Indexed: 11/04/2022] Open
Abstract
Osteocytes are dendritic-shaped cells embedded in the bone matrix and are terminally differentiated from osteoblasts. Inaccessibility due to their location has hindered the understanding of the molecular functions of osteocytes. However, scientific advances in the past few decades have revealed that osteocytes play critical roles in bone and mineral metabolism through their paracrine and endocrine functions. Sclerostin produced by osteocytes regulates bone formation and resorption by inhibiting Wnt/β-catenin signaling in osteoblast-lineage cells. Receptor activator of nuclear factor κ B ligand (RANKL) derived from osteocytes is essential for osteoclastogenesis and osteoclast activation during postnatal life. Osteocytes also secrete fibroblast growth factor 23 (FGF23), an endocrine FGF that regulates phosphate metabolism mainly by increasing phosphate excretion and decreasing 1, 25-dihydroxyvitamin D production in the kidneys. The regulation of FGF23 production in osteocytes is complex and multifactorial, involving many local and systemic regulators. Antibodies against sclerostin, RANKL, and FGF23 have emerged as new strategies for the treatment of metabolic bone diseases. Improved undrstanding of the paracrine and endocrine functions of osteocytes will provide insight into future therapeutic options.
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Affiliation(s)
- Toshimi Michigami
- Department of Bone and Mineral Research, Research Institute,
Osaka Women’s and Children’s Hospital, Osaka Prefectural Hospital Organization, Osaka,
Japan
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Radvanyi Z, Daryadel A, Pastor-Arroyo EM, Hernando N, Wagner CA. Does the composition of urinary extracellular vesicles reflect the abundance of renal Na +/phosphate transporters? Pflugers Arch 2022; 474:1201-1212. [PMID: 36074191 PMCID: PMC9560988 DOI: 10.1007/s00424-022-02744-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 08/20/2022] [Accepted: 08/28/2022] [Indexed: 11/28/2022]
Abstract
Studies addressing homeostasis of inorganic phosphate (Pi) are mostly restricted to murine models. Data provided by genetically modified mice suggest that renal Pi reabsorption is primarily mediated by the Na+/Pi cotransporter NaPi-IIa/Slc34a1, whereas the contribution of NaPi-IIc/Slc34a3 in adult animals seems negligible. However, mutations in both cotransporters associate with hypophosphatemic syndromes in humans, suggesting major inter-species heterogeneity. Urinary extracellular vesicles (UEV) have been proposed as an alternative source to analyse the intrinsic expression of renal proteins in vivo. Here, we analyse in rats whether the protein abundance of renal Pi transporters in UEV correlates with their renal content. For that, we compared the abundance of NaPi-IIa and NaPi-IIc in paired samples from kidneys and UEV from rats fed acutely and chronically on diets with low or high Pi. In renal brush border membranes (BBM) NaPi-IIa was detected as two fragments corresponding to the full-length protein and to a proteolytic product, whereas NaPi-IIc migrated as a single full-length band. The expression of NaPi-IIa (both fragments) in BBM adapted to acute as well to chronic changes of dietary Pi, whereas adaptation of NaPi-IIc was only detected in response to chronic administration. Both transporters were detected in UEV as well. UEV reflected the renal adaptation of the NaPi-IIa proteolytic fragment (but not the full-length protein) upon chronic but not acute dietary changes, while also reproducing the chronic regulation of NaPi-IIc. Thus, the composition of UEV reflects only partially changes in the expression of NaPi-IIa and NaPi-IIc at the BBM triggered by dietary Pi.
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Affiliation(s)
- Zsuzsi Radvanyi
- National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Arezoo Daryadel
- National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Eva Maria Pastor-Arroyo
- National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Nati Hernando
- National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Carsten Alexander Wagner
- National Center of Competence in Research NCCR Kidney.CH, Institute of Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
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Abstract
Inorganic phosphate (Pi) in the mammalian body is balanced by its influx and efflux through the intestines, kidneys, bones, and soft tissues, at which several sodium/Pi co-transporters mediate its active transport. Pi homeostasis is achieved through the complex counter-regulatory feedback balance between fibroblast growth factor 23 (FGF23), 1,25-dihydroxyvitamin D (1,25(OH)2D), and parathyroid hormone. FGF23, which is mainly produced by osteocytes in bone, plays a central role in Pi homeostasis and exerts its effects by binding to the FGF receptor (FGFR) and αKlotho in distant target organs. In the kidneys, the main target, FGF23 promotes the excretion of Pi and suppresses the production of 1,25(OH)2D. Deficient and excess FGF23 result in hyperphosphatemia and hypophosphatemia, respectively. FGF23-related hypophosphatemic rickets/osteomalacia include tumor-induced osteomalacia and various genetic diseases, such as X-linked hypophosphatemic rickets. Coverage by the national health insurance system in Japan for the measurement of FGF23 and the approval of burosumab, an FGF23-neutralizing antibody, have had a significant impact on the diagnosis and treatment of FGF23-related hypophosphatemic rickets/osteomalacia. Some of the molecules responsible for genetic hypophosphatemic rickets/osteomalacia are highly expressed in osteocytes and function as local regulators of FGF23 production. A number of systemic factors also regulate FGF23 levels. Although the mechanisms responsible for Pi sensing in mammals have not yet been elucidated in detail, recent studies have suggested the involvement of FGFR1. The further clarification of the mechanisms by which osteocytes detect Pi levels and regulate FGF23 production will lead to the development of better strategies to treat hyperphosphatemic and hypophosphatemic conditions.
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Affiliation(s)
- Toshimi Michigami
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka 594-1101, Japan
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Abstract
Phosphate homeostasis is dependent on the interaction and coordination of four main organ systems: thyroid/parathyroids, gastrointestinal tract, bone and kidneys, and three key hormonal regulators, 1,25-hydroxyvitamin D3, parathyroid hormone and FGF23 with its co- factor klotho. Phosphorus is a critical nutritional element for normal cellular function, but in excess can be toxic to tissues, particularly the vasculature. As phosphate, it also has an important interaction and inter-dependence with calcium and calcium homeostasis sharing some of the same controlling hormones, although this is not covered in our article. We have chosen to provide a current overview of phosphate homeostasis only, focusing on the role of two major organ systems, the gastrointestinal tract and kidneys, and their contribution to the control of phosphate balance. We describe in some detail the mechanisms of intestinal and renal phosphate transport, and compare and contrast their regulation. We also consider a significant example of phosphate imbalance, with phosphate retention, which is chronic kidney disease; why consequent hyperphosphatemia is important, and some of the newer means of managing it.
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Affiliation(s)
- Joanne Marks
- Department of Neuroscience, Physiology & Pharmacology, University College London, London, United Kingdom
| | - Robert J Unwin
- Department of Neuroscience, Physiology & Pharmacology, University College London, London, United Kingdom; Department of Renal Medicine, University College London, London, United Kingdom.
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Fu C, Pei Q, Liang W, Yang B, Li W, Liu J, Tan H, Guo C, Zhang H, Yang G. Population Pharmacokinetic Modelling for Nifedipine to Evaluate the Effect of Parathyroid Hormone on CYP3A in Patients with Chronic Kidney Disease. Drug Des Devel Ther 2022; 16:2261-2274. [PMID: 35860523 PMCID: PMC9289454 DOI: 10.2147/dddt.s362607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Accepted: 06/30/2022] [Indexed: 11/30/2022] Open
Abstract
Purpose Parathyroid hormone (PTH) can induce the downregulation of CYP3A in chronic kidney disease (CKD). Nevertheless, the effect of PTH on CYP3A-mediated clearance pathways from a clinical perspective remains unclear. Methods This study employed population pharmacokinetic (PopPK) modeling to delineate potential changes in CYP3A activity in patients with CKD. Pharmacokinetic data for nifedipine, a typical CYP3A substrate, as well as covariate information, were prospectively collected from 157 patients with a total of 612 concentrations. PopPK data analysis was performed using a nonlinear mixed-effects model. Results The pharmacokinetics of nifedipine were optimally described according to a one-compartment model with zero-order absorption and first-order elimination. The estimated population parameters (and interindividual variability) were apparent clearance (CL/F) 49.61 L/h (58.33%) and apparent volume of distribution (V/F) 2300.26 L (45.62%), and the PTH level negatively correlated with CL/F. In comparison with the reference level, it was observed that the dosage of nifedipine should be reduced with the maximum boundary value of PTH, after a Monte Carlo simulation. Conclusion This study provides insight into the effects of PTH on CYP3A-mediated clearance pathways. Moreover, PTH could be used as a guide for the appropriate administration of CYP3A eliminated drugs in patients with CKD.
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Affiliation(s)
- Chengxiao Fu
- Center for Clinical Pharmacology, The Third Xiangya Hospital, Central South University, Changsha, People’s Republic of China
- The First Affiliated Hospital, Department of Pharmacy, Hengyang Medical School, University of South China, Hengyang, People’s Republic of China
| | - Qi Pei
- Department of Pharmacy, The Third Xiangya Hospital, Central South University, Changsha, People’s Republic of China
| | - Wu Liang
- Research Center of Drug Clinical Evaluation of Central South University, Changsha, People’s Republic of China
| | - Bo Yang
- The First Affiliated Hospital, Department of Pharmacy, Hengyang Medical School, University of South China, Hengyang, People’s Republic of China
| | - Wei Li
- Department of Nephrology, The Third Xiangya Hospital, Central South University, Changsha, People’s Republic of China
| | - Jun Liu
- Department of Nephrology, The Third Xiangya Hospital, Central South University, Changsha, People’s Republic of China
| | - Hongyi Tan
- Center for Clinical Pharmacology, The Third Xiangya Hospital, Central South University, Changsha, People’s Republic of China
- Research Center of Drug Clinical Evaluation of Central South University, Changsha, People’s Republic of China
| | - Chengxian Guo
- Center for Clinical Pharmacology, The Third Xiangya Hospital, Central South University, Changsha, People’s Republic of China
- Research Center of Drug Clinical Evaluation of Central South University, Changsha, People’s Republic of China
| | - Hao Zhang
- Department of Nephrology, The Third Xiangya Hospital, Central South University, Changsha, People’s Republic of China
| | - Guoping Yang
- Center for Clinical Pharmacology, The Third Xiangya Hospital, Central South University, Changsha, People’s Republic of China
- Research Center of Drug Clinical Evaluation of Central South University, Changsha, People’s Republic of China
- Correspondence: Guoping Yang; Hao Zhang, Email ;
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Pathogenesis of FGF23-Related Hypophosphatemic Diseases Including X-linked Hypophosphatemia. ENDOCRINES 2022. [DOI: 10.3390/endocrines3020025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Since phosphate is indispensable for skeletal mineralization, chronic hypophosphatemia causes rickets and osteomalacia. Fibroblast growth factor 23 (FGF23), which is mainly produced by osteocytes in bone, functions as the central regulator of phosphate metabolism by increasing the renal excretion of phosphate and suppressing the production of 1,25-dihydroxyvitamin D. The excessive action of FGF23 results in hypophosphatemic diseases, which include a number of genetic disorders such as X-linked hypophosphatemic rickets (XLH) and tumor-induced osteomalacia (TIO). Phosphate-regulating gene homologous to endopeptidase on the X chromosome (PHEX), dentin matrix protein 1 (DMP1), ectonucleotide pyrophosphatase phosphodiesterase-1, and family with sequence similarity 20c, the inactivating variants of which are responsible for FGF23-related hereditary rickets/osteomalacia, are highly expressed in osteocytes, similar to FGF23, suggesting that they are local negative regulators of FGF23. Autosomal dominant hypophosphatemic rickets (ADHR) is caused by cleavage-resistant variants of FGF23, and iron deficiency increases serum levels of FGF23 and the manifestation of symptoms in ADHR. Enhanced FGF receptor (FGFR) signaling in osteocytes is suggested to be involved in the overproduction of FGF23 in XLH and autosomal recessive hypophosphatemic rickets type 1, which are caused by the inactivation of PHEX and DMP1, respectively. TIO is caused by the overproduction of FGF23 by phosphaturic tumors, which are often positive for FGFR. FGF23-related hypophosphatemia may also be associated with McCune-Albright syndrome, linear sebaceous nevus syndrome, and the intravenous administration of iron. This review summarizes current knowledge on the pathogenesis of FGF23-related hypophosphatemic diseases.
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Koiwa F, Yazawa R, Fukagawa M, Honda D, Akizawa T. First-in-Human Phase I Study of the Novel Injectable Calcimimetic Agent Upacicalcet in Healthy Adult Japanese Participants. Drugs R D 2022; 22:131-140. [PMID: 35338469 PMCID: PMC9167405 DOI: 10.1007/s40268-022-00385-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/07/2022] [Indexed: 11/29/2022] Open
Abstract
Background and Objective Upacicalcet sodium hydrate is a novel small-molecule calcimimetic and has potential as a therapeutic agent for secondary hyperparathyroidism. We assessed the pharmacokinetics, pharmacodynamics, safety, and tolerability of a single intravenous dose of upacicalcet in Japanese healthy adults. Method This was a single-center, double-blinded, randomized, placebo-controlled, dose-escalation study. For each cohort, eight subjects were randomly assigned at a ratio of 3:1 to receive a single injection of placebo or upacicalcet 0.01, 0.1, 1.0, or 2.5 mg. Result The plasma concentration of upacicalcet increased in a dose-dependent manner. Upacicalcet rapidly disappeared from plasma after administration. The half-life of upacicalcet was approximately 1–2 h. The major excretion route of upacicalcet was via urine. Serum intact parathyroid hormone decreased in accordance with the upacicalcet dose, from the lowest dose of 0.01 mg. Gastrointestinal disorders occurred in one patient in the 1.0 mg group and in five patients in the 2.5 mg group. All adverse events were nonserious, and no symptomatic hypocalcemia occurred. Conclusion This study showed that upacicalcet acted as a calcimimetic and was excreted in the urine unchanged with little metabolism. Moreover, upacicalcet is a small molecule and has a small volume of distribution. In addition, less than 50% of upacicalcet binds to human plasma proteins. These findings suggest that upacicalcet administered to patients undergoing hemodialysis might be expected to have a long excretion period and sustained pharmacological effect.
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Affiliation(s)
- Fumihiko Koiwa
- Division of Nephrology, Department of Internal Medicine, Showa University Fujigaoka Hospital, Yokohama, Japan
| | - Rie Yazawa
- Sumida Hospital, Souseikai, Tokyo, Japan
| | - Masafumi Fukagawa
- Division of Nephrology, Endocrinology and Metabolism, Tokai University School of Medicine, Isehara, Japan
| | - Daisuke Honda
- Project Management Department, Sanwa Kagaku Kenkyusho Co., Ltd, Nagoya, Japan.
| | - Tadao Akizawa
- Division of Nephrology, Department of Medicine, Showa University School of Medicine, Tokyo, Japan
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Sasaki S, Shiozaki Y, Hanazaki A, Koike M, Tanifuji K, Uga M, Kawahara K, Kaneko I, Kawamoto Y, Wiriyasermkul P, Hasegawa T, Amizuka N, Miyamoto KI, Nagamori S, Kanai Y, Segawa H. Tmem174, a regulator of phosphate transporter prevents hyperphosphatemia. Sci Rep 2022; 12:6353. [PMID: 35428804 PMCID: PMC9012787 DOI: 10.1038/s41598-022-10409-3] [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: 12/01/2021] [Accepted: 04/05/2022] [Indexed: 11/23/2022] Open
Abstract
Renal type II sodium-dependent inorganic phosphate (Pi) transporters NaPi2a and NaPi2c cooperate with other organs to strictly regulate the plasma Pi concentration. A high Pi load induces expression and secretion of the phosphaturic hormones parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) that enhance urinary Pi excretion and prevent the onset of hyperphosphatemia. How FGF23 secretion from bone is increased by a high Pi load and the setpoint of the plasma Pi concentration, however, are unclear. Here, we investigated the role of Transmembrane protein 174 (Tmem174) and observed evidence for gene co-expression networks in NaPi2a and NaPi2c function. Tmem174 is localized in the renal proximal tubules and interacts with NaPi2a, but not NaPi2c. In Tmem174-knockout (KO) mice, the serum FGF23 concentration was markedly increased but increased Pi excretion and hypophosphatemia were not observed. In addition, Tmem174-KO mice exhibit reduced NaPi2a responsiveness to FGF23 and PTH administration. Furthermore, a dietary Pi load causes marked hyperphosphatemia and abnormal NaPi2a regulation in Tmem174-KO mice. Thus, Tmem174 is thought to be associated with FGF23 induction in bones and the regulation of NaPi2a to prevent an increase in the plasma Pi concentration due to a high Pi load and kidney injury.
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Affiliation(s)
- Sumire Sasaki
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Yuji Shiozaki
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Ai Hanazaki
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Megumi Koike
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Kazuya Tanifuji
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Minori Uga
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Kota Kawahara
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Ichiro Kaneko
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Yasuharu Kawamoto
- Department of Bio-System Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Pattama Wiriyasermkul
- Department of Laboratory Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | - Tomoka Hasegawa
- Developmental Biology of Hard Tissue, Faculty of Dental Medicine, Hokkaido University, Sapporo, Japan
| | - Norio Amizuka
- Developmental Biology of Hard Tissue, Faculty of Dental Medicine, Hokkaido University, Sapporo, Japan
| | - Ken-Ichi Miyamoto
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan.,Graduate School of Agriculture, Ryukoku University, Ohtsu, Japan
| | - Shushi Nagamori
- Department of Laboratory Medicine, The Jikei University School of Medicine, Tokyo, Japan.
| | - Yoshikatsu Kanai
- Department of Bio-System Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan.
| | - Hiroko Segawa
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan.
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Küng CJ, Haykir B, Schnitzbauer U, Egli-Spichtig D, Hernando N, Wagner CA. Fibroblast growth factor 23 leads to endolysosomal routing of the renal phosphate cotransporters NaPi-IIa and NaPi-IIc in vivo. Am J Physiol Renal Physiol 2021; 321:F785-F798. [PMID: 34719948 DOI: 10.1152/ajprenal.00250.2021] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Na+-dependent phosphate cotransporters NaPi-IIa and NaPi-IIc, located at the brush-border membrane of renal proximal tubules, are regulated by numerous factors, including fibroblast growth factor 23 (FGF23). FGF23 downregulates NaPi-IIa and NaPi-IIc abundance after activating a signaling pathway involving phosphorylation of ERK1/2 (phospho-ERK1/2). FGF23 also downregulates expression of renal 1-α-hydroxylase (Cyp27b1) and upregulates 24-hydroxylase (Cyp24a1), thus reducing plasma calcitriol levels. Here, we examined the time course of FGF23-induced internalization of NaPi-IIa and NaPi-IIc and their intracellular pathway toward degradation in vivo. Mice were injected intraperitoneally with recombinant human (rh)FGF23 in the absence (biochemical analysis) or presence (immunohistochemistry) of leupeptin, an inhibitor of lysosomal proteases. Phosphorylation of ERK1/2 was enhanced 60 min after rhFGF23 administration, and increased phosphorylation was still detected 480 min after injection. Colocalization of phospho-ERK1/2 with NaPi-IIa was seen at 60 and 120 min and partly at 480 min. The abundance of both cotransporters was reduced 240 min after rhFGF23 administration, with a further reduction at 480 min. NaPi-IIa and NaPi-IIc were found to colocalize with clathrin and early endosomal antigen 1 as early as 120 min after rhFGF23 injection. Both cotransporters partially colocalized with cathepsin B and lysosomal-associated membrane protein-1, markers of lysosomes, 120 min after rhFGF23 injection. Thus, NaPi-IIa and NaPi-IIc are internalized within 2 h upon rhFGF23 injection. Both cotransporters share the pathway of clathrin-mediated endocytosis that leads first to early endosomes, finally resulting in trafficking toward the lysosome as early as 120 min after rhFGF23 administration.NEW & NOTEWORTHY The hormone fibroblast growth factor 23 (FGF23) controls phosphate homeostasis by regulating renal phosphate excretion. FGF23 acts on several phosphate transporters in the kidney. Here, we define the time course of this action and demonstrate how phosphate transporters NaPi-IIa and NaPi-IIc are internalized.
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Affiliation(s)
- Catharina J Küng
- Institute of Physiology, University of Zurich and National Center of Competence in Research Kidney.CH, Zurich, Switzerland
| | - Betül Haykir
- Institute of Physiology, University of Zurich and National Center of Competence in Research Kidney.CH, Zurich, Switzerland
| | - Udo Schnitzbauer
- Institute of Physiology, University of Zurich and National Center of Competence in Research Kidney.CH, Zurich, Switzerland
| | - Daniela Egli-Spichtig
- Institute of Physiology, University of Zurich and National Center of Competence in Research Kidney.CH, Zurich, Switzerland
| | - Nati Hernando
- Institute of Physiology, University of Zurich and National Center of Competence in Research Kidney.CH, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich and National Center of Competence in Research Kidney.CH, Zurich, Switzerland
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12
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Adhikari S, Mamlouk O, Rondon-Berrios H, Workeneh BT. Hypophosphatemia in cancer patients. Clin Kidney J 2021; 14:2304-2315. [PMID: 34754427 PMCID: PMC8572986 DOI: 10.1093/ckj/sfab078] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Indexed: 12/19/2022] Open
Abstract
Dysregulation of phosphorus homeostasis resulting in hypophosphatemia is common in cancer patients and can result in serious complications and impact outcomes. Several factors, including critical illness, nutritional status, cancer type and therapy, influence the development of hypophosphatemia. Hypophosphatemia can develop as a result of phosphaturic mesenchymal tumors or as a paraneoplastic phenomenon. The clinical presentation for hypophosphatemia varies depending on the duration and severity of the hypophosphatemia and affects several organ systems. Among other serious effects, hypophosphatemia can impair tissue oxygenation and can cause hemolysis, leukocyte and platelet dysfunction, encephalopathy, seizures, arrhythmias, cardiomyopathy, rhabdomyolysis and coma. Multiple studies have demonstrated that hypophosphatemia is an adverse prognostic marker in inpatients with increased in-hospital stay, mortality and postoperative complications. The phosphate level is homeostatically regulated and maintained in a narrow range by three main hormones: parathyroid hormone, fibroblast growth factor 23 and 1,25-dihydroxyvitaminD3. Together, these hormones regulate how the intestine, kidneys and bones traffic phosphorus. Several hematological malignancies and cancer therapies are associated with proximal tubular dysfunction (Fanconi syndrome), resulting in phosphaturia. Caution should be taken with parenteral administration of phosphate salts, because secondary complications can develop, principally due to hypocalcemia. The general approach to hypophosphatemia should target the underlying cause. Early recognition and prevention are essential and the approach to hypophosphatemia in the cancer patient, because of the nuances and complexity, should be multidisciplinary.
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Affiliation(s)
- Shreedhar Adhikari
- Division of Renal-Electrolyte, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Omar Mamlouk
- Section of Nephrology, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Helbert Rondon-Berrios
- Division of Renal-Electrolyte, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Biruh T Workeneh
- Section of Nephrology, University of Texas MD Anderson Cancer Center, Houston, TX, USA
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13
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Bird RP, Eskin NAM. The emerging role of phosphorus in human health. ADVANCES IN FOOD AND NUTRITION RESEARCH 2021; 96:27-88. [PMID: 34112356 DOI: 10.1016/bs.afnr.2021.02.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Phosphorus, an essential nutrient, performs vital functions in skeletal and non-skeletal tissues and is pivotal for energy production. The last two decades of research on the physiological importance of phosphorus have provided several novel insights about its dynamic nature as a nutrient performing functions as a phosphate ion. Phosphorous also acts as a signaling molecule and induces complex physiological responses. It is recognized that phosphorus homeostasis is critical for health. The intake of phosphorus by the general population world-wide is almost double the amount required to maintain health. This increase is attributed to the incorporation of phosphate containing food additives in processed foods purchased by consumers. Research findings assessed the impact of excessive phosphorus intake on cells' and organs' responses, and highlighted the potential pathogenic consequences. Research also identified a new class of bioactive phosphates composed of polymers of phosphate molecules varying in chain length. These polymers are involved in metabolic responses including hemostasis, brain and bone health, via complex mechanism(s) with positive or negative health effects, depending on their chain length. It is amazing, that phosphorus, a simple element, is capable of exerting multiple and powerful effects. The role of phosphorus and its polymers in the renal and cardiovascular system as well as on brain health appear to be important and promising future research directions.
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Affiliation(s)
- Ranjana P Bird
- School of Health Sciences, University of Northern British Columbia, Prince George, BC, Canada.
| | - N A Michael Eskin
- Department of Food and Human Nutritional Sciences, Faculty of Agricultural and Food Sciences, University of Manitoba, Winnipeg, MB, Canada
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14
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Kulesza T, Piwkowska A. The impact of type III sodium-dependent phosphate transporters (Pit 1 and Pit 2) on podocyte and kidney function. J Cell Physiol 2021; 236:7176-7185. [PMID: 33738792 DOI: 10.1002/jcp.30368] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 02/26/2021] [Accepted: 03/04/2021] [Indexed: 01/07/2023]
Abstract
The sodium-dependent phosphate transporters Pit 1 and Pit 2 belong to the solute carrier 20 (SLC20) family of membrane proteins. They are ubiquitously distributed in the human body. Their crucial function is the intracellular transport of inorganic phosphate (Pi) in the form of H2 PO4 - . They are one of the main elements in maintaining physiological phosphate homeostasis. Recent data have emerged that indicate novel roles of Pit 1 and Pit 2 proteins besides the well-known function of Pi transporters. These membrane proteins are believed to be precise phosphate sensors that mediate Pi-dependent intracellular signaling. They are also involved in insulin signaling and influence cellular insulin sensitivity. In diseases that are associated with hyperphosphatemia, such as diabetes and chronic kidney disease (CKD), disturbances in the function of Pit 1 and Pit 2 are observed. Phosphate transporters from the SLC20 family participate in the calcification of soft tissues, mainly blood vessels, during the course of CKD. The glomerulus and podocytes therein can also be a target of pathological calcification that damages these structures. A few studies have demonstrated the development of Pi-dependent podocyte injury that is mediated by Pit 1 and Pit 2. This paper discusses the role of Pit 1 and Pit 2 proteins in podocyte function, mainly in the context of the development of pathological calcification that disrupts permeability of the renal filtration barrier. We also describe the mechanisms that may contribute to podocyte damage by Pit 1 and Pit 2.
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Affiliation(s)
- Tomasz Kulesza
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Gdansk, Poland
| | - Agnieszka Piwkowska
- Laboratory of Molecular and Cellular Nephrology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Gdansk, Poland
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15
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Yoshii I, Nishiyama S. The impact of shrunken pore syndrome in patient with rheumatic diseases on bone mineral metabolism. Scandinavian Journal of Clinical and Laboratory Investigation 2020; 81:72-81. [DOI: 10.1080/00365513.2020.1858492] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Ichiro Yoshii
- Department of Rheumatology and Musculoskeletal Medicine, Yoshii Hospital, Shimanto-City, Kochi Prefecture, Japan
| | - Susumu Nishiyama
- Department of Rheumatic Disease Center, Kurashiki Medical Center, Okayama, Prefecture, Japan
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16
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Physical Activity-Dependent Regulation of Parathyroid Hormone and Calcium-Phosphorous Metabolism. Int J Mol Sci 2020; 21:ijms21155388. [PMID: 32751307 PMCID: PMC7432834 DOI: 10.3390/ijms21155388] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 07/09/2020] [Accepted: 07/23/2020] [Indexed: 12/14/2022] Open
Abstract
Exercise perturbs homeostasis, alters the levels of circulating mediators and hormones, and increases the demand by skeletal muscles and other vital organs for energy substrates. Exercise also affects bone and mineral metabolism, particularly calcium and phosphate, both of which are essential for muscle contraction, neuromuscular signaling, biosynthesis of adenosine triphosphate (ATP), and other energy substrates. Parathyroid hormone (PTH) is involved in the regulation of calcium and phosphate homeostasis. Understanding the effects of exercise on PTH secretion is fundamental for appreciating how the body adapts to exercise. Altered PTH metabolism underlies hyperparathyroidism and hypoparathyroidism, the complications of which affect the organs involved in calcium and phosphorous metabolism (bone and kidney) and other body systems as well. Exercise affects PTH expression and secretion by altering the circulating levels of calcium and phosphate. In turn, PTH responds directly to exercise and exercise-induced myokines. Here, we review the main concepts of the regulation of PTH expression and secretion under physiological conditions, in acute and chronic exercise, and in relation to PTH-related disorders.
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17
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Abstract
Parathyroid hormone is an essential regulator of extracellular calcium and phosphate. PTH enhances calcium reabsorption while inhibiting phosphate reabsorption in the kidneys, increases the synthesis of 1,25-dihydroxyvitamin D, which then increases gastrointestinal absorption of calcium, and increases bone resorption to increase calcium and phosphate. Parathyroid disease can be an isolated endocrine disorder or part of a complex syndrome. Genetic mutations can account for diseases of parathyroid gland formulation, dysregulation of parathyroid hormone synthesis or secretion, and destruction of the parathyroid glands. Over the years, a number of different options are available for the treatment of different types of parathyroid disease. Therapeutic options include surgical removal of hypersecreting parathyroid tissue, administration of parathyroid hormone, vitamin D, activated vitamin D, calcium, phosphate binders, calcium-sensing receptor, and vitamin D receptor activators to name a few. The accurate assessment of parathyroid hormone also provides essential biochemical information to properly diagnose parathyroid disease. Currently available immunoassays may overestimate or underestimate bioactive parathyroid hormone because of interferences from truncated parathyroid hormone fragments, phosphorylation of parathyroid hormone, and oxidation of amino acids of parathyroid hormone.
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Affiliation(s)
- Edward Ki Yun Leung
- Department of Pathology and Laboratory Medicine, Children's Hospital Los Angeles, Los Angeles, CA, United States; Department of Pathology, Keck School of Medicine of University of Southern California, Los Angeles, CA, United States.
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18
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Abstract
Phosphate is an essential nutrient for life and is a critical component of bone formation, a major signaling molecule, and structural component of cell walls. Phosphate is also a component of high-energy compounds (i.e., AMP, ADP, and ATP) and essential for nucleic acid helical structure (i.e., RNA and DNA). Phosphate plays a central role in the process of mineralization, normal serum levels being associated with appropriate bone mineralization, while high and low serum levels are associated with soft tissue calcification. The serum concentration of phosphate and the total body content of phosphate are highly regulated, a process that is accomplished by the coordinated effort of two families of sodium-dependent transporter proteins. The three isoforms of the SLC34 family (SLC34A1-A3) show very restricted tissue expression and regulate intestinal absorption and renal excretion of phosphate. SLC34A2 also regulates the phosphate concentration in multiple lumen fluids including milk, saliva, pancreatic fluid, and surfactant. Both isoforms of the SLC20 family exhibit ubiquitous expression (with some variation as to which one or both are expressed), are regulated by ambient phosphate, and likely serve the phosphate needs of the individual cell. These proteins exhibit similarities to phosphate transporters in nonmammalian organisms. The proteins are nonredundant as mutations in each yield unique clinical presentations. Further research is essential to understand the function, regulation, and coordination of the various phosphate transporters, both the ones described in this review and the phosphate transporters involved in intracellular transport.
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Affiliation(s)
- Nati Hernando
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
| | - Kenneth Gagnon
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
| | - Eleanor Lederer
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
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19
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Motta SE, Imenez Silva PH, Daryadel A, Haykir B, Pastor-Arroyo EM, Bettoni C, Hernando N, Wagner CA. Expression of NaPi-IIb in rodent and human kidney and upregulation in a model of chronic kidney disease. Pflugers Arch 2020; 472:449-460. [PMID: 32219532 DOI: 10.1007/s00424-020-02370-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 02/29/2020] [Accepted: 03/20/2020] [Indexed: 01/07/2023]
Abstract
Na+-coupled phosphate cotransporters from the SLC34 and SLC20 families of solute carriers mediate transepithelial transport of inorganic phosphate (Pi). NaPi-IIa/Slc34a1, NaPi-IIc/Slc34a3, and Pit-2/Slc20a2 are all expressed at the apical membrane of renal proximal tubules and therefore contribute to renal Pi reabsorption. Unlike NaPi-IIa and NaPi-IIc, which are rather kidney-specific, NaPi-IIb/Slc34a2 is expressed in several epithelial tissues, including the intestine, lung, testis, and mammary glands. Recently, the expression of NaPi-IIb was also reported in kidneys from rats fed on high Pi. Here, we systematically quantified the mRNA expression of SLC34 and SLC20 cotransporters in kidneys from mice, rats, and humans. In all three species, NaPi-IIa mRNA was by far the most abundant renal transcript. Low and comparable mRNA levels of the other four transporters, including NaPi-IIb, were detected in kidneys from rodents and humans. In mice, the renal expression of NaPi-IIa transcripts was restricted to the cortex, whereas NaPi-IIb mRNA was observed in medullary segments. Consistently, NaPi-IIb protein colocalized with uromodulin at the luminal membrane of thick ascending limbs of the loop of Henle segments. The abundance of NaPi-IIb transcripts in kidneys from mice was neither affected by dietary Pi, the absence of renal NaPi-IIc, nor the depletion of intestinal NaPi-IIb. In contrast, it was highly upregulated in a model of oxalate-induced kidney disease where all other SLC34 phosphate transporters were downregulated. Thus, NaPi-IIb may contribute to renal phosphate reabsorption, and its upregulation in kidney disease might promote hyperphosphatemia.
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Affiliation(s)
- Sarah E Motta
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Pedro Henrique Imenez Silva
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Arezoo Daryadel
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Betül Haykir
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Eva Maria Pastor-Arroyo
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Carla Bettoni
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Nati Hernando
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
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20
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Abstract
Over the past 25 years, successive cloning of SLC34A1, SLC34A2 and SLC34A3, which encode the sodium-dependent inorganic phosphate (Pi) cotransport proteins 2a-2c, has facilitated the identification of molecular mechanisms that underlie the regulation of renal and intestinal Pi transport. Pi and various hormones, including parathyroid hormone and phosphatonins, such as fibroblast growth factor 23, regulate the activity of these Pi transporters through transcriptional, translational and post-translational mechanisms involving interactions with PDZ domain-containing proteins, lipid microdomains and acute trafficking of the transporters via endocytosis and exocytosis. In humans and rodents, mutations in any of the three transporters lead to dysregulation of epithelial Pi transport with effects on serum Pi levels and can cause cardiovascular and musculoskeletal damage, illustrating the importance of these transporters in the maintenance of local and systemic Pi homeostasis. Functional and structural studies have provided insights into the mechanism by which these proteins transport Pi, whereas in vivo and ex vivo cell culture studies have identified several small molecules that can modify their transport function. These small molecules represent potential new drugs to help maintain Pi homeostasis in patients with chronic kidney disease - a condition that is associated with hyperphosphataemia and severe cardiovascular and skeletal consequences.
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21
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Bär L, Stournaras C, Lang F, Föller M. Regulation of fibroblast growth factor 23 (FGF23) in health and disease. FEBS Lett 2019; 593:1879-1900. [PMID: 31199502 DOI: 10.1002/1873-3468.13494] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 03/26/2019] [Accepted: 03/27/2019] [Indexed: 12/19/2022]
Abstract
Fibroblast growth factor 23 (FGF23) is mainly produced in the bone and, upon secretion, forms a complex with a FGF receptor and coreceptor αKlotho. FGF23 can exert several endocrine functions, such as inhibiting renal phosphate reabsorption and 1,25-dihydroxyvitamin D3 production. Moreover, it has paracrine activities on several cell types, including neutrophils and hepatocytes. Klotho and Fgf23 deficiencies result in pathologies otherwise encountered in age-associated diseases, mainly as a result of hyperphosphataemia-dependent calcification. FGF23 levels are also perturbed in the plasma of patients with several disorders, including kidney or cardiovascular diseases. Here, we review mechanisms controlling FGF23 production and discuss how FGF23 regulation is perturbed in disease.
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Affiliation(s)
- Ludmilla Bär
- Institute of Agricultural and Nutritional Sciences, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Christos Stournaras
- Institute of Biochemistry, University of Crete Medical School, Heraklion, Greece
| | - Florian Lang
- Institute of Physiology, University of Tübingen, Germany
| | - Michael Föller
- Institute of Physiology, University of Hohenheim, Stuttgart, Germany
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22
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Mizutani N, Okochi Y, Okamura Y. Distinct functional properties of two electrogenic isoforms of the SLC34 Na-Pi cotransporter. Physiol Rep 2019; 7:e14156. [PMID: 31342668 PMCID: PMC6656865 DOI: 10.14814/phy2.14156] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Revised: 05/02/2019] [Accepted: 05/03/2019] [Indexed: 01/05/2023] Open
Abstract
Inorganic phosphate (Pi ) is crucial for proper cellular function in all organisms. In mammals, type II Na-Pi cotransporters encoded by members of the Slc34 gene family play major roles in the maintenance of Pi homeostasis. However, the molecular mechanisms regulating Na-Pi cotransporter activity within the plasma membrane are largely unknown. In the present study, we used two approaches to examine the effect of changing plasma membrane phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2 ) levels on the activities of two electrogenic Na-Pi cotransporters, NaPi-IIa and NaPi-IIb. To deplete plasma membrane PI(4,5)P2 in Xenopus oocytes, we utilized Ciona intestinalis voltage-sensing phosphatase (Ci-VSP), which dephosphorylates PI(4,5)P2 to phosphatidylinositol 4-phosphate (PI(4)P). Upon activation of Ci-VSP, NaPi-IIb currents were significantly decreased, whereas NaPi-IIa currents were unaffected. We also used the rapamycin-inducible Pseudojanin (PJ) system to deplete both PI(4,5)P2 and PI(4)P from the plasma membrane of cultured Neuro 2a cells. Depletion of PI(4,5)P2 and PI(4)P using PJ significantly reduced NaPi-IIb activity, but NaPi-IIa activity was unaffected, which excluded the possibility that NaPi-IIa is equally sensitive to PI(4,5)P2 and PI(4)P. These results indicate that NaPi-IIb activity is regulated by PI(4,5)P2 , whereas NaPi-IIa is not sensitive to either PI(4,5)P2 or PI(4)P. In addition, patch clamp recording of NaPi-IIa and NaPi-IIb currents in cultured mammalian cells enabled kinetic analysis with higher temporal resolution, revealing their distinct kinetic properties.
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Affiliation(s)
- Natsuki Mizutani
- Laboratory of Integrative PhysiologyDepartment of PhysiologyGraduate School of MedicineOsaka UniversitySuitaOsakaJapan
| | - Yoshifumi Okochi
- Laboratory of Integrative PhysiologyDepartment of PhysiologyGraduate School of MedicineOsaka UniversitySuitaOsakaJapan
| | - Yasushi Okamura
- Laboratory of Integrative PhysiologyDepartment of PhysiologyGraduate School of MedicineOsaka UniversitySuitaOsakaJapan
- Graduate School of Frontier BiosciencesOsaka UniversitySuitaOsakaJapan
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23
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Role of the putative PKC phosphorylation sites of the type IIc sodium-dependent phosphate transporter in parathyroid hormone regulation. Clin Exp Nephrol 2019; 23:898-907. [DOI: 10.1007/s10157-019-01725-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Accepted: 03/01/2019] [Indexed: 11/26/2022]
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24
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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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25
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Visualizing the regulation of SLC34 proteins at the apical membrane. Pflugers Arch 2019; 471:533-542. [PMID: 30613865 DOI: 10.1007/s00424-018-02249-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 12/19/2018] [Accepted: 12/20/2018] [Indexed: 10/27/2022]
Abstract
The cloning of the renal NaPi-2a (SLC34A1) and NaPi-2c (SLC34A3) phosphate transporters has made it possible to characterize the molecular and biophysical regulation of renal proximal tubular reabsorption of inorganic phosphate (Pi). Dietary factors, such as Pi and K, and several hormones and phosphatonins, including parathyroid hormone (PTH), fibroblast growth factor 23 (FGF23), and glucocorticoids, regulate the transporters through various transcriptional, translational, and post-translational mechanisms that involve acute trafficking via endocytosis or exocytosis, interactions with PDZ domain proteins, lipid microdomains, and diffusion and clustering in the apical brush border membrane. The visualization of these trafficking events by means of novel microscopy techniques that includes fluorescence lifetime imaging microscopy (FLIM), Förster resonance energy transfer (FRET), fluctuation correlation spectroscopy (FCS), and modulation tracking (MT), is the primary focus of this review.
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26
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Abstract
Phosphate is essential for skeletal mineralization, and its chronic deficiency leads to rickets and osteomalacia. Skeletal mineralization starts in matrix vesicles (MVs) derived from the plasma membrane of osteoblasts and chondrocytes. MVs contain high activity of tissue non-specific alkaline phosphatase (TNSALP), which hydrolyzes phosphoric esters such as pyrophosphates (PPi) to produce inorganic orthophosphates (Pi). Extracellular Pi in the skeleton is taken up by MVs through type III sodium/phosphate (Na+/Pi) cotransporters and forms hydroxyapatite. In addition to its roles in MV-mediated skeletal mineralization, accumulating evidence has revealed that extracellular Pi evokes signal transduction and regulates cellular function. Pi induces apoptosis of hypertrophic chondrocytes, which is a critical step for endochondral ossification. Extracellular Pi also regulates the expression of various genes including those related to proliferation, differentiation, and mineralization. In vitro cell studies have demonstrated that an elevation in extracellular Pi level leads to the activation of fibroblast growth factor receptor (FGFR), Raf/MEK (mitogen-activated protein kinase/ERK kinase)/ERK (extracellular signal-regulated kinase) pathway, where the type III Na+/Pi cotransporter PiT-1 may be involved. Responsiveness of skeletal cells to extracellular Pi suggests their ability to sense and adapt to an alteration in Pi availability in their environment. Involvement of FGFR in the Pi-evoked signal transduction is interesting because enhanced FGFR signaling in osteoblasts/osteocytes might be responsible for the overproduction of FGF23, a key molecule in phosphate homeostasis, in a mouse model for human X-linked hypophosphatemic rickets (XLH). Impaired Pi sensing may be a pathogenesis of XLH, which needs to be clarified in future.
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Affiliation(s)
- Toshimi Michigami
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Izumi, Japan
- *Correspondence: Toshimi Michigami
| | - Keiichi Ozono
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
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27
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Abstract
Parathyroid hormone (PTH) is the major secretory product of the parathyroid glands, and in hypocalcemic conditions, can enhance renal calcium reabsorption, increase active vitamin D production to increase intestinal calcium absorption, and mobilize calcium from bone by increasing turnover, mainly but not exclusively in cortical bone. PTH has therefore found clinical use as replacement therapy in hypoparathyroidism. PTH also may have a physiologic role in augmenting bone formation, particularly in trabecular and to some extent in cortical bone. This action has been applied to the clinic to provide anabolic therapy for osteoporosis.
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Affiliation(s)
- David Goltzman
- Department of Medicine and Research Institute of the McGill University Health Centre, 1001 Decarie Boulevard, Montreal, Quebec H4A 3J1, Canada; Departments of Medicine and of Physiology, McGill University, 845 Sherbrooke St West, Montreal, Quebec H3A 0B9, Canada.
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Michigami T, Kawai M, Yamazaki M, Ozono K. Phosphate as a Signaling Molecule and Its Sensing Mechanism. Physiol Rev 2018; 98:2317-2348. [DOI: 10.1152/physrev.00022.2017] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
In mammals, phosphate balance is maintained by influx and efflux via the intestines, kidneys, bone, and soft tissue, which involves multiple sodium/phosphate (Na+/Pi) cotransporters, as well as regulation by several hormones. Alterations in the levels of extracellular phosphate exert effects on both skeletal and extra-skeletal tissues, and accumulating evidence has suggested that phosphate itself evokes signal transduction to regulate gene expression and cell behavior. Several in vitro studies have demonstrated that an elevation in extracellular Piactivates fibroblast growth factor receptor, Raf/MEK (mitogen-activated protein kinase/ERK kinase)/ERK (extracellular signal-regulated kinase) pathway and Akt pathway, which might involve the type III Na+/Picotransporter PiT-1. Excessive phosphate loading can lead to various harmful effects by accelerating ectopic calcification, enhancing oxidative stress, and dysregulating signal transduction. The responsiveness of mammalian cells to altered extracellular phosphate levels suggests that they may sense and adapt to phosphate availability, although the precise mechanism for phosphate sensing in mammals remains unclear. Unicellular organisms, such as bacteria and yeast, use some types of Pitransporters and other molecules, such as kinases, to sense the environmental Piavailability. Multicellular animals may need to integrate signals from various organs to sense the phosphate levels as a whole organism, similarly to higher plants. Clarification of the phosphate-sensing mechanism in humans may lead to the development of new therapeutic strategies to prevent and treat diseases caused by phosphate imbalance.
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Affiliation(s)
- Toshimi Michigami
- Department of Bone and Mineral Research, Research Institute, Osaka Women’s and Children’s Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka, Japan; and Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Masanobu Kawai
- Department of Bone and Mineral Research, Research Institute, Osaka Women’s and Children’s Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka, Japan; and Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Miwa Yamazaki
- Department of Bone and Mineral Research, Research Institute, Osaka Women’s and Children’s Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka, Japan; and Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Keiichi Ozono
- Department of Bone and Mineral Research, Research Institute, Osaka Women’s and Children’s Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka, Japan; and Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
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Hernando N, Wagner CA. Mechanisms and Regulation of Intestinal Phosphate Absorption. Compr Physiol 2018; 8:1065-1090. [PMID: 29978897 DOI: 10.1002/cphy.c170024] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
States of hypo- and hyperphosphatemia have deleterious consequences including rickets/osteomalacia and renal/cardiovascular disease, respectively. Therefore, the maintenance of appropriate plasma levels of phosphate is an essential requirement for health. This control is executed by the collaborative action of intestine and kidney whose capacities to (re)absorb phosphate are regulated by a number of hormonal and metabolic factors, among them parathyroid hormone, fibroblast growth factor 23, 1,25(OH)2 vitamin D3 , and dietary phosphate. The molecular mechanisms responsible for the transepithelial transport of phosphate across enterocytes are only partially understood. Indeed, whereas renal reabsorption entirely relies on well-characterized active transport mechanisms of phosphate across the renal proximal epithelia, intestinal absorption proceeds via active and passive mechanisms, with the molecular identity of the passive component still unknown. The active absorption of phosphate depends mostly on the activity and expression of the sodium-dependent phosphate cotransporter NaPi-IIb (SLC34A2), which is highly regulated by many of the factors, mentioned earlier. Physiologically, the contribution of NaPi-IIb to the maintenance of phosphate balance appears to be mostly relevant during periods of low phosphate availability. Therefore, its role in individuals living in industrialized societies with high phosphate intake is probably less relevant. Importantly, small increases in plasma phosphate, even within normal range, associate with higher risk of cardiovascular disease. Therefore, therapeutic approaches to treat hyperphosphatemia, including dietary phosphate restriction and phosphate binders, aim at reducing intestinal absorption. Here we review the current state of research in the field. © 2017 American Physiological Society. Compr Physiol 8:1065-1090, 2018.
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Affiliation(s)
- Nati Hernando
- National Center for Competence in Research NCCR Kidney.CH, Institute of Physiology, University Zurich-Irchel, Zurich, Switzerland
| | - Carsten A Wagner
- National Center for Competence in Research NCCR Kidney.CH, Institute of Physiology, University Zurich-Irchel, Zurich, Switzerland
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30
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Watanabe H, Maruyama T. Role of Parathyroid Hormone in Regulating Transporter and Metabolizing Enzyme Function. Ther Apher Dial 2018; 22:251-254. [PMID: 29883064 DOI: 10.1111/1744-9987.12686] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Revised: 03/06/2018] [Accepted: 03/11/2018] [Indexed: 11/30/2022]
Abstract
Recent studies demonstrate that parathyroid hormone (PTH) not only maintains mineral homeostasis through targeting the kidneys and bone, but also exerts its effects on other organs. For instance, PTH induces urate accumulation through inhibiting the expression of the ABCG2 in both the intestine and the kidney. In addition, PTH downregulates the expression of cytochrome P450 (CYP) 3A, a major enzyme for drug metabolism in both the intestine and liver, resulting in the increase of substrate drug exposure. These functions of PTH are mediated through the PTH receptor (PTHR) signaling. Since PTHR exists in various organs, PTH may regulate other, still unspecified transporters or enzymes in the organs that express PTHR.
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Affiliation(s)
- Hiroshi Watanabe
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan
| | - Toru Maruyama
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan
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31
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Edwards A, Bonny O. A model of calcium transport and regulation in the proximal tubule. Am J Physiol Renal Physiol 2018; 315:F942-F953. [PMID: 29846115 PMCID: PMC6230728 DOI: 10.1152/ajprenal.00129.2018] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The objective of this study was to examine theoretically how Ca2+ reabsorption in the proximal tubule (PT) is modulated by Na+ and water fluxes, parathyroid hormone (PTH), Na+-glucose cotransporter (SGLT2) inhibitors, and acetazolamide. We expanded a previously published mathematical model of water and solute transport in the rat PT (Layton AT, Vallon V, Edwards A. Am J Physiol Renal Physiol 308: F1343–F1357, 2015) that did not include Ca2+. Our results indicate that Ca2+ reabsorption in the PT is primarily driven by the transepithelial Ca2+ concentration gradient that stems from water reabsorption, which is itself coupled to Na+ reabsorption. Simulated variations in permeability or transporter activity elicit opposite changes in paracellular and transcellular Ca2+ fluxes, whereas a simulated decrease in filtration rate lowers both fluxes. The model predicts that PTH-mediated inhibition of the apical Na+/H+ exchanger NHE3 reduces Na+ and Ca2+ transport to a similar extent. It also suggests that acetazolamide- and SGLT2 inhibitor-induced calciuria at least partly stems from reduced Ca2+ reabsorption in the PT. In addition, backleak of phosphate (PO4) across tight junctions is predicted to reduce net PO4 reabsorption by ~20% under normal conditions. When transcellular PO4 transport is substantially reduced by PTH, paracellular PO4 flux is reversed and contributes significantly to PO4 reabsorption. Furthermore, PTH is predicted to exert an indirect impact on PO4 reabsorption via its inhibitory action on NHE3. This model thus provides greater insight into the mechanisms that modulate Ca2+ and PO4 reabsorption in the PT.
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Affiliation(s)
- Aurélie Edwards
- Department of Biomedical Engineering, Boston University , Boston, Massachusetts
| | - Olivier Bonny
- Department of Pharmacology and Toxicology, University of Lausanne, and Service of Nephrology, Lausanne University Hospital , Lausanne , Switzerland
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32
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Turner ME, White CA, Hopman WM, Ward EC, Jeronimo PS, Adams MA, Holden RM. Impaired Phosphate Tolerance Revealed With an Acute Oral Challenge. J Bone Miner Res 2018; 33:113-122. [PMID: 28914962 DOI: 10.1002/jbmr.3294] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 08/28/2017] [Accepted: 09/13/2017] [Indexed: 01/01/2023]
Abstract
Elevated serum phosphate is consistently linked with cardiovascular disease (CVD) events and mortality in the setting of normal and impaired kidney function. However, serum phosphate does not often exceed the upper limit of normal until glomerular filtration rate (GFR) falls below 30 mL/min/m2 . It was hypothesized that the response to an oral, bioavailable phosphate load will unmask impaired phosphate tolerance, a maladaptation not revealed by baseline serum phosphate concentrations. In this study, rats with varying kidney function as well as normo-phosphatemic human subjects, with inulin-measured GFR (13.2 to 128.3mL/min), received an oral phosphate load. Hormonal and urinary responses were evaluated over 2 hours. Results revealed that the more rapid elevation of serum phosphate was associated with subjects and rats with higher levels of kidney function, greater responsiveness to acute changes in parathyroid hormone (PTH), and significantly more urinary phosphate at 2 hours. In humans, increases in urinary phosphate to creatinine ratio did not correlate with baseline serum phosphate concentrations but did correlate strongly to early increase of serum phosphate. The blunted rise in serum phosphate in rats with CKD was not the result of altered absorption. This result suggests acute tissue deposition may be altered in the setting of kidney function impairment. Early recognition of impaired phosphate tolerance could translate to important interventions, such as dietary phosphate restriction or phosphate binders, being initiated at much higher levels of kidney function than is current practice. © 2017 American Society for Bone and Mineral Research.
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Affiliation(s)
- Mandy E Turner
- Department of Biomedical and Molecular Science, Queen's University, Kingston, Canada
| | | | - Wilma M Hopman
- Clinical Research Centre, Kingston General Hospital, Kingston, Canada.,Department of Public Health Sciences, Queen's University, Kingston, Canada
| | - Emilie C Ward
- Department of Biomedical and Molecular Science, Queen's University, Kingston, Canada
| | - Paul S Jeronimo
- Department of Biomedical and Molecular Science, Queen's University, Kingston, Canada
| | - Michael A Adams
- Department of Biomedical and Molecular Science, Queen's University, Kingston, Canada
| | - Rachel M Holden
- Department of Biomedical and Molecular Science, Queen's University, Kingston, Canada.,Department of Medicine, Queen's University, Kingston, Canada
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Lee JJ, Plain A, Beggs MR, Dimke H, Alexander RT. Effects of phospho- and calciotropic hormones on electrolyte transport in the proximal tubule. F1000Res 2017; 6:1797. [PMID: 29043081 PMCID: PMC5627579 DOI: 10.12688/f1000research.12097.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/04/2017] [Indexed: 12/17/2022] Open
Abstract
Calcium and phosphate are critical for a myriad of physiological and cellular processes within the organism. Consequently, plasma levels of calcium and phosphate are tightly regulated. This occurs through the combined effects of the phospho- and calciotropic hormones, parathyroid hormone (PTH), active vitamin D
3, and fibroblast growth factor 23 (FGF23). The organs central to this are the kidneys, intestine, and bone. In the kidney, the proximal tubule reabsorbs the majority of filtered calcium and phosphate, which amounts to more than 60% and 90%, respectively. The basic molecular mechanisms responsible for phosphate reclamation are well described, and emerging work is delineating the molecular identity of the paracellular shunt wherein calcium permeates the proximal tubular epithelium. Significant experimental work has delineated the molecular effects of PTH and FGF23 on these processes as well as their regulation of active vitamin D
3 synthesis in this nephron segment. The integrative effects of both phospho- and calciotropic hormones on proximal tubular solute transport and subsequently whole body calcium-phosphate balance thus have been further complicated. Here, we first review the molecular mechanisms of calcium and phosphate reabsorption from the proximal tubule and how they are influenced by the phospho- and calciotropic hormones acting on this segment and then consider the implications on both renal calcium and phosphate handling as well as whole body mineral balance.
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Affiliation(s)
- Justin J Lee
- Department of Physiology, University of Alberta, Edmonton, Canada.,The Women and Children's Health Research Institute, Edmonton, Canada
| | - Allein Plain
- Department of Physiology, University of Alberta, Edmonton, Canada.,The Women and Children's Health Research Institute, Edmonton, Canada
| | - Megan R Beggs
- Department of Physiology, University of Alberta, Edmonton, Canada.,The Women and Children's Health Research Institute, Edmonton, Canada
| | - Henrik Dimke
- Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - R Todd Alexander
- Department of Physiology, University of Alberta, Edmonton, Canada.,The Women and Children's Health Research Institute, Edmonton, Canada.,Department of Pediatrics, Edmonton Clinic Health Academy, University of Alberta, Edmonton, Canada
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34
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Parathyroid hormone contributes to the down-regulation of cytochrome P450 3A through the cAMP/PI3K/PKC/PKA/NF-κB signaling pathway in secondary hyperparathyroidism. Biochem Pharmacol 2017; 145:192-201. [PMID: 28843775 DOI: 10.1016/j.bcp.2017.08.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 08/21/2017] [Indexed: 11/24/2022]
Abstract
Chronic kidney disease (CKD), which affects, not only renal clearance, but also non-renal clearance, is accompanied by a decline in renal function. Although it has been suggested that humoral factors, such as uremic toxins that accumulate in the body under CKD conditions, could be involved in the changes associated with non-renal drug clearance, the overall process is not completely understood. In this study, we report on the role of parathyroid hormone (PTH), a middle molecule uremic toxin, on the expression of drug metabolizing or transporting proteins using rats with secondary hyperparathyroidism (SHPT) as models. In SHPT rats, hepatic and intestinal CYP3A expression was suppressed, but the changes were recovered by the administration of the calcimimetic cinacalcet, a PTH suppressor. Under the same experimental conditions, a pharmacokinetic study using orally administered midazolam, a substrate for CYP3A, showed that the AUC was increased by 5 times in SHPT rats, but that was partially recovered by a cinacalcet treatment. This was directly tested in rat primary hepatocytes and intestinal Caco-2 cells where the expression of the CYP3A protein was down-regulated by PTH (1-34). In Caco-2 cells, PTH (1-34) down-regulated the expression of CYP3A mRNA, but an inactive PTH derivative (13-34) had no effect. 8-Bromo-cyclic adenosine monophosphate, a membrane-permeable cAMP analog, reduced mRNA expression of CYP3A whereas the inhibitors of PI3K, NF-κB, PKC and PKA reversed the PTH-induced CYP3A down-regulation. These results suggest that PTH down-regulates CYP3A through multiple signaling pathways, including the PI3K/PKC/PKA/NF-κB pathway after the elevation of intracellular cAMP, and the effect of PTH can be prevented by cinacalcet treatment.
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35
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Bastepe M, Turan S, He Q. Heterotrimeric G proteins in the control of parathyroid hormone actions. J Mol Endocrinol 2017; 58:R203-R224. [PMID: 28363951 PMCID: PMC5650080 DOI: 10.1530/jme-16-0221] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 02/17/2017] [Indexed: 12/17/2022]
Abstract
Parathyroid hormone (PTH) is a key regulator of skeletal physiology and calcium and phosphate homeostasis. It acts on bone and kidney to stimulate bone turnover, increase the circulating levels of 1,25 dihydroxyvitamin D and calcium and inhibit the reabsorption of phosphate from the glomerular filtrate. Dysregulated PTH actions contribute to or are the cause of several endocrine disorders. This calciotropic hormone exerts its actions via binding to the PTH/PTH-related peptide receptor (PTH1R), which couples to multiple heterotrimeric G proteins, including Gs and Gq/11 Genetic mutations affecting the activity or expression of the alpha-subunit of Gs, encoded by the GNAS complex locus, are responsible for several human diseases for which the clinical findings result, at least partly, from aberrant PTH signaling. Here, we review the bone and renal actions of PTH with respect to the different signaling pathways downstream of these G proteins, as well as the disorders caused by GNAS mutations.
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Affiliation(s)
- Murat Bastepe
- Endocrine UnitDepartment of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Serap Turan
- Department of Pediatric EndocrinologyMarmara University School of Medicine, Istanbul, Turkey
| | - Qing He
- Endocrine UnitDepartment of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
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36
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Christopoulou EC, Filippatos TD, Megapanou E, Elisaf MS, Liamis G. Phosphate imbalance in patients with heart failure. Heart Fail Rev 2017; 22:349-356. [DOI: 10.1007/s10741-017-9615-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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37
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Sugimoto R, Watanabe H, Ikegami K, Enoki Y, Imafuku T, Sakaguchi Y, Murata M, Nishida K, Miyamura S, Ishima Y, Tanaka M, Matsushita K, Komaba H, Fukagawa M, Otagiri M, Maruyama T. Down-regulation of ABCG2, a urate exporter, by parathyroid hormone enhances urate accumulation in secondary hyperparathyroidism. Kidney Int 2017; 91:658-670. [DOI: 10.1016/j.kint.2016.09.041] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 09/20/2016] [Accepted: 09/29/2016] [Indexed: 12/21/2022]
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38
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Tatsumi S, Miyagawa A, Kaneko I, Shiozaki Y, Segawa H, Miyamoto KI. Regulation of renal phosphate handling: inter-organ communication in health and disease. J Bone Miner Metab 2016; 34:1-10. [PMID: 26296817 DOI: 10.1007/s00774-015-0705-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 07/16/2015] [Indexed: 01/18/2023]
Abstract
In this review, we focus on the interconnection of inorganic phosphate (Pi) homeostasis in the network of the bone-kidney, parathyroid-kidney, intestine-kidney, and liver-kidney axes. Such a network of organ communication is important for body Pi homeostasis. Normalization of serum Pi levels is a clinical target in patients with chronic kidney disease (CKD). Particularly, disorders of the fibroblast growth factor 23/klotho system are observed in early CKD. Identification of phosphaturic factors from the intestine and liver may enhance our understanding of body Pi homeostasis and Pi metabolism disturbances in CKD patients.
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Affiliation(s)
- Sawako Tatsumi
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Atsumi Miyagawa
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Ichiro Kaneko
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Yuji Shiozaki
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Hiroko Segawa
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Ken-Ichi Miyamoto
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan.
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Suda T, Masuyama R, Bouillon R, Carmeliet G. Physiological functions of vitamin D: what we have learned from global and conditional VDR knockout mouse studies. Curr Opin Pharmacol 2015; 22:87-99. [PMID: 25938686 DOI: 10.1016/j.coph.2015.04.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 04/01/2015] [Accepted: 04/12/2015] [Indexed: 12/25/2022]
Abstract
The physiological role of vitamin D depends on calcium supply and calcium balance. When the calcium balance is normal, the major target of vitamin D is intestine. Vitamin D stimulates mainly active intestinal calcium transport mechanism. During a negative calcium balance, bone effects of vitamin D become dominant. Thus, the role of vitamin D in maintaining normocalcemia appears to have priority over skeletal integrity in these situations.
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Affiliation(s)
- Tatsuo Suda
- Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan.
| | - Ritsuko Masuyama
- Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Roger Bouillon
- Clinical and Experimental Endocrinology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Geert Carmeliet
- Clinical and Experimental Endocrinology, Katholieke Universiteit Leuven, Leuven, Belgium
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40
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Evaluation of intestinal phosphate binding to improve the safety profile of oral sodium phosphate bowel cleansing. PLoS One 2015; 10:e0116590. [PMID: 25790436 PMCID: PMC4366239 DOI: 10.1371/journal.pone.0116590] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 12/11/2014] [Indexed: 01/16/2023] Open
Abstract
Prior to colonoscopy, bowel cleansing is performed for which frequently oral sodium phosphate (OSP) is used. OSP results in significant hyperphosphatemia and cases of acute kidney injury (AKI) referred to as acute phosphate nephropathy (APN; characterized by nephrocalcinosis) are reported after OSP use, which led to a US-FDA warning. To improve the safety profile of OSP, it was evaluated whether the side-effects of OSP could be prevented with intestinal phosphate binders. Hereto a Wistar rat model of APN was developed. OSP administration (2 times 1.2 g phosphate by gavage) with a 12h time interval induced bowel cleansing (severe diarrhea) and significant hyperphosphatemia (21.79 ± 5.07 mg/dl 6h after the second OSP dose versus 8.44 ± 0.97 mg/dl at baseline). Concomitantly, serum PTH levels increased fivefold and FGF-23 levels showed a threefold increase, while serum calcium levels significantly decreased from 11.29 ± 0.53 mg/dl at baseline to 8.68 ± 0.79 mg/dl after OSP. OSP administration induced weaker NaPi-2a staining along the apical proximal tubular membrane. APN was induced: serum creatinine increased (1.5 times baseline) and nephrocalcinosis developed (increased renal calcium and phosphate content and calcium phosphate deposits on Von Kossa stained kidney sections). Intestinal phosphate binding (lanthanum carbonate or aluminum hydroxide) was not able to attenuate the OSP induced side-effects. In conclusion, a clinically relevant rat model of APN was developed. Animals showed increased serum phosphate levels similar to those reported in humans and developed APN. No evidence was found for an improved safety profile of OSP by using intestinal phosphate binders.
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Fenton RA, Murray F, Dominguez Rieg JA, Tang T, Levi M, Rieg T. Renal phosphate wasting in the absence of adenylyl cyclase 6. J Am Soc Nephrol 2014; 25:2822-34. [PMID: 24854272 PMCID: PMC4243352 DOI: 10.1681/asn.2013101102] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 03/31/2014] [Indexed: 11/03/2022] Open
Abstract
Parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF-23) enhance phosphate excretion by the proximal tubule of the kidney by retrieval of the sodium-dependent phosphate transporters (Npt2a and Npt2c) from the apical plasma membrane. PTH activates adenylyl cyclase (AC) through PTH 1 receptors and stimulates the cAMP/PKA signaling pathway. However, the precise role and isoform(s) of AC in phosphate homeostasis are not known. We report here that mice lacking AC6 (AC6(-/-)) have increased plasma PTH and FGF-23 levels compared with wild-type (WT) mice but comparable plasma phosphate concentrations. Acute activation of the calcium-sensing receptor or feeding a zero phosphate diet almost completely suppressed plasma PTH levels in both AC6(-/-) and WT mice, indicating a secondary cause for hyperparathyroidism. Pharmacologic blockade of FGF receptors resulted in a comparable increase in plasma phosphate between genotypes, whereas urinary phosphate remained significantly higher in AC6(-/-) mice. Compared with WT mice, AC6(-/-) mice had reduced renal Npt2a and Npt2c protein abundance, with approximately 80% of Npt2a residing in lysosomes. WT mice responded to exogenous PTH with redistribution of Npt2a from proximal tubule microvilli to intracellular compartments and lysosomes alongside a PTH-induced dose-response relationship for fractional phosphate excretion and urinary cAMP excretion. These responses were absent in AC6(-/-) mice. In conclusion, AC6 in the proximal tubule modulates cAMP formation, Npt2a trafficking, and urinary phosphate excretion, which are highlighted by renal phosphate wasting in AC6(-/-) mice.
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Affiliation(s)
- Robert A Fenton
- Interactions of Proteins in Epithelial Transport Center, Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Fiona Murray
- Department of Medicine, University of California San Diego, La Jolla, California
| | | | - Tong Tang
- Veterans Affairs San Diego Healthcare System, San Diego, California; and
| | - Moshe Levi
- Department of Medicine, University of Colorado Denver, Aurora, Colorado
| | - Timo Rieg
- Department of Medicine, University of California San Diego, La Jolla, California; Veterans Affairs San Diego Healthcare System, San Diego, California; and
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42
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Lu KC, Wu CC, Yen JF, Liu WC. Vascular calcification and renal bone disorders. ScientificWorldJournal 2014; 2014:637065. [PMID: 25136676 PMCID: PMC4127293 DOI: 10.1155/2014/637065] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2014] [Revised: 06/15/2014] [Accepted: 06/28/2014] [Indexed: 12/11/2022] Open
Abstract
At the early stage of chronic kidney disease (CKD), the systemic mineral metabolism and bone composition start to change. This alteration is known as chronic kidney disease-mineral bone disorder (CKD-MBD). It is well known that the bone turnover disorder is the most common complication of CKD-MBD. Besides, CKD patients usually suffer from vascular calcification (VC), which is highly associated with mortality. Many factors regulate the VC mechanism, which include imbalances in serum calcium and phosphate, systemic inflammation, RANK/RANKL/OPG triad, aldosterone, microRNAs, osteogenic transdifferentiation, and effects of vitamins. These factors have roles in both promoting and inhibiting VC. Patients with CKD usually have bone turnover problems. Patients with high bone turnover have increase of calcium and phosphate release from the bone. By contrast, when bone turnover is low, serum calcium and phosphate levels are frequently maintained at high levels because the reservoir functions of bone decrease. Both of these conditions will increase the possibility of VC. In addition, the calcified vessel may secrete FGF23 and Wnt inhibitors such as sclerostin, DKK-1, and secreted frizzled-related protein to prevent further VC. However, all of them may fight back the inhibition of bone formation resulting in fragile bone. There are several ways to treat VC depending on the bone turnover status of the individual. The main goals of therapy are to maintain normal bone turnover and protect against VC.
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Affiliation(s)
- Kuo-Cheng Lu
- Division of Nephrology, Department of Medicine, Cardinal Tien Hospital, School of Medicine, Fu Jen Catholic University, New Taipei City 23148, Taiwan
| | - Chia-Chao Wu
- Division of Nephrology, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei 114, Taiwan
| | - Jen-Fen Yen
- Division of Nephrology, Department of Internal Medicine, Yonghe Cardinal Tien Hospital, 80 Zhongxing Street, Yonghe District, New Taipei City 23445, Taiwan
| | - Wen-Chih Liu
- Division of Nephrology, Department of Internal Medicine, Yonghe Cardinal Tien Hospital, 80 Zhongxing Street, Yonghe District, New Taipei City 23445, Taiwan
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Uwai Y, Arima R, Takatsu C, Furuta R, Kawasaki T, Nabekura T. Sodium-phosphate cotransporter mediates reabsorption of lithium in rat kidney. Pharmacol Res 2014; 87:94-8. [PMID: 24997387 DOI: 10.1016/j.phrs.2014.06.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Revised: 06/24/2014] [Accepted: 06/24/2014] [Indexed: 01/28/2023]
Abstract
Lithium, used for the treatment of bipolar disorders, is reabsorbed via sodium-transport system in the proximal tubule. This step causes intra-/inter-individual difference of lithium disposition, and it has not been unclear which transporter contributes. In this study, we examined effect of foscarnet and parathyroid hormone (PTH), inactivators for sodium-phosphate cotransporter, and phlorizin, a typical inhibitor for sodium-glucose cotransporter, on the disposition of lithium in rats. Their intravenous administration stimulated urinary excretion of phosphate or glucose. After the intravenous injection of lithium chloride as a bolus, plasma concentration of lithium decreased time-dependently. The renal clearance of lithium was calculated to be 0.740 ml/min/kg in control rats, and this was 26.7% of creatinine clearance. Foscarnet and PTH significantly increased the renal clearance of lithium and its ratio to creatinine clearance, suggesting that they prevented the reabsorption of lithium. No effect of phlorizin on the renal handling of lithium was recognized. In control rats, the renal clearance of lithium showed a strong correlation with the renal excretion rate of phosphate, compared with creatinine clearance. These findings suggest that sodium-phosphate cotransporter reabsorbs lithium in the rat kidney. Furthermore, its contribution was estimated to be more than 65.9% in the lithium reabsorption. And, this study raised the possibility that therapeutic outcome of lithium is related with the functional expression of sodium-phosphate cotransporter in the kidney.
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Affiliation(s)
- Yuichi Uwai
- Department of Pharmaceutics, School of Pharmacy, Aichi Gakuin University, Nagoya, Japan.
| | - Ryosuke Arima
- Department of Pharmaceutics, School of Pharmacy, Aichi Gakuin University, Nagoya, Japan
| | - Chihiro Takatsu
- Department of Pharmaceutics, School of Pharmacy, Aichi Gakuin University, Nagoya, Japan
| | - Ryo Furuta
- Department of Pharmaceutics, School of Pharmacy, Aichi Gakuin University, Nagoya, Japan
| | - Tatsuya Kawasaki
- Department of Pharmaceutics, School of Pharmacy, Aichi Gakuin University, Nagoya, Japan
| | - Tomohiro Nabekura
- Department of Pharmaceutics, School of Pharmacy, Aichi Gakuin University, Nagoya, Japan
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Biber J, Murer H, Mohebbi N, Wagner C. Renal Handling of Phosphate and Sulfate. Compr Physiol 2014; 4:771-92. [DOI: 10.1002/cphy.c120031] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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45
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Myakala K, Motta S, Murer H, Wagner CA, Koesters R, Biber J, Hernando N. Renal-specific and inducible depletion of NaPi-IIc/Slc34a3, the cotransporter mutated in HHRH, does not affect phosphate or calcium homeostasis in mice. Am J Physiol Renal Physiol 2014; 306:F833-43. [PMID: 24553430 DOI: 10.1152/ajprenal.00133.2013] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The proximal renal epithelia express three different Na-dependent inorganic phosphate (Pi) cotransporters: NaPi-IIa/SLC34A1, NaPi-IIc/SLC34A3, and PiT2/SLC20A2. Constitutive mouse knockout models of NaPi-IIa and NaPi-IIc suggested that NaPi-IIa mediates the bulk of renal reabsorption of Pi whereas the contribution of NaPi-IIc to this process is minor and probably restricted to young mice. However, many reports indicate that mutations of NaPi-IIc in humans lead to hereditary hypophosphatemic rickets with hypercalciuria (HHRH). Here, we report the generation of a kidney-specific and inducible NaPi-IIc-deficient mouse model based on the loxP-Cre system. We found that the specific removal of the cotransporter from the kidneys of young mice does not impair the capacity of the renal epithelia to transport Pi. Moreover, the levels of Pi in plasma and urine as well as the circulating levels of parathyroid hormone, FGF-23, and vitamin D3 remained unchanged. These findings are in agreement with the data obtained with the constitutive knockout model and suggest that, under steady-state conditions of normal dietary Pi, NaPi-IIc is not an essential Na-Pi cotransporter in murine kidneys. However, and unlike the constitutive mutants, the kidney-specific depletion of NaPi-IIc does not result in alteration of the homeostasis of calcium. This suggests that the calcium-related phenotype observed in constitutive knockout mice may not be related to inactivation of the cotransporter in kidney.
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Affiliation(s)
- Komuraiah Myakala
- Institute of Physiology and Zurich Center for Integrative Human Physiology. Univ. of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
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Ikeda S, Yamamoto H, Masuda M, Takei Y, Nakahashi O, Kozai M, Tanaka S, Nakao M, Taketani Y, Segawa H, Iwano M, Miyamoto KI, Takeda E. Downregulation of renal type IIa sodium-dependent phosphate cotransporter during lipopolysaccharide-induced acute inflammation. Am J Physiol Renal Physiol 2014; 306:F744-50. [PMID: 24500689 DOI: 10.1152/ajprenal.00474.2013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The type IIa sodium-dependent phosphate cotransporter (Npt2a) plays a critical role in reabsorption of inorganic phosphate (Pi) by renal proximal tubular cells. Pi abnormalities during early stages of sepsis have been reported, but the mechanisms regulating Pi homeostasis during acute inflammation are poorly understood. We examined the regulation of Pi metabolism and renal Npt2a expression during lipopolysaccharide (LPS)-induced inflammation in mice. Dose-response and time-course studies with LPS showed significant increases of plasma Pi and intact parathyroid hormone (iPTH) levels and renal Pi excretion, while renal calcium excretion was significantly decreased. There was no difference in plasma 1,25-dihydroxyvitamin D levels, but the induction of plasma intact fibroblast growth factor 23 levels peaked 3 h after LPS treatment. Western blotting, immunostaining, and quantitative real-time PCR showed that LPS administration significantly decreased Npt2a protein expression in the brush border membrane (BBM) 3 h after injection, but there was no change in renal Npt2a mRNA levels. Moreover, tumor necrosis factor-α injection also increased plasma iPTH and decreased renal BBM Npt2a expression. Importantly, we revealed that parathyroidectomized rats had impaired renal Pi excretion and BBM Npt2a expression in response to LPS. These results suggest that the downregulation of Npt2a expression in renal BBM through induction of plasma iPTH levels alter Pi homeostasis during LPS-induced acute inflammation.
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Affiliation(s)
- Shoko Ikeda
- Dept. of Health and Nutrition, Faculty of Human Life, Jin-ai Univ., Ohde-cho 3-1-1, Echizen city, Fukui 915-8586, Japan.
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47
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The SLC34 family of sodium-dependent phosphate transporters. Pflugers Arch 2013; 466:139-53. [PMID: 24352629 DOI: 10.1007/s00424-013-1418-6] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Revised: 12/01/2013] [Accepted: 12/02/2013] [Indexed: 12/27/2022]
Abstract
The SLC34 family of sodium-driven phosphate cotransporters comprises three members: NaPi-IIa (SLC34A1), NaPi-IIb (SLC34A2), and NaPi-IIc (SLC34A3). These transporters mediate the translocation of divalent inorganic phosphate (HPO4 (2-)) together with two (NaPi-IIc) or three sodium ions (NaPi-IIa and NaPi-IIb), respectively. Consequently, phosphate transport by NaPi-IIa and NaPi-IIb is electrogenic. NaPi-IIa and NaPi-IIc are predominantly expressed in the brush border membrane of the proximal tubule, whereas NaPi-IIb is found in many more organs including the small intestine, lung, liver, and testis. The abundance and activity of these transporters are mostly regulated by changes in their expression at the cell surface and are determined by interactions with proteins involved in scaffolding, trafficking, or intracellular signaling. All three transporters are highly regulated by factors including dietary phosphate status, hormones like parathyroid hormone, 1,25-OH2 vitamin D3 or FGF23, electrolyte, and acid-base status. The physiological relevance of the three members of the SLC34 family is underlined by rare Mendelian disorders causing phosphaturia, hypophosphatemia, or ectopic organ calcifications.
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Nomura K, Tatsumi S, Miyagawa A, Shiozaki Y, Sasaki S, Kaneko I, Ito M, Kido S, Segawa H, Sano M, Fukuwatari T, Shibata K, Miyamoto KI. Hepatectomy-related hypophosphatemia: a novel phosphaturic factor in the liver-kidney axis. J Am Soc Nephrol 2013; 25:761-72. [PMID: 24262791 DOI: 10.1681/asn.2013060569] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Marked hypophosphatemia is common after major hepatic resection, but the pathophysiologic mechanism remains unknown. We used a partial hepatectomy (PH) rat model to investigate the molecular basis of hypophosphatemia. PH rats exhibited hypophosphatemia and hyperphosphaturia. In renal and intestinal brush-border membrane vesicles isolated from PH rats, Na(+)-dependent phosphate (Pi) uptake decreased by 50%-60%. PH rats also exhibited significantly decreased levels of renal and intestinal Na(+)-dependent Pi transporter proteins (NaPi-IIa [NaPi-4], NaPi-IIb, and NaPi-IIc). Parathyroid hormone was elevated at 6 hours after PH. Hyperphosphaturia persisted, however, even after thyroparathyroidectomy in PH rats. Moreover, DNA microarray data revealed elevated levels of nicotinamide phosphoribosyltransferase (Nampt) mRNA in the kidney after PH, and Nampt protein levels and total NAD concentration increased significantly in the proximal tubules. PH rats also exhibited markedly increased levels of the Nampt substrate, urinary nicotinamide (NAM), and NAM catabolites. In vitro analyses using opossum kidney cells revealed that NAM alone did not affect endogenous NaPi-4 levels. However, in cells overexpressing Nampt, the addition of NAM led to a marked decrease in cell surface expression of NaPi-4 that was blocked by treatment with FK866, a specific Nampt inhibitor. Furthermore, FK866-treated mice showed elevated renal Pi reabsorption and hypophosphaturia. These findings indicate that hepatectomy-induced hypophosphatemia is due to abnormal NAM metabolism, including Nampt activation in renal proximal tubular cells.
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Affiliation(s)
- Kengo Nomura
- Department of Molecular Nutrition Institution of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan; and
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Lau WL, Ix JH. Clinical detection, risk factors, and cardiovascular consequences of medial arterial calcification: a pattern of vascular injury associated with aberrant mineral metabolism. Semin Nephrol 2013; 33:93-105. [PMID: 23465497 DOI: 10.1016/j.semnephrol.2012.12.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Patients with end-stage renal disease are characterized by extensive vascular calcification and high cardiovascular disease (CVD) risk. Calcification in end-stage renal disease patients represents at least two distinct pathologic processes. Calcification within the tunica intima frequently is associated with lipid-laden, flow-limiting atherosclerotic plaques. These appear as spotty areas of calcification interspersed with noncalcified arterial segments on plain radiography and generally are found near arterial branch points in medium-sized conduit arteries. In contrast, medial arterial calcification (MAC) involves deeper layers of the arterial wall; tends to affect the artery diffusely, appearing as a linear contiguous tram-track pattern of calcification on plain radiography; and often involves smaller muscular arteries such as the radial artery, intermammary arteries, and arteries in the ankle and foot. Both are related to CVD events, but potentially through different mechanisms. Atherosclerotic calcification may be marking the total burden of atherosclerosis, whereas MAC may lead to arterial stiffness and left ventricular hypertrophy. Existing data suggest that altered mineral metabolism may promote MAC, whereas heightened inflammation and oxidative stress contribute to atherosclerosis. Dysregulation of normal anticalcification factors and elastin degradation are common to both processes. Risk of vascular calcification also may be increased by the use of certain medications in the setting of chronic kidney disease. This review compares and contrasts known risk factors for MAC and atherosclerosis, describes existing and emerging technologies to distinguish between them, and reviews the existing literature linking each with CVD events in dialysis patients and in other settings.
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Affiliation(s)
- Wei Ling Lau
- Division of Nephrology, Department of Medicine, University of Washington, Seattle, WA, USA
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50
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Guo J, Song L, Liu M, Segawa H, Miyamoto KI, Bringhurst FR, Kronenberg HM, Jüppner H. Activation of a non-cAMP/PKA signaling pathway downstream of the PTH/PTHrP receptor is essential for a sustained hypophosphatemic response to PTH infusion in male mice. Endocrinology 2013; 154:1680-9. [PMID: 23515284 PMCID: PMC3628020 DOI: 10.1210/en.2012-2240] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
PTH increases urinary Pi excretion by reducing expression of two renal cotransporters [NaPi-IIa (Npt2a) and NaPi-IIc (Npt2c)]. In contrast to acute transporter regulation that is cAMP/protein kinase A dependent, long-term effects require phospholipase C (PLC) signaling by the PTH/PTHrP receptor (PPR). To determine whether the latter pathway regulates Pi through Npt2a and/or Npt2c, wild-type mice (Wt) and animals expressing a mutant PPR incapable of PLC activation (DD) were tested in the absence of one (Npt2a(-/-) or Npt2c(-/-)) or both phosphate transporters (2a/2c-dko). PTH infusion for 8 days caused a rapid and persistent decrease in serum Pi in Wt mice, whereas serum Pi in DD mice fell only transiently for the first 2 days. Consistent with these findings, fractional Pi excretion index was increased initially in both animals, but this increase persisted only when the PPR Wt was present. The hypophosphatemic response to PTH infusion was impaired only slightly in PPR Wt/Npt2c(-/-) or DD/Npt2c(-/-) mice. Despite lower baselines, PTH infusion in PPR Wt/Npt2a(-/-) mice decreased serum Pi further, an effect that was attenuated in DD/Npt2a(-/-) mice. Continuous PTH had no effect on serum Pi in 2a/2c-dko mice. PTH administration increased serum 1,25 dihydroxyvitamin D3 levels in Wt and DD mice and increased levels above the elevated baseline with ablation of either but not of both transporters. Continuous PTH elevated serum fibroblast growth factor 23 and blood Ca(2+) equivalently in all groups of mice. Our data indicate that PLC signaling at the PPR contributes to the long-term effect of PTH on Pi homeostasis but not to the regulation of 1,25 dihydroxyvitamin D3, fibroblast growth factor 23, or blood Ca(2+).
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MESH Headings
- Animals
- Cyclic AMP/metabolism
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Hypophosphatemia/chemically induced
- Hypophosphatemia/genetics
- Hypophosphatemia/metabolism
- Infusions, Intravenous
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mutation/physiology
- Parathyroid Hormone/administration & dosage
- Parathyroid Hormone/adverse effects
- Parathyroid Hormone/metabolism
- Receptor, Parathyroid Hormone, Type 1/genetics
- Receptor, Parathyroid Hormone, Type 1/metabolism
- Receptor, Parathyroid Hormone, Type 1/physiology
- Signal Transduction/genetics
- Signal Transduction/physiology
- Sodium-Phosphate Cotransporter Proteins, Type IIa/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIa/metabolism
- Sodium-Phosphate Cotransporter Proteins, Type IIc/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIc/metabolism
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Affiliation(s)
- Jun Guo
- Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
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