1
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Yadav PS, Papaioannou G, Kobelski MM, Demay MB. Phosphate-induced activation of VEGFR2 leads to caspase-9-mediated apoptosis of hypertrophic chondrocytes. iScience 2023; 26:107548. [PMID: 37636062 PMCID: PMC10450517 DOI: 10.1016/j.isci.2023.107548] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 06/21/2023] [Accepted: 08/02/2023] [Indexed: 08/29/2023] Open
Abstract
Low circulating phosphate (Pi) leads to rickets, characterized by expansion of the hypertrophic chondrocytes (HCs) in the growth plate due to impaired HC apoptosis. Studies in HCs demonstrate that Pi activates the Raf/MEK/ERK1/2 and mitochondrial apoptotic pathways. To determine how Pi activates these pathways, a small-molecule screen was undertaken to identify inhibitors of Pi-induced ERK1/2 phosphorylation in HCs. Vascular endothelial growth factor receptor 2 (VEGFR2) was identified as a target. In vitro studies in HCs demonstrate that VEGFR2 inhibitors block Pi-induced pERK1/2 and caspase-9 cleavage. Like Pi, rhVEGF activates ERK1/2 and caspase-9 in HCs and induces phosphorylation of VEGFR2, confirming that Pi activates this signaling pathway in HCs. Chondrocyte-specific depletion of VEGFR2 leads to an increase in HCs, impaired vascular invasion, and a decrease in HC apoptosis. Thus, these studies define a role for VEGFR2 in transducing Pi signals and mediating its effects on growth plate maturation.
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Affiliation(s)
- Prem Swaroop Yadav
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA
- Harvard Medical School, Boston, MA, USA
| | - Garyfallia Papaioannou
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA
- Harvard Medical School, Boston, MA, USA
| | | | - Marie B. Demay
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA
- Harvard Medical School, Boston, MA, USA
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2
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Insights into the Molecular and Hormonal Regulation of Complications of X-Linked Hypophosphatemia. ENDOCRINES 2023. [DOI: 10.3390/endocrines4010014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023] Open
Abstract
X-linked hypophosphatemia (XLH) is characterized by mutations in the PHEX gene, leading to elevated serum levels of FGF23, decreased production of 1,25 dihydroxyvitamin D3 (1,25D), and hypophosphatemia. Those affected with XLH manifest impaired growth and skeletal and dentoalveolar mineralization as well as increased mineralization of the tendon–bone attachment site (enthesopathy), all of which lead to decreased quality of life. Many molecular and murine studies have detailed the role of mineral ions and hormones in regulating complications of XLH, including how they modulate growth and growth plate maturation, bone mineralization and structure, osteocyte-mediated mineral matrix resorption and canalicular organization, and enthesopathy development. While these studies have provided insight into the molecular underpinnings of these skeletal processes, current therapies available for XLH do not fully prevent or treat these complications. Therefore, further investigations are needed to determine the molecular pathophysiology underlying the complications of XLH.
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3
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Yuan Y, Jagga S, Martins JS, Rana R, Pajevic PD, Liu ES. Impaired 1,25 dihydroxyvitamin D3 action and hypophosphatemia underlie the altered lacuno-canalicular remodeling observed in the Hyp mouse model of XLH. PLoS One 2021; 16:e0252348. [PMID: 34043707 PMCID: PMC8158930 DOI: 10.1371/journal.pone.0252348] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 05/12/2021] [Indexed: 11/28/2022] Open
Abstract
Osteocytes remodel the perilacunar matrix and canaliculi. X-linked hypophosphatemia (XLH) is characterized by elevated serum levels of fibroblast growth factor 23 (FGF23), leading to decreased 1,25 dihydroxyvitamin D3 (1,25D) production and hypophosphatemia. Bones from mice with XLH (Hyp) have enlarged osteocyte lacunae, enhanced osteocyte expression of genes of bone remodeling, and impaired canalicular structure. The altered lacuno-canalicular (LCN) phenotype is improved with 1,25D or anti-FGF23 antibody treatment, pointing to roles for 1,25D and/or phosphate in regulating this process. To address whether impaired 1,25D action results in LCN alterations, the LCN phenotype was characterized in mice lacking the vitamin D receptor (VDR) in osteocytes (VDRf/f;DMP1Cre+). Mice lacking the sodium phosphate transporter NPT2a (NPT2aKO) have hypophosphatemia and high serum 1,25D levels, therefore the LCN phenotype was characterized in these mice to determine if increased 1,25D compensates for hypophosphatemia in regulating LCN remodeling. Unlike Hyp mice, neither VDRf/f;DMP1Cre+ nor NPT2aKO mice have dramatic alterations in cortical microarchitecture, allowing for dissecting 1,25D and phosphate specific effects on LCN remodeling in tibial cortices. Histomorphometric analyses demonstrate that, like Hyp mice, tibiae and calvariae in VDRf/f;DMP1Cre+ and NPT2aKO mice have enlarged osteocyte lacunae (tibiae: 0.15±0.02μm2(VDRf/f;DMP1Cre-) vs 0.19±0.02μm2(VDRf/f;DMP1Cre+), 0.12±0.02μm2(WT) vs 0.18±0.0μm2(NPT2aKO), calvariae: 0.09±0.02μm2(VDRf/f;DMP1Cre-) vs 0.11±0.02μm2(VDRf/f;DMP1Cre+), 0.08±0.02μm2(WT) vs 0.13±0.02μm2(NPT2aKO), p<0.05 all comparisons) and increased immunoreactivity of bone resorption marker Cathepsin K (Ctsk). The osteocyte enriched RNA isolated from tibiae in VDRf/f;DMP1Cre+ and NPT2aKO mice have enhanced expression of matrix resorption genes that are classically expressed by osteoclasts (Ctsk, Acp5, Atp6v0d2, Nhedc2). Treatment of Ocy454 osteocytes with 1,25D or phosphate inhibits the expression of these genes. Like Hyp mice, VDRf/f;DMP1Cre+ and NPT2aKO mice have impaired canalicular organization in tibia and calvaria. These studies demonstrate that hypophosphatemia and osteocyte-specific 1,25D actions regulate LCN remodeling. Impaired 1,25D action and low phosphate levels contribute to the abnormal LCN phenotype observed in XLH.
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Affiliation(s)
- Ye Yuan
- Harvard Medical School, Boston, Massachusetts, United States of America
- Division of Endocrinology, Diabetes, Hypertension, Brigham and Women’s Hospital, Boston, Massachusetts, United States of America
| | - Supriya Jagga
- Harvard Medical School, Boston, Massachusetts, United States of America
- Division of Endocrinology, Diabetes, Hypertension, Brigham and Women’s Hospital, Boston, Massachusetts, United States of America
| | - Janaina S. Martins
- Harvard Medical School, Boston, Massachusetts, United States of America
- Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Rakshya Rana
- Division of Endocrinology, Diabetes, Hypertension, Brigham and Women’s Hospital, Boston, Massachusetts, United States of America
| | - Paola Divieti Pajevic
- Department of Translational Dental Medicine, Boston University School of Dental Medicine, Boston, Massachusetts, United States of America
| | - Eva S. Liu
- Harvard Medical School, Boston, Massachusetts, United States of America
- Division of Endocrinology, Diabetes, Hypertension, Brigham and Women’s Hospital, Boston, Massachusetts, United States of America
- * E-mail:
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4
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Abstract
Our understanding of the regulation of phosphate balance has benefited tremendously from the molecular identification and characterization of genetic defects leading to a number of rare inherited or acquired disorders affecting phosphate homeostasis. The identification of the key phosphate-regulating hormone, fibroblast growth factor 23 (FGF23), as well as other molecules that control its production, such as the glycosyltransferase GALNT3, the endopeptidase PHEX, and the matrix protein DMP1, and molecules that function as downstream effectors of FGF23 such as the longevity factor Klotho and the phosphate transporters NPT2a and NPT2c, has permitted us to understand the complex interplay that exists between the kidneys, bone, parathyroid, and gut. Such insights from genetic disorders have allowed not only the design of potent targeted treatment of FGF23-dependent hypophosphatemic conditions, but also provide clinically relevant observations related to the dysregulation of mineral ion homeostasis in health and disease.
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Affiliation(s)
- Marta Christov
- Division of Nephrology, Department of Medicine, New York Medical College, Valhalla, NY, USA
| | - Harald Jüppner
- Endocrine Unit and Pediatric Nephrology Unit, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA.
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5
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Carrillo-López N, Panizo S, Alonso-Montes C, Martínez-Arias L, Avello N, Sosa P, Dusso AS, Cannata-Andía JB, Naves-Díaz M. High-serum phosphate and parathyroid hormone distinctly regulate bone loss and vascular calcification in experimental chronic kidney disease. Nephrol Dial Transplant 2018; 34:934-941. [DOI: 10.1093/ndt/gfy287] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Indexed: 12/15/2022] Open
Affiliation(s)
- Natalia Carrillo-López
- Bone and Mineral Research Unit, Hospital Universitario Central de Asturias, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), REDinREN-ISCIII, Oviedo, Spain
| | - Sara Panizo
- Bone and Mineral Research Unit, Hospital Universitario Central de Asturias, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), REDinREN-ISCIII, Oviedo, Spain
| | - Cristina Alonso-Montes
- Bone and Mineral Research Unit, Hospital Universitario Central de Asturias, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), REDinREN-ISCIII, Oviedo, Spain
| | - Laura Martínez-Arias
- Bone and Mineral Research Unit, Hospital Universitario Central de Asturias, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), REDinREN-ISCIII, Oviedo, Spain
| | - Noelia Avello
- Laboratorio de Medicina, Hospital Universitario Central de Asturias, Oviedo, Spain
| | - Patricia Sosa
- Departamento de Biología de Sistemas, Universidad de Alcalá, REDinREN-ISCIII, Alcalá de Henares, Spain
| | - Adriana S Dusso
- Bone and Mineral Research Unit, Hospital Universitario Central de Asturias, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), REDinREN-ISCIII, Oviedo, Spain
| | - Jorge B Cannata-Andía
- Bone and Mineral Research Unit, Hospital Universitario Central de Asturias, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), REDinREN-ISCIII, Oviedo, Spain
- Departamento de Medicina, Universidad de Oviedo, Oviedo, Spain
| | - Manuel Naves-Díaz
- Bone and Mineral Research Unit, Hospital Universitario Central de Asturias, Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), REDinREN-ISCIII, Oviedo, Spain
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6
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Kaneko I, Segawa H, Ikuta K, Hanazaki A, Fujii T, Tatsumi S, Kido S, Hasegawa T, Amizuka N, Saito H, Miyamoto KI. Eldecalcitol Causes FGF23 Resistance for Pi Reabsorption and Improves Rachitic Bone Phenotypes in the Male Hyp Mouse. Endocrinology 2018; 159:2741-2758. [PMID: 29878089 DOI: 10.1210/en.2018-00109] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 05/29/2018] [Indexed: 11/19/2022]
Abstract
X-linked hypophosphatemia (XLH), the most common form of inheritable rickets, is caused by inactivation of phosphate-regulating gene with homologies to endopeptidases on the X chromosome (PHEX) and leads to fibroblast growth factor (FGF) 23-dependent renal inorganic phosphate (Pi) wasting. In the present study, we investigated whether maintaining Pi homeostasis with a potent vitamin D3 analog, eldecalcitol [1α,25-dihydroxy-2β-(3-hydroxypropyloxy) vitamin D3; ED71], could improve hypophosphatemic rickets in a murine model of XLH, the Hyp mouse. Vehicle, ED71, or 1,25-dihydroxyvitamin D was subcutaneously injected five times weekly in wild-type (WT) and Hyp mice for 4 weeks, from 4 to 8 weeks of age. Injection of ED71 into WT mice suppressed the synthesis of renal 1,25-dihydroxyvitamin D and promoted phosphaturic activity. In contrast, administration of ED71 to Hyp mice completely restored renal Pi transport and NaPi-2a protein levels, although the plasma-intact FGF23 levels were further increased. In addition, ED71 markedly increased the levels of the scaffold proteins, renal sodium-hydrogen exchanger regulatory factor 1, and ezrin in the Hyp mouse kidney. Treatment with ED71 increased the body weight and improved hypophosphatemia, the bone volume/total volume, bone mineral content, and growth plate structure in Hyp mice. Thus, ED71 causes FGF23 resistance for phosphate reabsorption and improves rachitic bone phenotypes in Hyp mice. In conclusion, ED71 has opposite effects on phosphate homeostasis in WT and Hyp mice. Analysis of Hyp mice treated with ED71 could result in an additional model for elucidating PHEX abnormalities.
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Affiliation(s)
- Ichiro Kaneko
- Department of Molecular Nutrition, Tokushima University Graduate School of Biomedical Sciences, Tokushima, Japan
| | - Hiroko Segawa
- Department of Molecular Nutrition, Tokushima University Graduate School of Biomedical Sciences, Tokushima, Japan
| | - Kayo Ikuta
- Department of Molecular Nutrition, Tokushima University Graduate School of Biomedical Sciences, Tokushima, Japan
| | - Ai Hanazaki
- Department of Molecular Nutrition, Tokushima University Graduate School of Biomedical Sciences, Tokushima, Japan
| | - Toru Fujii
- Department of Molecular Nutrition, Tokushima University Graduate School of Biomedical Sciences, Tokushima, Japan
| | - Sawako Tatsumi
- Department of Molecular Nutrition, Tokushima University Graduate School of Biomedical Sciences, Tokushima, Japan
| | - Shinsuke Kido
- Department of Molecular Nutrition, Tokushima University Graduate School of Biomedical Sciences, Tokushima, Japan
| | - Tomoka Hasegawa
- Department of Developmental Biology of Hard Tissue, Graduate School of Dental Medicine, Hokkaido University, Sapporo, Japan
| | - Norio Amizuka
- Department of Developmental Biology of Hard Tissue, Graduate School of Dental Medicine, Hokkaido University, Sapporo, Japan
| | | | - Ken-Ichi Miyamoto
- Department of Molecular Nutrition, Tokushima University Graduate School of Biomedical Sciences, Tokushima, Japan
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7
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Nakamichi Y, Udagawa N, Suda T, Takahashi N. Mechanisms involved in bone resorption regulated by vitamin D. J Steroid Biochem Mol Biol 2018; 177:70-76. [PMID: 29146302 DOI: 10.1016/j.jsbmb.2017.11.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 10/26/2017] [Accepted: 11/12/2017] [Indexed: 12/31/2022]
Abstract
Active forms of vitamin D enhance osteoclastogenesis in vitro and in vivo through the vitamin D receptor (VDR) in osteoblast-lineage cells consisting of osteoblasts and osteocytes. This pro-resorptive activity was evident basically with higher concentrations of active vitamin D than those expected in physiological conditions. Nevertheless, vitamin D compounds have been used in Japan for treating osteoporosis to increase bone mineral density (BMD). Of note, the increase in BMD by long-term treatment with pharmacological (=near-physiological) doses of vitamin D compounds was caused by the suppression of bone resorption. Therefore, whether vitamin D expresses pro-resorptive or anti-resorptive properties seems to be dependent on the treatment protocols. We established osteoblast lineage-specific and osteoclast-specific VDR conditional knockout (cKO) mice using Osterix-Cre transgenic mice and Cathepsin K-Cre knock-in mice, respectively. According to our observation using these cKO mouse lines, neither VDR in osteoblast-lineage cells nor that in osteoclasts played important roles for osteoclastogenesis and bone resorption at homeostasis. However, using our cKO lines, we observed that VDR in osteoblast-lineage cells, but not osteoclasts, was involved in the anti-resorptive properties of pharmacological doses of vitamin D compounds in vivo. Two different osteoblast-lineage VDR cKO mouse lines were reported. One is a VDR cKO mouse line using alpha 1, type I collagen (Col1a1)-Cre transgenic mice (here we call Col1a1-VDR-cKO mice) and the other is that using dentin matrix protein 1 (Dmp1)-Cre transgenic mice (Dmp1-VDR-cKO mice). Col1a1-VDR-cKO mice exhibited slightly increased bone mass due to lowered bone resorption. In contrast, Dmp1-VDR-cKO mice exhibited no difference in BMD in agreement with our results regarding Ob-VDR-cKO mice. Here we discuss contradictory results and multiple modes of actions of vitamin D in bone resorption in detail. (279 words).
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Affiliation(s)
- Yuko Nakamichi
- Institute for Oral Science, Matsumoto Dental University, Shiojiri, Nagano 399-0781, Japan.
| | - Nobuyuki Udagawa
- Department of Biochemistry, Matsumoto Dental University, Shiojiri, Nagano 399-0781, Japan
| | - Tatsuo Suda
- Research Center for Genomic Medicine, Saitama Medical University, Saitama 350-1241, Japan
| | - Naoyuki Takahashi
- Institute for Oral Science, Matsumoto Dental University, Shiojiri, Nagano 399-0781, Japan
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8
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Abstract
Rickets is a bone disease associated with abnormal serum calcium and phosphate levels. The clinical presentation is heterogeneous and depends on the age of onset and pathogenesis but includes bowing deformities of the legs, short stature and widening of joints. The disorder can be caused by nutritional deficiencies or genetic defects. Mutations in genes encoding proteins involved in vitamin D metabolism or action, fibroblast growth factor 23 (FGF23) production or degradation, renal phosphate handling or bone mineralization have been identified. The prevalence of nutritional rickets has substantially declined compared with the prevalence 200 years ago, but the condition has been re-emerging even in some well-resourced countries; prematurely born infants or breastfed infants who have dark skin types are particularly at risk. Diagnosis is usually established by medical history, physical examination, biochemical tests and radiography. Prevention is possible only for nutritional rickets and includes supplementation or food fortification with calcium and vitamin D either alone or in combination with sunlight exposure. Treatment of typical nutritional rickets includes calcium and/or vitamin D supplementation, although instances infrequently occur in which phosphate repletion may be necessary. Management of heritable types of rickets associated with defects in vitamin D metabolism or activation involves the administration of vitamin D metabolites. Oral phosphate supplementation is usually indicated for FGF23-independent phosphopenic rickets, whereas the conventional treatment of FGF23-dependent types of rickets includes a combination of phosphate and activated vitamin D; an anti-FGF23 antibody has shown promising results and is under further study.
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9
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Nakamichi Y, Udagawa N, Horibe K, Mizoguchi T, Yamamoto Y, Nakamura T, Hosoya A, Kato S, Suda T, Takahashi N. VDR in Osteoblast-Lineage Cells Primarily Mediates Vitamin D Treatment-Induced Increase in Bone Mass by Suppressing Bone Resorption. J Bone Miner Res 2017; 32:1297-1308. [PMID: 28177161 DOI: 10.1002/jbmr.3096] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 02/01/2017] [Accepted: 02/03/2017] [Indexed: 01/01/2023]
Abstract
Long-term treatment with active vitamin D [1α,25(OH)2 D3 ] and its derivatives is effective for increasing bone mass in patients with primary and secondary osteoporosis. Derivatives of 1α,25(OH)2 D3 , including eldecalcitol (ELD), exert their actions through the vitamin D receptor (VDR). ELD is more resistant to metabolic degradation than 1α,25(OH)2 D3 . It is reported that ELD treatment causes a net increase in bone mass by suppressing bone resorption rather than by increasing bone formation in animals and humans. VDR in bone and extraskeletal tissues regulates bone mass and secretion of osteotropic hormones. Therefore, it is unclear what types of cells expressing VDR preferentially regulate the vitamin D-induced increase in bone mass. Here, we examined the effects of 4-week treatment with ELD (50 ng/kg/day) on bone using osteoblast lineage-specific VDR conditional knockout (Ob-VDR-cKO) and osteoclast-specific VDR cKO (Ocl-VDR-cKO) male mice aged 10 weeks. Immunohistochemically, VDR in bone was detected preferentially in osteoblasts and osteocytes. Ob-VDR-cKO mice showed normal bone phenotypes, despite no appreciable immunostaining of VDR in bone. Ob-VDR-cKO mice failed to increase bone mass in response to ELD treatment. Ocl-VDR-cKO mice also exhibited normal bone phenotypes, but normally responded to ELD. ELD-induced FGF23 production in bone was regulated by VDR in osteoblast-lineage cells. These findings suggest that the vitamin D treatment-induced increase in bone mass is mediated by suppressing bone resorption through VDR in osteoblast-lineage cells. © 2017 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.
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Affiliation(s)
- Yuko Nakamichi
- Institute for Oral Science, Matsumoto Dental University, Nagano, Japan
| | - Nobuyuki Udagawa
- Department of Biochemistry, Matsumoto Dental University, Nagano, Japan
| | - Kanji Horibe
- Department of Oral Histology, Matsumoto Dental University, Nagano, Japan
| | | | - Yoko Yamamoto
- Department of Surgical Oncology, The University of Tokyo, Tokyo, Japan
| | - Takashi Nakamura
- Department of Biochemistry & Integrative Medical Biology, School of Medicine, Keio University, Tokyo, Japan
| | - Akihiro Hosoya
- Department of Oral Histology, Matsumoto Dental University, Nagano, Japan
| | - Shigeaki Kato
- Jyoban Hospital, Tokiwa Foundation, Fukushima, Japan
| | - Tatsuo Suda
- Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Naoyuki Takahashi
- Institute for Oral Science, Matsumoto Dental University, Nagano, Japan
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10
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Ko FC, Martins JS, Reddy P, Bragdon B, Hussein AI, Gerstenfeld LC, Demay MB. Acute Phosphate Restriction Impairs Bone Formation and Increases Marrow Adipose Tissue in Growing Mice. J Bone Miner Res 2016; 31:2204-2214. [PMID: 27324177 DOI: 10.1002/jbmr.2891] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 06/06/2016] [Accepted: 06/13/2016] [Indexed: 01/28/2023]
Abstract
Phosphate plays a critical role in chondrocyte maturation and skeletal mineralization. Studies examining the consequences of dietary phosphate restriction in growing mice demonstrated not only the development of rickets, but also a dramatic decrease in bone accompanied by increased marrow adipose tissue (MAT). Thus studies were undertaken to determine the effects of dietary phosphate restriction on bone formation and bone marrow stromal cell (BMSC) differentiation. Acute phosphate restriction of 28-day-old mice profoundly inhibited bone formation within 48 hours. It also resulted in increased mRNA expression of the early osteolineage markers Sox9 and Runt-related transcription factor 2 (Runx2), accompanied by decreased expression of the late osteolineage markers Osterix and Osteocalcin in BMSCs and osteoblasts, suggesting that phosphate restriction arrests osteoblast differentiation between Runx2 and Osterix. Increased expression of PPARγ and CEBPα, key regulators of adipogenic differentiation, was observed within 1 week of dietary phosphate restriction and was followed by a 13-fold increase in MAT at 3 weeks of phosphate restriction. In vitro phosphate restriction did not alter BMSC osteogenic or adipogenic colony formation, implicating aberrant paracrine or endocrine signaling in the in vivo phenotype. Because BMP signaling regulates the transition between Runx2 and Osterix, this pathway was interrogated. A dramatic decrease in pSmad1/5/9 immunoreactivity was observed in the osteoblasts of phosphate-restricted mice on day 31 (d31) and d35. This was accompanied by attenuated expression of the BMP target genes Id1, KLF10, and Foxc2, the latter of which promotes osteogenic and angiogenic differentiation while impairing adipogenesis. A decrease in expression of the Notch target gene Hey1, a BMP-regulated gene that governs angiogenesis, was also observed in phosphate-restricted mice, in association with decreased metaphyseal marrow vasculature. Whereas circulating phosphate levels are known to control growth plate maturation and skeletal mineralization, these studies reveal novel consequences of phosphate restriction in the regulation of bone formation and osteoblast differentiation. © 2016 American Society for Bone and Mineral Research.
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Affiliation(s)
- Frank C Ko
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA
| | - Janaina S Martins
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA
| | - Pooja Reddy
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA
| | - Beth Bragdon
- Department of Orthopaedic Surgery, Boston University School of Medicine, Boston, MA, USA
| | - Amira I Hussein
- Department of Orthopaedic Surgery, Boston University School of Medicine, Boston, MA, USA
| | - Louis C Gerstenfeld
- Department of Orthopaedic Surgery, Boston University School of Medicine, Boston, MA, USA
| | - Marie B Demay
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA
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11
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Liu ES, Martins JS, Raimann A, Chae BT, Brooks DJ, Jorgetti V, Bouxsein ML, Demay MB. 1,25-Dihydroxyvitamin D Alone Improves Skeletal Growth, Microarchitecture, and Strength in a Murine Model of XLH, Despite Enhanced FGF23 Expression. J Bone Miner Res 2016; 31:929-39. [PMID: 26751835 PMCID: PMC4862933 DOI: 10.1002/jbmr.2783] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 01/05/2016] [Accepted: 01/07/2016] [Indexed: 01/24/2023]
Abstract
X-linked hypophosphatemia (XLH) is characterized by impaired renal tubular reabsorption of phosphate owing to increased circulating FGF23 levels, resulting in rickets in growing children and impaired bone mineralization. Increased FGF23 decreases renal brush border membrane sodium-dependent phosphate transporter IIa (Npt2a) causing renal phosphate wasting, impairs 1-α hydroxylation of 25-hydroxyvitamin D, and induces the vitamin D 24-hydroxylase, leading to inappropriately low circulating levels of 1,25-dihydroxyvitamin D (1,25D). The goal of therapy is prevention of rickets and improvement of growth in children by phosphate and 1,25D supplementation. However, this therapy is often complicated by hypercalcemia and nephrocalcinosis and does not always prevent hyperparathyroidism. To determine if 1,25D or blocking FGF23 action can improve the skeletal phenotype without phosphate supplementation, mice with XLH (Hyp) were treated with daily 1,25D repletion, FGF23 antibodies (FGF23Ab), or biweekly high-dose 1,25D from d2 to d75 without supplemental phosphate. All treatments maintained normocalcemia, increased serum phosphate, and normalized parathyroid hormone levels. They also prevented the loss of Npt2a, α-Klotho, and pERK1/2 immunoreactivity observed in the kidneys of untreated Hyp mice. Daily treatment with 1,25D decreased urine phosphate losses despite a marked increase in bone FGF23 mRNA and in circulating FGF23 levels. Daily 1,25D was more effective than other treatments in normalizing the growth plate and metaphyseal organization. In addition to being the only therapy that normalized lumbar vertebral height and body weight, daily 1,25D therapy normalized bone geometry and was more effective than FGF23Ab in improving trabecular bone structure. Daily 1,25D and FGF23Ab improved cortical microarchitecture and whole-bone biomechanical properties more so than biweekly 1,25D. Thus, monotherapy with 1,25D improves growth, skeletal microarchitecture, and bone strength in the absence of phosphate supplementation despite enhancing FGF23 expression, demonstrating that 1,25D has direct beneficial effects on the skeleton in XLH, independent of its role in phosphate homeostasis. © 2016 American Society for Bone and Mineral Research.
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Affiliation(s)
- Eva S Liu
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women's Hospital, Boston, MA, USA.,Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA
| | - Janaina S Martins
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA.,Division of Nephrology, Universidade de São Paulo, São Paulo, Brazil
| | - Adalbert Raimann
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA.,Department of Pediatrics and Adolescent Medicine, Medical University Vienna, Vienna, Austria
| | | | - Daniel J Brooks
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Department of Orthopedics, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Vanda Jorgetti
- Division of Nephrology, Universidade de São Paulo, São Paulo, Brazil
| | - Mary L Bouxsein
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA.,Department of Orthopedics, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Marie B Demay
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA
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12
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Abstract
The vitamin D endocrine system regulates a broad variety of independent biological processes, and its deficiency is associated with rickets, bone diseases, diabetes, cardiovascular diseases, and tuberculosis. Cellular and molecular studies have also shown that it is implicated in the suppression of cancer cell invasion, angiogenesis, and metastasis. Sunlight exposure and consequent increased circulating levels of vitamin D are associated with reduced occurrence and a reduced mortality in different histological types of cancer, including those resident in the skin, prostate, breast, colon, ovary, kidney, and bladder. The vitamin D receptor (VDR) as a steroid hormone superfamily of nuclear receptors is highly expressed in epithelial cells at risk for carcinogenesis, providing a direct molecular link by which vitamin D status impacts on carcinogenesis. Because VDR expression is retained in many human tumors, vitamin D status may be an important modulator of cancer progression in persons living with cancer. The aim of this review is to highlight the relationship between vitamin D, VDR, and cancer, summarizing several mechanisms proposed to explain the potential protective effect of vitamin D against the development and progression of cancer.
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Affiliation(s)
- Xiayu Wu
- School of Life Sciences, The Engineering Research Center of Sustainable Development and Utilization of Biomass Energy, Ministry of Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Tao Zhou
- School of Life Sciences, The Engineering Research Center of Sustainable Development and Utilization of Biomass Energy, Ministry of Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Neng Cao
- School of Life Sciences, The Engineering Research Center of Sustainable Development and Utilization of Biomass Energy, Ministry of Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Juan Ni
- School of Life Sciences, The Engineering Research Center of Sustainable Development and Utilization of Biomass Energy, Ministry of Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Xu Wang
- School of Life Sciences, The Engineering Research Center of Sustainable Development and Utilization of Biomass Energy, Ministry of Education, Yunnan Normal University, Kunming, Yunnan, China
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13
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Abstract
Over the last decade the discovery of fibroblast growth factor 23 (FGF23) and the progressive and ongoing clarification of its role in phosphate and mineral metabolism have led to expansion of the diagnostic spectrum of primary hypophosphatemic syndromes. This article focuses on the impairment of growth in these syndromes. Growth retardation is a common, but not constant, feature and it presents with large variability. As a result of the very low prevalence of other forms of primary hypophosphatemic syndromes, the description of longitudinal growth and the pathogenesis of its impairment have been mostly studied in X-linked hypophosphatemia (XLH) patients and in Hyp mice, the animal model of this disease. In general, children with XLH have short stature with greater shortness of lower limbs than trunk. Treatment with phosphate supplements and 1α vitamin D derivatives heals active lesions of rickets, but does not normalize growth of XLH patients. Patients might benefit from recombinant human growth hormone (rhGH) therapy, which may accelerate the growth rate without increasing body disproportion or correcting hypophosphatemia. These clinical data as well as research findings obtained in Hyp mice suggest that the pathogenesis of defective growth in XLH and other hypophosphatemic syndromes is not entirely dependent on the mineralization disorder and point to other effects of hypophosphatemia itself or FGF23 on the metabolism of bone and growth plate.
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Affiliation(s)
- Fernando Santos
- Hospital Universitario Central de Asturias & University of Oviedo, Oviedo, Asturias, Spain.
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14
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Saini RK, Kaneko I, Jurutka PW, Forster R, Hsieh A, Hsieh JC, Haussler MR, Whitfield GK. 1,25-dihydroxyvitamin D(3) regulation of fibroblast growth factor-23 expression in bone cells: evidence for primary and secondary mechanisms modulated by leptin and interleukin-6. Calcif Tissue Int 2013; 92:339-53. [PMID: 23263654 PMCID: PMC3595337 DOI: 10.1007/s00223-012-9683-5] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Accepted: 11/30/2012] [Indexed: 12/21/2022]
Abstract
Fibroblast growth factor-23 (FGF23) is a circulating hormone that acts to correct hyperphosphatemic states by inhibiting renal phosphate reabsorption and to prevent hypervitaminosis D by feedback repressing 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) biosynthesis. FGF23 gene expression in the osteoblast/osteocyte is induced by the nuclear vitamin D receptor (VDR) bound to 1,25(OH)2D3, but cycloheximide sensitivity of this induction suggests that it may occur largely via secondary mechanisms requiring cooperating transcription factors. We therefore sought to identify 1,25(OH)2D3-regulated transcription factors that might impact FGF23 expression. Although neither leptin nor interleukin-6 (IL-6) alone affects FGF23 expression, leptin treatment was found to potentiate 1,25(OH)2D3 upregulation of FGF23 in UMR-106 cells, whereas IL-6 treatment blunted this upregulation. Genomic analyses revealed conserved binding sites for STATs (signal transduction mediators of leptin and IL-6 action) along with transcription factor ETS1 in human and other mammalian FGF23 genes. Further, STAT3, STAT1, ETS1, and VDR mRNAs were induced in a dose-dependent manner by 1,25(OH)2D3 in UMR-106 cells. Bioinformatic analysis identified nine potential VDREs in a genomic interval containing human FGF23. Six of the putative VDREs were capable of mediating direct transcriptional activation of a heterologous reporter gene when bound by a 1,25(OH)2D3-liganded VDR complex. A model is proposed wherein 1,25(OH)2D3 upregulates FGF23 production directly via multiple VDREs and indirectly via induction of STAT3, ETS1, and VDR transcription factors that are then activated via cell surface and intracellular signaling to cooperate in the induction of FGF23 through DNA looping and generation of euchromatin architecture.
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Affiliation(s)
- Rimpi K. Saini
- School of Mathematical and Natural Sciences, Arizona State, University, Phoenix, AZ 85306, USA
| | - Ichiro Kaneko
- School of Mathematical and Natural Sciences, Arizona State, University, Phoenix, AZ 85306, USA
| | - Peter W. Jurutka
- School of Mathematical and Natural Sciences, Arizona State, University, Phoenix, AZ 85306, USA. Department of Basic Medical Sciences, University of Arizona College of Medicine, Phoenix, AZ 85004, USA
| | - Ryan Forster
- Department of Basic Medical Sciences, University of Arizona College of Medicine, Phoenix, AZ 85004, USA
| | - Antony Hsieh
- Department of Basic Medical Sciences, University of Arizona College of Medicine, Phoenix, AZ 85004, USA
| | - Jui-Cheng Hsieh
- Department of Basic Medical Sciences, University of Arizona College of Medicine, Phoenix, AZ 85004, USA
| | - Mark R. Haussler
- Department of Basic Medical Sciences, University of Arizona College of Medicine, Phoenix, AZ 85004, USA
| | - G. Kerr Whitfield
- Department of Basic Medical Sciences, University of Arizona College of Medicine, Phoenix, AZ 85004, USA
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15
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Wöhrle S, Henninger C, Bonny O, Thuery A, Beluch N, Hynes NE, Guagnano V, Sellers WR, Hofmann F, Kneissel M, Graus Porta D. Pharmacological inhibition of fibroblast growth factor (FGF) receptor signaling ameliorates FGF23-mediated hypophosphatemic rickets. J Bone Miner Res 2013; 28:899-911. [PMID: 23129509 DOI: 10.1002/jbmr.1810] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 10/18/2012] [Accepted: 10/23/2012] [Indexed: 12/11/2022]
Abstract
Fibroblast growth factor 23 (FGF23) is a circulating factor secreted by osteocytes that is essential for phosphate homeostasis. In kidney proximal tubular cells FGF23 inhibits phosphate reabsorption and leads to decreased synthesis and enhanced catabolism of 1,25-dihydroxyvitamin D3 (1,25[OH]2 D3 ). Excess levels of FGF23 cause renal phosphate wasting and suppression of circulating 1,25(OH)2 D3 levels and are associated with several hereditary hypophosphatemic disorders with skeletal abnormalities, including X-linked hypophosphatemic rickets (XLH) and autosomal recessive hypophosphatemic rickets (ARHR). Currently, therapeutic approaches to these diseases are limited to treatment with activated vitamin D analogues and phosphate supplementation, often merely resulting in partial correction of the skeletal aberrations. In this study, we evaluate the use of FGFR inhibitors for the treatment of FGF23-mediated hypophosphatemic disorders using NVP-BGJ398, a novel selective, pan-specific FGFR inhibitor currently in Phase I clinical trials for cancer therapy. In two different hypophosphatemic mouse models, Hyp and Dmp1-null mice, resembling the human diseases XLH and ARHR, we find that pharmacological inhibition of FGFRs efficiently abrogates aberrant FGF23 signaling and normalizes the hypophosphatemic and hypocalcemic conditions of these mice. Correspondingly, long-term FGFR inhibition in Hyp mice leads to enhanced bone growth, increased mineralization, and reorganization of the disturbed growth plate structure. We therefore propose NVP-BGJ398 treatment as a novel approach for the therapy of FGF23-mediated hypophosphatemic diseases.
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Affiliation(s)
- Simon Wöhrle
- Novartis Institutes for BioMedical Research, Basel, Switzerland
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16
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Demay MB. Physiological insights from the vitamin D receptor knockout mouse. Calcif Tissue Int 2013; 92:99-105. [PMID: 22903507 PMCID: PMC3511627 DOI: 10.1007/s00223-012-9633-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Accepted: 07/16/2012] [Indexed: 12/14/2022]
Abstract
Identification of vitamin D as a potent antirachitic factor almost a century ago prompted investigations aimed at addressing its mechanism of action and key target tissues. Studies in vitamin D deficiency models and in kindreds with impaired hormone activation and function were critical in identifying key steps in the vitamin D signaling pathway. Studies in humans with vitamin D receptor (VDR) mutations provided a tremendous amount of information regarding the role of this receptor in calcium and skeletal homeostasis. The availability of mouse models of VDR ablation provided an important tool for detailed molecular analyses of the pathophysiologic basis for the skeletal, parathyroid and cutaneous phenotypes observed in mice and humans with impaired VDR function. These investigations revealed that a critical action of the liganded receptor is the promotion of intestinal calcium absorption. Bypassing this defect by dietary or transgenic rescue prevents the severe skeletal phenotype of the VDR ablated mice, as well as the development of hyperparathyroidism. In contrast, intestine specific ablation of the receptor results in marked skeletal pathology. Like their human counterparts, VDR knockout mice develop alopecia. Studies in these mice demonstrated that the actions of the VDR required for cyclical regeneration of the hair follicle and prevention of alopecia were shown independent of 1,25-dihydroxyvitamin D demonstrating that the unliganded receptor has an important role in the cutaneous homeostasis.
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Affiliation(s)
- Marie B Demay
- Endocrine Unit, Massachusetts General Hospital, Harvard Medical School, Thier 11, 50 Blossom St., Boston, MA, USA.
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17
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Wang B, Yang Y, Liu L, Blair HC, Friedman PA. NHERF1 regulation of PTH-dependent bimodal Pi transport in osteoblasts. Bone 2013; 52:268-77. [PMID: 23046970 PMCID: PMC3513631 DOI: 10.1016/j.bone.2012.10.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 09/18/2012] [Accepted: 10/01/2012] [Indexed: 02/01/2023]
Abstract
Control of systemic inorganic phosphate (Pi) levels is crucial for osteoid mineralization. Parathyroid hormone (PTH) mediates actions on phosphate homeostasis mostly by regulating the activity of the type 2 sodium-phosphate cotransporter (Npt2), and this action requires the PDZ protein NHERF1. Osteoblasts express Npt2 and in response to PTH enhance osteogenesis by increasing mineralized matrix. The regulation of Pi transport in osteoblasts is poorly understood. To address this gap we characterized PTH-dependent Pi transport and the role of NHERF1 in primary mouse calvarial osteoblasts. Under proliferating conditions osteoblasts express Npt2a, Npt2b, PTH receptor, and NHERF1. Npt2a mRNA expression was lower in calvarial osteoblasts from NHERF1-null mice. Under basal conditions Pi uptake in osteoblasts from wild-type mice was greater than that of knockout mice. PTH inhibited Pi uptake in proliferating osteoblasts from wild-type mice, but not in cells from knockout mice. In vitro induction of mineralization enhanced osteoblast differentiation and increased osterix and osteocalcin expression. Contrary to the results with proliferating osteoblasts, PTH increased Pi uptake and ATP secretion in differentiated osteoblasts from wild-type mice. PTH had no effect on Pi uptake or ATP release in differentiated osteoblasts from knockout mice. NHERF1 regulation of PTH-sensitive Pi uptake in proliferating osteoblasts is mediated by cAMP/PKA and PLC/PKC, while modulation of Pi uptake in differentiated osteoblasts depends only on cAMP/PKA signaling. The results suggest that NHERF1 cooperates with PTH in differentiated osteoblasts to increase matrix mineralization. We conclude that NHERF1 regulates PTH that differentially affects Na-dependent Pi transport at distinct stages of osteoblast proliferation and maturation.
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Affiliation(s)
- Bin Wang
- Laboratory for G Protein-Coupled Receptor Biology, Department of Pharmacology & Chemical Biology, Pittsburgh, PA, USA
| | - Yanmei Yang
- Laboratory for G Protein-Coupled Receptor Biology, Department of Pharmacology & Chemical Biology, Pittsburgh, PA, USA
| | - Li Liu
- Pittsburgh Veterans Affairs Medical Center and Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Harry C. Blair
- Pittsburgh Veterans Affairs Medical Center and Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Peter A. Friedman
- Laboratory for G Protein-Coupled Receptor Biology, Department of Pharmacology & Chemical Biology, Pittsburgh, PA, USA
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18
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Gattineni J, Baum M. Genetic disorders of phosphate regulation. Pediatr Nephrol 2012; 27:1477-87. [PMID: 22350303 PMCID: PMC3407352 DOI: 10.1007/s00467-012-2103-2] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Revised: 12/08/2011] [Accepted: 12/09/2011] [Indexed: 12/21/2022]
Abstract
Regulation of phosphate homeostasis is critical for many biological processes, and both hypophosphatemia and hyperphosphatemia can have adverse clinical consequences. Only a very small percentage (1%) of total body phosphate is present in the extracellular fluid, which is measured by routine laboratory assays and does not reflect total body phosphate stores. Phosphate is absorbed from the gastrointestinal tract via the transcellular route [sodium phosphate cotransporter 2b (NaPi2b)] and across the paracellular pathway. Approximately 85% of the filtered phosphate is reabsorbed from the kidney, predominantly in the proximal tubule, by NaPi2a and NaPi2c, which are present on the brush border membrane. Renal phosphate transport is tightly regulated. Dietary phosphate intake, parathyroid hormone (PTH), 1,25 (OH)2 vitamin D3, and fibroblast growth factor 23 (FGF23) are the principal regulators of phosphate reabsorption from the kidney. Recent advances in genetic techniques and animal models have identified many genetic disorders of phosphate homeostasis. Mutations in NaPi2a and NaPi2c; and hormonal dysregulation of PTH, FGF23, and Klotho, are primarily responsible for most genetic disorders of phosphate transport. The main focus of this educational review article is to discuss the genetic and clinical features of phosphate regulation disorders and provide understanding and treatment options.
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Affiliation(s)
- Jyothsna Gattineni
- Department of Pediatrics, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75235-9063, USA.
| | - Michel Baum
- Department of Pediatrics, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75235-9063 USA ,Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75235-9063 USA
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19
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Haussler MR, Whitfield GK, Kaneko I, Forster R, Saini R, Hsieh JC, Haussler CA, Jurutka PW. The role of vitamin D in the FGF23, klotho, and phosphate bone-kidney endocrine axis. Rev Endocr Metab Disord 2012; 13:57-69. [PMID: 21932165 PMCID: PMC3288475 DOI: 10.1007/s11154-011-9199-8] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
1,25-dihydroxyvitamin D (1,25D), through association with the nuclear vitamin D receptor (VDR), exerts control over a novel endocrine axis consisting of the bone-derived hormone FGF23, and the kidney-expressed klotho, CYP27B1, and CYP24A1 genes, which together prevent hyperphosphatemia/ectopic calcification and govern the levels of 1,25D to maintain bone mineral integrity while promoting optimal function of other vital tissues. When occupied by 1,25D, VDR interacts with RXR to form a heterodimer that binds to VDREs in the region of genes directly controlled by 1,25D (e.g., FGF23, klotho, Npt2c, CYP27B1 and CYP24A1). By recruiting complexes of comodulators, activated VDR initiates a series of events that induces or represses the transcription of genes encoding proteins such as: the osteocyte-derived hormone, FGF23; the renal anti-senescence factor and protein co-receptor for FGF23, klotho; other mediators of phosphate transport including Npt2a/c; and vitamin D hormone metabolic enzymes, CYP27B1 and CYP24A1. The mechanism whereby osteocytes are triggered to release FGF23 is yet to be fully defined, but 1,25D, phosphate, and leptin appear to play major roles. The kidney responds to FGF23 to elicit CYP24A1-catalyzed detoxification of the 1,25D hormone while also repressing both Npt2a/c to mediate phosphate elimination and CYP27B1 to limit de novo 1,25D synthesis. Comprehension of these skeletal and renal actions of 1,25D should facilitate the development of novel mimetics to prevent ectopic calcification, chronic renal and vascular disease, and promote healthful aging.
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Affiliation(s)
- Mark R Haussler
- Department of Basic Medical Sciences, University of Arizona College of Medicine-Phoenix, Phoenix, AZ 85004, USA.
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20
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Stubbs JR, He N, Idiculla A, Gillihan R, Liu S, David V, Hong Y, Quarles LD. Longitudinal evaluation of FGF23 changes and mineral metabolism abnormalities in a mouse model of chronic kidney disease. J Bone Miner Res 2012; 27:38-46. [PMID: 22031097 PMCID: PMC3439562 DOI: 10.1002/jbmr.516] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Revised: 08/23/2011] [Accepted: 09/07/2011] [Indexed: 12/11/2022]
Abstract
Fibroblast growth factor 23 (FGF23) is a phosphaturic and vitamin D-regulatory hormone of putative bone origin that is elevated in patients with chronic kidney disease (CKD). The mechanisms responsible for elevations of FGF23 and its role in the pathogenesis of chronic kidney disease-mineral bone disorder (CKD-MBD) remain uncertain. We investigated the association between FGF23 serum levels and kidney disease progression, as well as the phenotypic features of CKD-MBD in a Col4a3 null mouse model of human autosomal-recessive Alport syndrome. These mice exhibited progressive renal failure, declining 1,25(OH)(2)D levels, increments in parathyroid hormone (PTH) and FGF23, late-onset hypocalcemia and hyperphosphatemia, high-turnover bone disease, and increased mortality. Serum levels of FGF23 increased in the earliest stages of renal damage, before elevations in blood urea nitrogen (BUN) and creatinine. FGF23 gene transcription in bone, however, did not increase until late-stage kidney disease, when serum FGF23 levels were exponentially elevated. Further evaluation of bone revealed trabecular osteocytes to be the primary cell source for FGF23 production in late-stage disease. Changes in FGF23 mirrored the rise in serum PTH and the decline in circulating 1,25(OH)(2)D. The rise in PTH and FGF23 in Col4a3 null mice coincided with an increase in the urinary fractional excretion of phosphorus and a progressive decline in sodium-phosphate cotransporter gene expression in the kidney. Our findings suggest elevations of FGF23 in CKD to be an early marker of renal injury that increases before BUN and serum creatinine. An increased production of FGF23 by bone may not be responsible for early increments in FGF23 in CKD but does appear to contribute to FGF23 levels in late-stage disease. Elevations in FGF23 and PTH coincide with an increase in urinary phosphate excretion that likely prevents the early onset of hyperphosphatemia in the face of increased bone turnover and a progressive decline in functional renal mass.
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Affiliation(s)
- Jason R Stubbs
- The Kidney Institute, University of Kansas Medical Center, Kansas City, KS 66160, USA.
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21
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Khosla S, Bellido TM, Drezner MK, Gordon CM, Harris TB, Kiel DP, Kream BE, LeBoff MS, Lian JB, Peterson CA, Rosen CJ, Williams JP, Winer KK, Sherman SS. Forum on aging and skeletal health: summary of the proceedings of an ASBMR workshop. J Bone Miner Res 2011; 26:2565-78. [PMID: 21915901 PMCID: PMC3625440 DOI: 10.1002/jbmr.488] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Accepted: 07/14/2011] [Indexed: 11/06/2022]
Abstract
With the aging of the population, the scope of the problem of age-related bone loss and osteoporosis will continue to increase. As such, it is critical to obtain a better understanding of the factors determining the acquisition and loss of bone mass from childhood to senescence. While there have been significant advances in recent years in our understanding of both the basic biology of aging and a clinical definition of age-related frailty, few of these concepts in aging research have been evaluated adequately for their relevance and application to skeletal aging or fracture prevention. The March 2011 Forum on Aging and Skeletal Health, sponsored by the NIH and ASBMR, sought to bring together leaders in aging and bone research to enhance communications among diverse fields of study so as to accelerate the pace of scientific advances needed to reduce the burden of osteoporotic fractures. This report summarizes the major concepts presented at that meeting and in each area identifies key questions to help set the agenda for future research in skeletal aging.
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Affiliation(s)
- Sundeep Khosla
- College of Medicine, Mayo Clinic, Rochester, MN 55905, USA.
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22
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Ardura JA, Friedman PA. Regulation of G protein-coupled receptor function by Na+/H+ exchange regulatory factors. Pharmacol Rev 2011; 63:882-900. [PMID: 21873413 DOI: 10.1124/pr.110.004176] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Many G protein-coupled receptors (GPCR) exert patterns of cell-specific signaling and function. Mounting evidence now supports the view that cytoplasmic adapter proteins contribute critically to this behavior. Adapter proteins recognize highly conserved motifs such as those for Src homology 3 (SH3), phosphotyrosine-binding (PTB), and postsynaptic density 95/discs-large/zona occludens (PDZ) docking sequences in candidate GPCRs. Here we review the behavior of the Na+/H+ exchange regulatory factor (NHERF) family of PDZ adapter proteins on GPCR signalling, trafficking, and function. Structural determinants of NHERF proteins that allow them to recognize targeted GPCRs are considered. NHERF1 and NHERF2 are capable also of modifying the assembled complex of accessory proteins such as β-arrestins, which have been implicated in regulating GPCR signaling. In addition, NHERF1 and NHERF2 modulate GPCR signaling by altering the G protein to which the receptor binds or affect other regulatory proteins that affect GTPase activity, protein kinase A, phospholipase C, or modify downstream signaling events. Small molecules targeting the site of NHERF1-GPCR interaction are being developed and may become important and selective drug candidates.
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Affiliation(s)
- Juan A Ardura
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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23
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Lieben L, Carmeliet G, Masuyama R. Calcemic actions of vitamin D: effects on the intestine, kidney and bone. Best Pract Res Clin Endocrinol Metab 2011; 25:561-72. [PMID: 21872798 DOI: 10.1016/j.beem.2011.05.008] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The analysis of mice that lack systemically the actions of the active form of vitamin D, 1,25(OH)₂D, has shown that 1,25(OH)₂D is an essential regulator of calcium homeostasis and that its actions are aimed at maintaining serum calcium levels within narrow limits. Especially the stimulation of intestinal calcium transport by 1,25(OH)₂D is important for calcium and bone homeostasis. The involved transporters are however still elusive. The targeted deletion of 1,25(OH)₂D action in chondrocytes has provided compelling evidence for a paracrine control of bone development and endocrine regulation of phosphate homeostasis by 1,25(OH)₂D. Targeting vitamin D receptor (VDR) function in other tissues will further enhance our understanding of the cell-type specific action of 1,25(OH)₂D. In this review, we will discuss the current understanding and remaining questions concerning the calcemic actions of 1,25(OH)₂D in the intestine, kidney and bone, with special focus on the evidence obtained by the use of transgenic mouse models.
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Affiliation(s)
- Liesbet Lieben
- Laboratory of Experimental Medicine & Endocrinology, Katholieke Universiteit Leuven, Herestraat 49, Leuven, Belgium.
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24
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Bockman RS. First it's rickets, then it's not the sodium-phosphate transporter 2a knockout mystery. Endocrinology 2010; 151:4599-601. [PMID: 20858767 DOI: 10.1210/en.2010-0818] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Richard S Bockman
- Division of Endocrinology, Weill Cornell Medical College of Cornell University and Hospital for Special Surgery, 535 East 70th Street, New York, New York 10021, USA.
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