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Tian L, Andrews C, Yan Q, Yang JJ. Molecular regulation of calcium-sensing receptor (CaSR)-mediated signaling. Chronic Dis Transl Med 2024; 10:167-194. [PMID: 39027195 PMCID: PMC11252437 DOI: 10.1002/cdt3.123] [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: 03/04/2024] [Revised: 03/29/2024] [Accepted: 04/09/2024] [Indexed: 07/20/2024] Open
Abstract
Calcium-sensing receptor (CaSR), a family C G-protein-coupled receptor, plays a crucial role in regulating calcium homeostasis by sensing small concentration changes of extracellular Ca2+, Mg2+, amino acids (e.g., L-Trp and L-Phe), small peptides, anions (e.g., HCO3 - and PO4 3-), and pH. CaSR-mediated intracellular Ca2+ signaling regulates a diverse set of cellular processes including gene transcription, cell proliferation, differentiation, apoptosis, muscle contraction, and neuronal transmission. Dysfunction of CaSR with mutations results in diseases such as autosomal dominant hypocalcemia, familial hypocalciuric hypercalcemia, and neonatal severe hyperparathyroidism. CaSR also influences calciotropic disorders, such as osteoporosis, and noncalciotropic disorders, such as cancer, Alzheimer's disease, and pulmonary arterial hypertension. This study first reviews recent advances in biochemical and structural determination of the framework of CaSR and its interaction sites with natural ligands, as well as exogenous positive allosteric modulators and negative allosteric modulators. The establishment of the first CaSR protein-protein interactome network revealed 94 novel players involved in protein processing in endoplasmic reticulum, trafficking, cell surface expression, endocytosis, degradation, and signaling pathways. The roles of these proteins in Ca2+-dependent cellular physiological processes and in CaSR-dependent cellular signaling provide new insights into the molecular basis of diseases caused by CaSR mutations and dysregulated CaSR activity caused by its protein interactors and facilitate the design of therapeutic agents that target CaSR and other family C G-protein-coupled receptors.
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Affiliation(s)
- Li Tian
- Department of Chemistry, Center for Diagnostics and Therapeutics, Advanced Translational Imaging FacilityGeorgia State UniversityAtlantaGeorgiaUSA
| | - Corey Andrews
- Department of Chemistry, Center for Diagnostics and Therapeutics, Advanced Translational Imaging FacilityGeorgia State UniversityAtlantaGeorgiaUSA
| | - Qiuyun Yan
- Department of Chemistry, Center for Diagnostics and Therapeutics, Advanced Translational Imaging FacilityGeorgia State UniversityAtlantaGeorgiaUSA
| | - Jenny J. Yang
- Department of Chemistry, Center for Diagnostics and Therapeutics, Advanced Translational Imaging FacilityGeorgia State UniversityAtlantaGeorgiaUSA
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2
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Kumar P, Yang Z, Lever JM, Chávez MD, Fatima H, Crossman DK, Maynard CL, George JF, Mitchell T. Hydroxyproline stimulates inflammation and reprograms macrophage signaling in a rat kidney stone model. Biochim Biophys Acta Mol Basis Dis 2022; 1868:166442. [PMID: 35562038 PMCID: PMC10101222 DOI: 10.1016/j.bbadis.2022.166442] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 05/04/2022] [Accepted: 05/06/2022] [Indexed: 11/17/2022]
Abstract
Meals rich in oxalate are associated with calcium oxalate (CaOx) kidney stone disease. Hydroxy-L-proline (HLP) is an oxalate precursor found in milk and collagen-containing foods. HLP has been shown to induce CaOx crystal formation in rodents. The purpose of this study was to evaluate the effect of HLP induced oxalate levels on inflammation and renal leukocytes during crystal formation. Male Sprague-Dawley rats (6-8 weeks old) were fed a control diet containing no oxalate for 3 days before being randomized to continue the control diet or 5% HLP for up to 28 days. Blood, 24 h urine, and kidneys were collected on Days 0, 7, 14, or 28. Urinary oxalate levels, crystal deposition, and renal macrophage markers were evaluated using ion chromatography-mass spectrometry, immunohistochemistry, and qRT-PCR. Renal leukocytes were assessed using flow cytometry and RNA-sequencing. HLP feeding increased urinary oxalate levels and renal crystal formation in animals within 7 days. HLP also increased renal macrophage populations on Days 14 and 28. Transcriptome analysis revealed that renal macrophages from animals fed HLP for 7 days were involved in inflammatory response and disease, stress response to LPS, oxidative stress, and immune cell trafficking. Renal macrophages isolated on Day 14 were involved in cell-mediated immunological pathways, ion homeostasis, and inflammatory response. Collectively, these findings suggest that HLP-mediated oxalate levels induce markers of inflammation, leukocyte populations, and reprograms signaling pathways in macrophages in a time-dependent manner. Additional studies investigating the significance of oxalate on renal macrophages could aid in our understanding of kidney stone formation.
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Affiliation(s)
- Parveen Kumar
- Department of Urology, University of Alabama Birmingham, Birmingham, AL, USA
| | - Zhengqin Yang
- Department of Nephrology, University of Alabama Birmingham, Birmingham, AL, USA
| | - Jeremie M Lever
- Department of Nephrology, University of Alabama Birmingham, Birmingham, AL, USA
| | - Miranda D Chávez
- Department of Urology, University of Alabama Birmingham, Birmingham, AL, USA
| | - Huma Fatima
- Department of Pathology, University of Alabama Birmingham, Birmingham, AL, USA
| | - David K Crossman
- Department of Medicine, University of Alabama Birmingham, Birmingham, AL, USA
| | - Craig L Maynard
- Department of Pathology, University of Alabama Birmingham, Birmingham, AL, USA
| | - James F George
- Department of Nephrology, University of Alabama Birmingham, Birmingham, AL, USA
| | - Tanecia Mitchell
- Department of Urology, University of Alabama Birmingham, Birmingham, AL, USA.
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3
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Penido MGMG, Tavares MDS. Beyond kidney stones: Why pediatricians should worry about hypercalciuria. World J Clin Pediatr 2021; 10:137-150. [PMID: 34868890 PMCID: PMC8603641 DOI: 10.5409/wjcp.v10.i6.137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 08/08/2021] [Accepted: 10/31/2021] [Indexed: 02/06/2023] Open
Abstract
The incidence of urolithiasis (UL) is increasing, and it has become more common in children and adolescents over the past few decades. Hypercalciuria is the leading metabolic risk factor of pediatric UL, and it has high morbidity, with or without lithiasis as hematuria and impairment of bone mass. The reduction in bone mineral density has already been described in pediatric idiopathic hypercalciuria (IH), and the precise mechanisms of bone loss or failure to achieve adequate bone mass gain remain unknown. A current understanding is that hypercalciuria throughout life can be considered a risk of change in bone structure and low bone mass throughout life. However, it is still not entirely known whether hypercalciuria throughout life can compromise the quality of the mass. The peak bone mass is achieved by late adolescence, peaking at the end of the second decade of life. This accumulation should occur without interference in order to achieve the peak of optimal bone mass. The bone mass acquired during childhood and adolescence is a major determinant of adult bone health, and its accumulation should occur without interference. This raises the critical question of whether adult osteoporosis and the risk of fractures are initiated during childhood. Pediatricians should be aware of this pediatric problem and investigate their patients. They should have the knowledge and ability to diagnose and initially manage patients with IH, with or without UL.
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Affiliation(s)
- Maria Goretti Moreira Guimarães Penido
- Pediatric Nephrology Unit, Nephrology Center, Santa Casa de Belo Horizonte Hospital, CEP 30150320, Belo Horizonte, Minas Gerais, Brazil
- Pediatric Nephrology Unit, Pediatric Department, Clinics Hospital, Universidade Federal de Minas Gerais, CEP 30130100, Belo Horizonte, Minas Gerais, Brazil
| | - Marcelo de Sousa Tavares
- Pediatric Nephrology Unit, Nephrology Center, Santa Casa de Belo Horizonte Hospital, CEP 30150320, Belo Horizonte, Minas Gerais, Brazil
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4
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Guo S, Chia W, Wang H, Bushinsky DA, Zhong B, Favus MJ. Vitamin D receptor (VDR) contributes to the development of hypercalciuria by sensitizing VDR target genes to vitamin D in a genetic hypercalciuric stone-forming (GHS) rat model. Genes Dis 2020; 9:797-806. [PMID: 35782986 PMCID: PMC9243318 DOI: 10.1016/j.gendis.2020.09.001] [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: 04/12/2020] [Revised: 09/08/2020] [Accepted: 09/09/2020] [Indexed: 12/03/2022] Open
Abstract
Human idiopathic hypercalciuria (IH) is the most common cause of calcium oxalate nephrolithiasis with perturbed calcium metabolism with increased bone resorption and decreased renal calcium reabsorption, which can be phenotype-copied in the genetic hypercalciuric stone-forming (GHS) rat model. We previously demonstrated that high VDR expression plays important roles in the development of hypercalciuria in the GHS rats. However, the underlying mechanism through which VDR impact hypercalciuria development remains to be fully understood. Here, we sought to determine how VDR regulated its target genes that are implicated in calcium homeostasis and potentially hypercalciuria. We found that VDR expression in the GHS rats was elevated in the calcium transporting tissues, as well as in the thymus and prostate, but not in lung, brain, heart, liver and spleen, when compared with control SD rats. Snail expression in the GHS rats was significantly downregulated in kidney, intestine, thymus and testis. Intraperitoneal injection of 1,25(OH)2D3 significantly upregulated the expression of renal calcium sensing receptor (CaSR), intestinal calcium transporters transient receptor potential vanilloid type 6 (TRPV6), and VDR in GHS rats, compared with that in control SD rats. ChIP assays revealed that VDR specifically bound to the proximal promoters of target genes, followed by histone H3 hyperacetylation or hypermethylation. Collectively, our results suggest that elevated VDR expression may contribute to the development of hypercalciuria by sensitizing VDR target genes to 1,25(OH)2D3 through histone modifications at their promoter regions in a genetic hypercalciuric stone-forming (GHS) rat model.
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5
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Chen X, Zhang XB, Li DJ, Qi GN, Dai YQ, Gu J, Chen MQ, Hu S, Liu ZY, Yang ZM. miR-155 facilitates calcium oxalate crystal-induced HK-2 cell injury via targeting PI3K associated autophagy. Exp Mol Pathol 2020; 115:104450. [PMID: 32417393 DOI: 10.1016/j.yexmp.2020.104450] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 12/17/2019] [Accepted: 05/10/2020] [Indexed: 12/20/2022]
Abstract
Nephrolithiasis is one of the most common and highly recurrent diseases worldwide. Accumulating evidence revealed the elevated miR-155 levels both in serum and urine of nephrolithiasis patients. The aim of our research was to explore the role of miR-155 in CaOx-induced apoptosis in HK-2 cells. The expression levels of miR-155 in serum and renal tissues were quantified in 20 patients with nephrolithiasis using qRT-PCR assay. ELISA was performed to determine urinary levels of interleukin (IL)-1β, IL-6 and tumor necrosis factor-alpha (TNF-α). Renal tubular cell model of CaOx nephrolithiasis was established to investigate the role and molelular mechanism of miR-155. Cell viability and apoptosis were assessed by MTT and flow cytometry, respectively. Immunofluoresent staining of LC3 autophagosome and western blotting were performed to evaluate the autophagic activity. Luciferase reporter assay was employed to verify the interaction between miR-155 and PI3KCA/Rheb. PI3K/Akt/mTOR signaling was further examined by western blotting. Serum and renal levels of miR-155 and inflammatory factors were significantly elevated in nephrolithiasis patients than in controls. CaOx treatment caused up-regulation of miR-155 and induced autophagy in renal tubular epithelial cells, while silencing miR-155 or inhibition of autophagy by 3-metheladenine (3-MA) ameliorated CaOx crystal-induced cell injury. PI3KCA and Rheb was identified as downstream targets of miR-155. Moreover, miR-155 activates autophagy and promotes cell injury through repressing PI3K/Akt/mTOR signaling pathway. Taken together, these findings demonstrated that miR-155 facilitates CaOx crystal-induced renal tubular epithelial cell injury via PI3K/Akt/mTOR-mediated autophagy, providing therapeutic targets for ameliorating cellular damage by CaOx crystals.
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Affiliation(s)
- Xiong Chen
- Department of Geriatric Urology, Xiangya International Medical Center, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China
| | - Xiao-Bo Zhang
- Department of Geriatric Urology, Xiangya International Medical Center, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China; Urolithiasis Institute of Central South University, Changsha 410008, Hunan Province, PR China
| | - Dong-Jie Li
- Department of Geriatric Urology, Xiangya International Medical Center, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China
| | - Guan-Nan Qi
- Department of Geriatric Urology, Xiangya International Medical Center, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China
| | - Yuan-Qing Dai
- National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China; Department of Geriatric Surgery, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China
| | - Jie Gu
- Department of Geriatric Urology, Xiangya International Medical Center, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China
| | - Ming-Quan Chen
- Department of Geriatric Urology, Xiangya International Medical Center, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China
| | - Sheng Hu
- Department of Geriatric Urology, Xiangya International Medical Center, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China
| | - Zhen-Yu Liu
- Department of Geriatric Urology, Xiangya International Medical Center, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China
| | - Zhi-Ming Yang
- Department of Geriatric Urology, Xiangya International Medical Center, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China; National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, PR China.
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Krieger NS, Chen L, Becker J, DeBoyace S, Wang H, Favus MJ, Bushinsky DA. Increased Osteoclast and Decreased Osteoblast Activity Causes Reduced Bone Mineral Density and Quality in Genetic Hypercalciuric Stone-Forming Rats. JBMR Plus 2020; 4:e10350. [PMID: 32258968 PMCID: PMC7117851 DOI: 10.1002/jbm4.10350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 02/09/2020] [Indexed: 11/16/2022] Open
Abstract
To study human idiopathic hypercalciuria (IH), we developed an animal model, genetic hypercalciuric stone-forming (GHS) rats, whose pathophysiology parallels that in IH. All GHS rats form kidney stones and have decreased BMD and bone quality compared with the founder Sprague-Dawley (SD) rats. To understand the bone defect, we characterized osteoclast and osteoblast activity in the GHS compared with SD rats. Bone marrow cells were isolated from femurs of GHS and SD rats and cultured to optimize differentiation into osteoclasts or osteoblasts. Osteoclasts were stained for TRAcP (tartrate resistant acid phosphatase), cultured to assess resorptive activity, and analyzed for specific gene expression. Marrow stromal cells or primary neonatal calvarial cells were differentiated to osteoblasts, and osteoblastic gene expression as well as mineralization was analyzed. There was increased osteoclastogenesis and increased resorption pit formation in GHS compared with SD cultures. Osteoclasts had increased expression of cathepsin K, Tracp, and MMP9 in cells from GHS compared with SD rats. Osteoblastic gene expression and mineralization was significantly decreased. Thus, alterations in baseline activity of both osteoclasts and osteoblasts in GHS rats, led to decreased BMD and bone quality, perhaps because of their known increase in vitamin D receptors. Better understanding of the role of GHS bone cells in decreased BMD and quality may provide new strategies to mitigate the low BMD and increased fracture risk found in patients with IH. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.
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Affiliation(s)
- Nancy S Krieger
- Division of NephrologyUniversity of Rochester School of MedicineRochesterNYUSA
| | - Luojing Chen
- Division of NephrologyUniversity of Rochester School of MedicineRochesterNYUSA
| | - Jennifer Becker
- Division of NephrologyUniversity of Rochester School of MedicineRochesterNYUSA
| | - Sean DeBoyace
- Division of NephrologyUniversity of Rochester School of MedicineRochesterNYUSA
| | - Hongwei Wang
- Section of EndocrinologyUniversity of Chicago Pritzker School of MedicineChicagoILUSA
| | - Murray J Favus
- Section of EndocrinologyUniversity of Chicago Pritzker School of MedicineChicagoILUSA
| | - David A Bushinsky
- Division of NephrologyUniversity of Rochester School of MedicineRochesterNYUSA
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Sensing Extracellular Calcium - An Insight into the Structure and Function of the Calcium-Sensing Receptor (CaSR). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1131:1031-1063. [PMID: 31646544 DOI: 10.1007/978-3-030-12457-1_41] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The calcium-sensing receptor (CaSR) is a G protein-coupled receptor that plays a key role in calcium homeostasis, by sensing free calcium levels in blood and regulating parathyroid hormone secretion in response. The CaSR is highly expressed in parathyroid gland and kidney where its role is well characterised, but also in other tissues where its function remains to be determined. The CaSR can be activated by a variety of endogenous ligands, as well as by synthetic modulators such as Cinacalcet, used in the clinic to treat secondary hyperparathyroidism in patients with chronic kidney disease. The CaSR couples to multiple G proteins, in a tissue-specific manner, activating several signalling pathways and thus regulating diverse intracellular events. The multifaceted nature of this receptor makes it a valuable therapeutic target for calciotropic and non-calciotropic diseases. It is therefore essential to understand the complexity behind the pharmacology, trafficking, and signalling characteristics of this receptor. This review provides an overview of the latest knowledge about the CaSR and discusses future hot topics in this field.
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8
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García Nieto VM, Luis Yanes MI, Tejera Carreño P, Perez Suarez G, Moraleda Mesa T. The idiopathic hypercalciuria reviewed. Metabolic abnormality or disease? Nefrologia 2019; 39:592-602. [PMID: 31160051 DOI: 10.1016/j.nefro.2019.02.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Revised: 02/02/2019] [Accepted: 02/20/2019] [Indexed: 02/08/2023] Open
Abstract
Idiopathic hypercalciuria (IH) is defined as that clinical situation in which an increase in urinary calcium excretion is observed, in the absence of hypercalcemia and other known causes of hypercalciuria. In recent years, its diagnosis in pediatric age has been more frequent because it has been known that it can debut with very different symptoms, in the absence of kidney stone formation. The discovery of genetic hypercalciuric stone-forming rats has allowed us to glimpse the pathophysiological mechanism of IH since they show many data in common with humans with IH as normal levels of blood calcium, intestinal calcium hyperabsorption, increased bone resorption and a defect in the renal tubular calcium reabsorption. In 1993, it was shown that in these animals there is an increase in the number of vitamin D receptors (VDR) in the intestine, which favors an increase in the functional capacity of calcitriol-VDR complexes that explains the increase in intestinal transport of calcium. The same happens at the bone level producing a greater resorption. In our opinion, IH is a 'metabolic anomaly' or, better, an inheritable constitutive metabolic characteristic. In this sense, what patients with IH would inherit is the availability of having a greater number of VDRs in their cells than those with normal urinary calcium excretion. IH cannot be considered a sensu stricto disease, so pharmacological treatment must be individualized.
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Affiliation(s)
- Víctor M García Nieto
- Sección de Nefrología Pediátrica, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, España.
| | - María Isabel Luis Yanes
- Sección de Nefrología Pediátrica, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, España
| | - Patricia Tejera Carreño
- Sección de Nefrología Pediátrica, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, España
| | - German Perez Suarez
- Servicio de Nefrología, Hospital Universitario Insular de Gran Canaria, Las Palmas de Gran Canaria, España
| | - Teresa Moraleda Mesa
- Sección de Nefrología Pediátrica, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, España
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Abstract
PURPOSE OF REVIEW With recent advances in sequencing technologies and increasing research into the gut microbiome (GMB), studies have revealed associations between the GMB and urinary stone disease (USD). We sought to determine whether the evidence pointed towards a few specific gut bacteria or the broader GMB network is seemingly responsible for this relationship. RECENT FINDINGS Initially, Oxalobacter formigenes (OF) was pursued as the main link between GMB and USD given its ability to degrade oxalate in the gut. However, the latest studies consistently suggest that the entire GMB is much more likely to be involved in handling oxalate absorption and other risk factors for urinary stone formation, rather than just a few microbiota. The GMB has complex networks that are likely involved in the pathophysiology of USD, although the causal mechanisms remain unclear. With increasing interest and research, potential modalities that act on the GMB may help to prevent incidence of USD.
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Affiliation(s)
- Justin A Lee
- Albert Einstein College of Medicine, 1300 Morris Park Ave, Bronx, NY, 10461, USA
| | - Joshua M Stern
- Department of Urology, Montefiore Medical Center, 1250 Waters Place - Tower 2 - 9th floor, Bronx, NY, 10461, USA.
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Stern JM, Urban‐Maldonado M, Usyk M, Granja I, Schoenfeld D, Davies KP, Agalliu I, Asplin J, Burk R, Suadicani SO. Fecal transplant modifies urine chemistry risk factors for urinary stone disease. Physiol Rep 2019; 7:e14012. [PMID: 30789675 PMCID: PMC6383111 DOI: 10.14814/phy2.14012] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 02/01/2019] [Accepted: 02/03/2019] [Indexed: 01/04/2023] Open
Abstract
Urinary stone disease (USD) is a major health concern. There is a need for new treatment modalities. Recently, our group provided evidence for an association between the GMB composition and USD. The accessibility of the Gut Microbiome (GMB) makes it an attractive target for investigation and therefore, in these studies we have evaluated the extent to which the whole gut microbial community in fecal transplants can affect urinary stone risk parameters in an animal model. Fresh fecal pellets were collected from Zucker lean rats, homogenized in PBS (100 mg/mL), filtered through a 70 μm strainer and then orally gavaged into C57BL/6NTac germ-free mice. Twenty-four hours urine collections and GMB analysis were performed over time for 1 month. Kidney and gut tissue were harvested from transplanted mice for western blot analysis of expression levels of the Slc26a6 transporter involved in oxalate balance. Urinary calcium decreased after fecal transplant by 55% (P < 0.001). Urinary oxalate levels were on average 24% lower than baseline levels (P < 0.001). Clostridiaceae family was negatively correlated with urinary oxalate at 4 weeks after transplant (r = -0.83, P < 0.01). There was a 0.6 unit average increase in urinary pH from a baseline of 5.85 (SE ± 0.028) to 6.49 (SE ± 0.04) (P < 0.001) after transplant. There was a concomitant 29% increase in gastrointestinal alkali absorption (P < 0.001) 4-weeks after fecal transplant. Slc26a6 expression increased by 90% in the cecum after transplant. Our results suggest that the gut microbiome may impact metabolism, alters urinary chemistry, and thereby may influence USD; the accessibility of the GMB can potentially be leveraged for therapeutic interventions.
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Affiliation(s)
- Joshua M. Stern
- Department of UrologyAlbert Einstein College of MedicineBronxNew York
| | | | - Mykhaylo Usyk
- Department of MicrobiologyAlbert Einstein College of MedicineBronxNew York
| | | | - Daniel Schoenfeld
- Department of UrologyAlbert Einstein College of MedicineBronxNew York
| | - Kelvin P. Davies
- Department of UrologyAlbert Einstein College of MedicineBronxNew York
| | - Ilir Agalliu
- Department of EpidemiologyAlbert Einstein College of MedicineBronxNew York
| | | | - Robert Burk
- Department of MicrobiologyAlbert Einstein College of MedicineBronxNew York
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Hendy GN, Canaff L. Calcium-Sensing Receptor Gene: Regulation of Expression. Front Physiol 2016; 7:394. [PMID: 27679579 PMCID: PMC5020072 DOI: 10.3389/fphys.2016.00394] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 08/23/2016] [Indexed: 12/13/2022] Open
Abstract
The human calcium-sensing receptor gene (CASR) has 8 exons, and localizes to chromosome 3q. Exons 1A and 1B encode alternative 5′-untranslated regions (UTRs) that splice to exon 2 encoding the AUG initiation codon. Exons 2–7 encode the CaSR protein of 1078 amino acids. Promoter P1 has TATA and CCAAT boxes upstream of exon 1A, and promoter P2 has Sp1/3 motifs at the start site of exon 1B. Exon 1A transcripts from the P1 promoter are reduced in parathyroid tumors and colon carcinomas. Studies of colon carcinomas and neuroblastomas have emphasized the importance of epigenetic changes—promoter methylation of the GC-rich P2 promoter, histone acetylation—as well as involvement of microRNAs in bringing about CASR gene silencing and reduced CaSR expression. Functional cis-elements in the CASR promoters responsive to 1,25-dihydroxyvitamin D [1,25(OH)2D], proinflammatory cytokines, and the transcription factor glial cells missing-2 (GCM2) have been characterized. Reduced levels of CaSR and reduced responsiveness to active vitamin D in parathyroid neoplasia and colon carcinoma may blunt the “tumor suppressor” activity of the CaSR. The hypocalcemia of critically ill patients with burn injury or sepsis is associated with CASR gene upregulation by TNF-alpha and IL-1beta via kappaB elements, and by IL-6 via Stat1/3 and Sp1/3 elements in the CASR gene promoters, respectively. The CASR is transactivated by GCM2—the expression of which is essential for parathyroid gland development. Hyperactive forms of GCM2 may contribute to later parathyroid hyperactivity or tumorigenesis. The expression of the CaSR—the calciostat—is regulated physiologically and pathophysiologically at the gene level.
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Affiliation(s)
- Geoffrey N Hendy
- Experimental Therapeutics and Metabolism, McGill University Health Centre-Research Institute, Departments of Medicine, Physiology, and Human Genetics, McGill University Montréal, QC, Canada
| | - Lucie Canaff
- Experimental Therapeutics and Metabolism, McGill University Health Centre-Research Institute, Departments of Medicine, Physiology, and Human Genetics, McGill University Montréal, QC, Canada
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12
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Sun J, Sun B, Wang W, Han X, Liu H, Du J, Feng W, Liu B, Amizuka N, Li M. Histochemical examination of the effects of high-dose 1,25(OH)2D3 on bone remodeling in young growing rats. J Mol Histol 2016; 47:389-99. [PMID: 27255234 DOI: 10.1007/s10735-016-9681-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 05/26/2016] [Indexed: 12/17/2022]
Abstract
Vitamin D has an anabolic effect on bone developmental processes and is involved in maintaining skeletal integrity. In recent years, pediatric cases of vitamin D intoxication have attracted attention. Therefore, the aim of this study was to investigate the influence of long-term administration of physiologically-high-dose calcitriol (1,25(OH)2D3) on bone remodeling in young developing rats. Neonatal rats received once-daily subcutaneous injection of calcitriol (250 ng/kg body weight), or PBS only as a control, for 3 weeks. At 1, 2 and 4 weeks' post-administration, rats were sacrificed and fixed by transcardial perfusion with 4 % paraformaldehyde, following which tibiae were extracted for histochemical analysis. Compared with the control group, the number of tartrate-resistant acid phosphatase- and Cathepsin K-positive osteoclasts were significantly increased, and the expression of alkaline phosphatase in osteoblasts was decreased in trabecular bone of rats administered high-dose 1,25(OH)2D3, leading to decreased trabecular bone volume. In addition, the expression of receptor activator of nuclear factor kappa-B ligand (RANKL) was increased, while that of osteoprotegerin was weaker in osteoblasts in the experimental group compared with the control group. Moreover, there was weaker immunoreactivity for EphrinB2 in osteoclasts and EphB4 in osteoblasts of trabecular bone in the experimental group compared with the control group. These findings suggest that long-term use of physiologically-high dose calcitriol may result in bone loss through RANKL/RANK/osteoprotegerin and EphrinB2-EphB4 signaling pathways, and that these negative effects could continue after drug withdrawal. Therefore, optimal limits for vitamin D administration need to be established for children and adolescents.
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Affiliation(s)
- Jing Sun
- Department of Bone Metabolism, School of Stomatology Shandong University, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Wenhua West Road 44-1, 250012, Jinan, China
| | - Bao Sun
- Department of Bone Metabolism, School of Stomatology Shandong University, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Wenhua West Road 44-1, 250012, Jinan, China
| | - Wei Wang
- Department of Bone Metabolism, School of Stomatology Shandong University, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Wenhua West Road 44-1, 250012, Jinan, China
| | - Xiuchun Han
- Department of Bone Metabolism, School of Stomatology Shandong University, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Wenhua West Road 44-1, 250012, Jinan, China
| | - Hongrui Liu
- Department of Bone Metabolism, School of Stomatology Shandong University, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Wenhua West Road 44-1, 250012, Jinan, China
| | - Juan Du
- Department of Bone Metabolism, School of Stomatology Shandong University, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Wenhua West Road 44-1, 250012, Jinan, China
| | - Wei Feng
- Department of Bone Metabolism, School of Stomatology Shandong University, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Wenhua West Road 44-1, 250012, Jinan, China
| | - Bo Liu
- Department of Bone Metabolism, School of Stomatology Shandong University, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Wenhua West Road 44-1, 250012, Jinan, China
| | - Norio Amizuka
- Department of Developmental Biology of Hard Tissue, Graduate School of Dental Medicine, Hokkaido University, Sapporo, Japan
| | - Minqi Li
- Department of Bone Metabolism, School of Stomatology Shandong University, Shandong Provincial Key Laboratory of Oral Tissue Regeneration, Wenhua West Road 44-1, 250012, Jinan, China.
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High Concentration of Calcium Stimulates Calcium Oxalate Crystal Attachment to Rat Tubular Epithelial NRK Cells Through Osteopontin. Urology 2015. [PMID: 26216642 DOI: 10.1016/j.urology.2015.07.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVE To address whether hypercalciuria can stimulate calcium oxalate (CaOx) crystal deposition in kidney through osteopontin (OPN). MATERIALS AND METHODS Rat tubular epithelial NRK cells were exposed to calcium. The cell viability, the cellular malondialdehyde content as a marker of reactive oxygen species (ROS), and the release of lactate dehydrogenase as markers of injury were detected. The production and gene expression of OPN were also examined. CaOx crystal attachment to cells was accomplished by measuring the calcium concentration of the cell lysates with atomic absorption analysis. RESULTS Exposure to calcium produced signs of cell injury and ROS-induced lipid peroxidation. The messenger ribonucleic acid expression and production of OPN increased significantly. OPN knockdown can significantly decrease the amount of CaOx crystal attachment to NRK cells. CONCLUSION In response to exposure to high concentration of calcium, renal tubular epithelial NRK cells increase the production of OPN, which may have a promoting role in CaOx crystal adhesion to NRK cells by calcium stimulation.
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The Wnt11 Signaling Pathway in Potential Cellular EMT and Osteochondral Differentiation Progression in Nephrolithiasis Formation. Int J Mol Sci 2015; 16:16313-29. [PMID: 26193266 PMCID: PMC4519952 DOI: 10.3390/ijms160716313] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 06/22/2015] [Accepted: 07/07/2015] [Indexed: 11/17/2022] Open
Abstract
The molecular events leading to nephrolithiasis are extremely complex. Previous studies demonstrated that calcium and transforming growth factor-β1 (TGF-β1) may participate in the pathogenesis of stone formation, but the explicit mechanism has not been defined. Using a self-created genetic hypercalciuric stone-forming (GHS) rat model, we observed that the increased level of serous/uric TGF-β1 and elevated intracellular calcium in primary renal tubular epithelial cells (PRECs) was associated with nephrolithiasis progression in vivo. In the setting of high calcium plus high TGF-β1 in vitro, PRECs showed great potential epithelial to mesenchymal transition (EMT) progression and osteochondral differentiation properties, representing the multifarious increased mesenchymal and osteochondral phenotypes (Zeb1, Snail1, Col2A1, OPN, Sox9, Runx2) and decreased epithelial phenotypes (E-cadherin, CK19) bythe detection of mRNAs and corresponding proteins. Moreover, TGF-β-dependent Wnt11 knockdown and L-type Ca2+ channel blocker could greatly reverse EMT progression and osteochondral differentiation in PRECs. TGF-β1 alone could effectively promote EMT, but it had no effect on osteochondral differentiation in NRK cells (Rat kidney epithelial cell line). Stimulation with Ca2+ alone did not accelerate differentiation of NRK. Co-incubation of extracellular Ca2+ and TGF-β1 synergistically promotes EMT and osteochondral differentiation in NRK control cells. Our data supplied a novel view that the pathogenesis of calcium stone development may be associated with synergic effects of TGF-β1 and Ca2+, which promote EMT and osteochondral differentiation via Wnt11 and the L-type calcium channel.
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Frick KK, Krieger NS, Bushinsky DA. Modeling hypercalciuria in the genetic hypercalciuric stone-forming rat. Curr Opin Nephrol Hypertens 2015; 24:336-44. [PMID: 26050120 PMCID: PMC4495578 DOI: 10.1097/mnh.0000000000000130] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW In this review, we discuss how the genetic hypercalciuric stone-forming (GHS) rats, which closely model idiopathic hypercalciuria and stone formation in humans, provide insights into the pathophysiology and consequences of clinical hypercalciuria. RECENT FINDINGS Hypercalciuria in the GHS rats is due to a systemic dysregulation of calcium transport, as manifest by increased intestinal calcium absorption, increased bone resorption and decreased renal tubule calcium reabsorption. Increased levels of vitamin D receptor in intestine, bone and kidney appear to mediate these changes. The excess receptors are biologically active and increase tissue sensitivity to exogenous vitamin D. Bones of GHS rats have decreased bone mineral density (BMD) as compared with Sprague-Dawley rats, and exogenous 1,25(OH)2D3 exacerbates the loss of BMD. Thiazide diuretics improve the BMD in GHS rats. SUMMARY Studying GHS rats allows direct investigation of the effects of alterations in diet and utilization of pharmacologic therapy on hypercalciuria, urine supersaturation, stone formation and bone quality in ways that are not possible in humans.
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Affiliation(s)
- Kevin K Frick
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
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Guha M, Bankura B, Ghosh S, Pattanayak AK, Ghosh S, Pal DK, Puri A, Kundu AK, Das M. Polymorphisms in CaSR and CLDN14 Genes Associated with Increased Risk of Kidney Stone Disease in Patients from the Eastern Part of India. PLoS One 2015; 10:e0130790. [PMID: 26107257 PMCID: PMC4480968 DOI: 10.1371/journal.pone.0130790] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 05/25/2015] [Indexed: 11/18/2022] Open
Abstract
Kidney stone disease (KSD) is a major clinical problem imposing a large burden for both healthcare and economy globally. In India, the prevalence of kidney stone disease is rapidly increasing. This study aimed to evaluate the association between genetic defects in vitamin D receptor (VDR), calcium sensing receptor (CaSR) and claudin 14 (CLDN14) genes and kidney stone disease in patients from eastern India. We enrolled 200 consecutive kidney stone patients (age 18-60 years) (cases) and their corresponding sex and age matched 200 normal individuals (controls). To identify genetic variants responsible for KSD, we performed sequence analysis of VDR, CaSR and CLDN14 genes. Four non-synonymous (rs1801725, rs1042636, rs1801726 and rs2228570), one synonymous (rs219780) and three intronic single nucleotide polymorphisms (SNPs) (rs731236, rs219777 and rs219778) were identified. Genotype and allele frequency analysis of these SNPs revealed that, rs1801725 (Ala986Ser), rs1042636 (Arg990Gly) of CaSR gene and rs219778, rs219780 (Thr229Thr) of CLDN14 gene were significantly associated with KSD. Serum calcium levels were significantly higher in subjects carrying 986Ser allele and calcium excretion was higher in subjects bearing 990Gly allele. In conclusion, rs1801725, rs1042636, rs219778 and rs219780 SNPs were associated with kidney stone risk in patients from the eastern part of India.
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Affiliation(s)
- Manalee Guha
- Department of Zoology, University of Calcutta, Kolkata, West Bengal, India
| | | | - Sudakshina Ghosh
- Department of Zoology, University of Calcutta, Kolkata, West Bengal, India
| | | | - Saurabh Ghosh
- Human Genetics Unit, Indian Statistical Institute, Kolkata, West Bengal, India
| | - Dilip Kumar Pal
- Department of Urology, Institute of Post Graduate Medical Education & Research, Kolkata, West Bengal, India
| | - Anurag Puri
- Department of Urology, Institute of Post Graduate Medical Education & Research, Kolkata, West Bengal, India
| | - Anup Kumar Kundu
- Department of Urology, Institute of Post Graduate Medical Education & Research, Kolkata, West Bengal, India
| | - Madhusudan Das
- Department of Zoology, University of Calcutta, Kolkata, West Bengal, India
- * E-mail:
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Mary A, Hénaut L, Boudot C, Six I, Brazier M, Massy ZA, Drüeke TB, Kamel S, Mentaverri R. Calcitriol prevents in vitro vascular smooth muscle cell mineralization by regulating calcium-sensing receptor expression. Endocrinology 2015; 156:1965-74. [PMID: 25763635 DOI: 10.1210/en.2014-1744] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Vascular calcification (VC) is a degenerative disease that contributes to cardiovascular morbidity and mortality. A negative relationship has been demonstrated between VC and calcium sensing receptor (CaSR) expression in the vasculature. Of interest, vitamin D response elements, which allow responsiveness to 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], are present in the promoters of the CaSR gene. We hypothesized that 1,25(OH)2D3, by modulating CaSR expression in vascular smooth muscle cells (VSMCs), might protect against VC. Human VSMCs were exposed to increasing concentrations of 1,25(OH)2D3 (0.01-10 nmol/L) in noncalcifying (1.8 mmol/L) or procalcifying Ca(2+)0 condition (5.0 mmol/L). Using quantitative RT-PCR and Western blotting we observed a significant increase in both CaSR mRNA and protein levels after exposure to 1.0 nmol/L 1,25(OH)2D3. This effect was associated with a maximal increase in CaSR expression at the cell surface after 48 hours of 1,25(OH)2D3 treatment, as assessed by flow cytometry. Down-regulation of the vitamin D receptor by small interfering RNA abolished these effects. In the procalcifying condition, 1.0 nmol/L 1,25(OH)2D3 blocked the Ca(2+)0-induced decrease in total and surface CaSR expression and protected against mineralization. Down-regulation of CaSR expression by CaSR small interfering RNA abolished this protective effect. 1,25(OH)2D3 concentrations of 0.5 and 5.0 nmol/L were also effective, but other (0.01, 0.1, and 10 nmol/L) concentrations did not modify CaSR expression and human VSMC mineralization. In conclusion, these findings suggest that nanomolar concentrations of 1,25(OH)2D3 induce a CaSR-dependent protection against VC. Both lower and higher concentrations are either ineffective or may even promote VC. Whether this also holds true in the clinical setting requires further study.
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Affiliation(s)
- Aurélien Mary
- INSERM Unit 1088 (A.M., L.H., C.B., I.B., M.B., Z.A.M., T.B.D., S.K., R.M.), University of Picardie Jules Vernes, 80000 Amiens, France; Department of Pharmacy (A.M.) and Department of Biochemistry (M.B., S.K., R.M.), Amiens University Medical Center, 80054 Amiens, France; Division of Nephrology (Z.A.M.), Ambroise Paré University Hospital, Assistance Publique-Hôpitaux de Paris, University Versailles Saint-Quentin-en-Yvelines, 92100 Boulogne Billancourt/Paris, France; and Multifaceted CaSR Initial Training Network (M.B., Z.A.M., S.K., R.M.)
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18
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Krieger NS, Asplin JR, Frick KK, Granja I, Culbertson CD, Ng A, Grynpas MD, Bushinsky DA. Effect of Potassium Citrate on Calcium Phosphate Stones in a Model of Hypercalciuria. J Am Soc Nephrol 2015; 26:3001-8. [PMID: 25855777 DOI: 10.1681/asn.2014121223] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 02/02/2015] [Indexed: 01/24/2023] Open
Abstract
Potassium citrate is prescribed to decrease stone recurrence in patients with calcium nephrolithiasis. Citrate binds intestinal and urine calcium and increases urine pH. Citrate, metabolized to bicarbonate, should decrease calcium excretion by reducing bone resorption and increasing renal calcium reabsorption. However, citrate binding to intestinal calcium may increase absorption and renal excretion of both phosphate and oxalate. Thus, the effect of potassium citrate on urine calcium oxalate and calcium phosphate supersaturation and stone formation is complex and difficult to predict. To study the effects of potassium citrate on urine supersaturation and stone formation, we utilized 95th-generation inbred genetic hypercalciuric stone-forming rats. Rats were fed a fixed amount of a normal calcium (1.2%) diet supplemented with potassium citrate or potassium chloride (each 4 mmol/d) for 18 weeks. Urine was collected at 6, 12, and 18 weeks. At 18 weeks, stone formation was visualized by radiography. Urine citrate, phosphate, oxalate, and pH levels were higher and urine calcium level was lower in rats fed potassium citrate. Furthermore, calcium oxalate and calcium phosphate supersaturation were higher with potassium citrate; however, uric acid supersaturation was lower. Both groups had similar numbers of exclusively calcium phosphate stones. Thus, potassium citrate effectively raises urine citrate levels and lowers urine calcium levels; however, the increases in urine pH, oxalate, and phosphate levels lead to increased calcium oxalate and calcium phosphate supersaturation. Potassium citrate induces complex changes in urine chemistries and resultant supersaturation, which may not be beneficial in preventing calcium phosphate stone formation.
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Affiliation(s)
- Nancy S Krieger
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York;
| | - John R Asplin
- Litholink Corporation, Laboratory Corporation of America Holdings, Chicago, Illinois; and
| | - Kevin K Frick
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York
| | - Ignacio Granja
- Litholink Corporation, Laboratory Corporation of America Holdings, Chicago, Illinois; and
| | - Christopher D Culbertson
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York
| | - Adeline Ng
- Laboratory Medicine and Pathobiology Department, University of Toronto, Toronto, Ontario, Canada
| | - Marc D Grynpas
- Laboratory Medicine and Pathobiology Department, University of Toronto, Toronto, Ontario, Canada
| | - David A Bushinsky
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York
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Kladnitsky O, Rozenfeld J, Azulay-Debby H, Efrati E, Zelikovic I. The claudin-16 channel gene is transcriptionally inhibited by 1,25-dihydroxyvitamin D. Exp Physiol 2014; 100:79-94. [PMID: 25557732 DOI: 10.1113/expphysiol.2014.083394] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 10/20/2014] [Indexed: 01/12/2023]
Abstract
NEW FINDINGS What is the central question of this study? In the kidney, the bulk of the filtered Mg(2+) is reabsorbed in the thick ascending limb by paracellular conductance, mediated by the tight junction protein, claudin-16, which is encoded by the gene CLDN16. The role of 1,25-dihydroxyvitamin D [1,25(OH)2 VitD] in renal Mg(2+) handling is unclear. We aimed to explore the molecular mechanisms underlying the effect of 1,25(OH)2 VitD on claudin-16-mediated Mg(2+) transport. What is the main finding and its importance? Paracellular, claudin-16-mediated Mg(2+) transport is transcriptionally repressed by 1,25(OH)2 VitD, probably via a Ca(2+)-sensing receptor-dependent mechanism. This renal effect of 1,25(OH)2 VitD may serve as an adaptive mechanism to the 1,25(OH)2 VitD-induced enteric hyperabsorption of dietary Mg(2+). Magnesium is reabsorbed in the thick ascending limb by paracellular conductance, mediated by the CLDN16-encoded tight junction protein, claudin-16. However, the role of 1,25-dihydroxyvitamin D [1,25(OH)2 VitD] in renal Mg(2+) handling is unclear. We have shown that Mg(2+) depletion increases and 1,25(OH)2 VitD inhibits CLDN16 transcription. We have now explored further the molecular mechanisms underlying the effect of 1,25(OH)2 VitD on claudin-16-mediated Mg(2+) transport. Adult mice received parenteral 1,25(OH)2 VitD or 1,25(OH)2 VitD combined with either high-Mg(2+) or low-Mg(2+) diets. Administration of 1,25(OH)2 VitD enhanced urinary excretion of Mg(2+) and Ca(2+). The 1,25(OH)2 VitD also increased renal Ca(2+)-sensing receptor (CaSR) mRNA and decreased renal claudin-16 and claudin-19 mRNA and claudin-16 protein, but did not affect renal claudin-2 mRNA. The 1,25(OH)2 VitD reversed the expected increase in claudin-16 mRNA in Mg(2+)-depleted animals. Comparably treated HEK 293 cells showed similar changes in claudin-16 mRNA, but 1,25(OH)2 VitD did not alter mRNA of the TRPM6 Mg(2+) channel. A luciferase reporter vector containing 2.5 kb of 5'-flanking DNA sequence from human CLDN16 (hCLDN16) was transfected into HEK 293 and OK cells. The hCLDN16 promoter activity was modestly decreased by 1,25(OH)2 VitD, but markedly inhibited in HEK 293 cells coexpressing CaSR. Coexpression in OK cells of dominant-negative CaSR completely abolished inhibition of hCLDN16 promoter activity by 1,25(OH)2 VitD. The 1,25(OH)2 VitD-induced decrease in hCLDN16 promoter activity was attenuated in Mg(2+)-depleted HEK 293 cells. In conclusion, 1,25(OH)2 VitD transcriptionally inhibits claudin-16 expression by a mechanism sensitive to CaSR and Mg(2+). This renal effect of 1,25(OH)2 VitD may serve as an adaptive response to the 1,25(OH)2 VitD-induced increase in intestinal Mg(2+) absorption.
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Affiliation(s)
- Orly Kladnitsky
- Laboratory of Developmental Nephrology, Department of Physiology and Biophysics, Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel
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Ng AH, Frick KK, Krieger NS, Asplin JR, Cohen-McFarlane M, Culbertson CD, Kyker-Snowman K, Grynpas MD, Bushinsky DA. 1,25(OH)₂D₃ induces a mineralization defect and loss of bone mineral density in genetic hypercalciuric stone-forming rats. Calcif Tissue Int 2014; 94:531-43. [PMID: 24481706 PMCID: PMC4276134 DOI: 10.1007/s00223-014-9838-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 01/07/2014] [Indexed: 11/29/2022]
Abstract
Genetic hypercalciuric stone-forming (GHS) rats, bred to maximize urine (u) calcium (Ca) excretion, demonstrate increased intestinal Ca absorption, increased bone Ca resorption, and reduced renal Ca reabsorption, all leading to elevated uCa compared to the parental Sprague-Dawley (SD) rats. GHS rats have increased numbers of vitamin D receptors (VDRs) at each site, with normal levels of 1,25(OH)₂D₃ (1,25D), suggesting their VDR is undersaturated with 1,25D. We have shown that 1,25D induces a greater increase in uCa in GHS than SD rats. To examine the effect of the increased VDR on the osseous response to 1,25D, we fed GHS and SD rats an ample Ca diet and injected either 1,25D [low dose (LD) 12.5 or high dose (HD) 25 ng/100 g body weight/day] or vehicle (veh) daily for 16 days. Femoral areal bone mineral density (aBMD, by DEXA) was decreased in GHS+LD and GHS+HD relative to GHS+veh, while there was no effect on SD. Vertebral aBMD was lower in GHS compared to SD and further decreased in GHS+HD. Both femoral and L6 vertebral volumetric BMD (by μCT) were lower in GHS and further reduced by HD. Histomorphometry indicated a decreased osteoclast number in GHS+HD compared to GHS+veh or SD+HD. In tibiae, GHS+HD trabecular thickness and number increased, with a 12-fold increase in osteoid volume but only a threefold increase in bone volume. Bone formation rate was decreased in GHS+HD relative to GHS+veh, confirming the mineralization defect. The loss of BMD and the mineralization defect in GHS rats contribute to increased hypercalciuria; if these effects persist, they would result in decreased bone strength, making these bones more fracture-prone. The enhanced effect of 1,25D in GHS rats indicates that the increased VDRs are biologically active.
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Affiliation(s)
- Adeline H. Ng
- Samuel Lunenfeld Research Institute, Toronto, Ontario, Canada
| | - Kevin K. Frick
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Nancy S. Krieger
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | | | | | - Christopher D. Culbertson
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Kelly Kyker-Snowman
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Marc D. Grynpas
- Samuel Lunenfeld Research Institute, Toronto, Ontario, Canada
| | - David A. Bushinsky
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
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Frick KK, Asplin JR, Culbertson CD, Granja I, Krieger NS, Bushinsky DA. Persistence of 1,25D-induced hypercalciuria in alendronate-treated genetic hypercalciuric stone-forming rats fed a low-calcium diet. Am J Physiol Renal Physiol 2014; 306:F1081-7. [PMID: 24573387 DOI: 10.1152/ajprenal.00680.2013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Genetic hypercalciuric stone-forming (GHS) rats demonstrate increased intestinal Ca absorption, increased bone resorption, and reduced renal tubular Ca reabsorption leading to hypercalciuria and all form kidney stones. GHS have increased vitamin D receptors (VDR) at these sites of Ca transport. Injection of 1,25(OH)2D3 (1,25D) leads to a greater increase in urine (u)Ca in GHS than in control Sprague-Dawley (SD), possibly due to the additional VDR. In GHS the increased uCa persists on a low-Ca diet (LCD) suggesting enhanced bone resorption. We tested the hypothesis that LCD, coupled to inhibition of bone resorption by alendronate (alen), would eliminate the enhanced 1,25D-induced hypercalciuria in GHS. SD and GHS were fed LCD and half were injected daily with 1,25D. After 8 days all were also given alen until euthanasia at day 16. At 8 days, 1,25D increased uCa in SD and to a greater extent in GHS. At 16 days, alen eliminated the 1,25D-induced increase in uCa in SD. However, in GHS alen decreased, but did not eliminate, the 1,25D-induced hypercalciuria, suggesting maximal alen cannot completely prevent the 1,25D-induced bone resorption in GHS, perhaps due to increased VDR. There was no consistent effect on mRNA expression of renal transcellular or paracellular Ca transporters. Urine CaP and CaOx supersaturation (SS) increased with 1,25D alone in both SD and GHS. Alen eliminated the increase in CaP SS in SD but not in GHS. If these results are confirmed in humans with IH, the use of bisphosphonates, such as alen, may not prevent the decreased bone density observed in these patients.
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Affiliation(s)
- Kevin K Frick
- Research Assistant Professor of Medicine, Univ. of Rochester School of Medicine and Dentistry, Division of Nephrology, Dept. of Medicine, 601 Elmwood Ave., Box 675, Rochester, NY 14642.
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Abstract
Hypercalciuria is the most common metabolic abnormality found in patients with calcium-containing kidney stones. Patients with hypercalciuria often excrete more calcium than they absorb, indicating a net loss of total-body calcium. The source of this additional urinary calcium is almost certainly the skeleton, the largest repository of calcium in the body. Hypercalciuric stone formers exhibit decreased bone mineral density (BMD), which is correlated with the increase in urine calcium excretion. The decreased BMD also correlates with an increase in markers of bone turnover as well as increased fractures. In humans, it is difficult to determine the cause of the decreased BMD in hypercalciuric stone formers. To study the effect of hypercalciuria on bone, we utilized our genetic hypercalciuric stone-forming (GHS) rats, which were developed through successive inbreeding of the most hypercalciuric Sprague-Dawley rats. GHS rats excrete significantly more urinary calcium than similarly fed controls, and all the GHS rats form kidney stones while control rats do not. The hypercalciuria is due to a systemic dysregulation of calcium homeostasis, with increased intestinal calcium absorption, enhanced bone mineral resorption, and decreased renal tubule calcium reabsorption associated with an increase in vitamin D receptors in all these target tissues. We recently found that GHS rats fed an ample calcium diet have reduced BMD and that their bones are more fracture-prone, indicating an intrinsic disorder of bone not secondary to diet. Using this model, we should better understand the pathogenesis of hypercalciuria and stone formation in humans to ultimately improve the bone health of patients with kidney stones.
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Affiliation(s)
- Nancy S Krieger
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine, 601 Elmwood Ave., Box 675, Rochester, NY, 14642, USA,
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Frick KK, Asplin JR, Krieger NS, Culbertson CD, Asplin DM, Bushinsky DA. 1,25(OH)₂D₃-enhanced hypercalciuria in genetic hypercalciuric stone-forming rats fed a low-calcium diet. Am J Physiol Renal Physiol 2013; 305:F1132-8. [PMID: 23926184 DOI: 10.1152/ajprenal.00296.2013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The inbred genetic hypercalciuric stone-forming (GHS) rats exhibit many features of human idiopathic hypercalciuria and have elevated levels of vitamin D receptors (VDR) in calcium (Ca)-transporting organs. On a normal-Ca diet, 1,25(OH)2D3 (1,25D) increases urine (U) Ca to a greater extent in GHS than in controls [Sprague-Dawley (SD)]. The additional UCa may result from an increase in intestinal Ca absorption and/or bone resorption. To determine the source, we asked whether 1,25D would increase UCa in GHS fed a low-Ca (0.02%) diet (LCD). With 1,25D, UCa in SD increased from 1.2 ± 0.1 to 9.3 ± 0.9 mg/day and increased more in GHS from 4.7 ± 0.3 to 21.5 ± 0.9 mg/day (P < 0.001). In GHS rats on LCD with or without 1,25D, UCa far exceeded daily Ca intake (2.6 mg/day). While the greater excess in UCa in GHS rats must be derived from bone mineral, there may also be a 1,25D-mediated decrease in renal tubular Ca reabsorption. RNA expression of the components of renal Ca transport indicated that 1,25D administration results in a suppression of klotho, an activator of the renal Ca reabsorption channel TRPV5, in both SD and GHS rats. This fall in klotho would decrease tubular reabsorption of the 1,25D-induced bone Ca release. Thus, the greater increase in UCa with 1,25D in GHS fed LCD strongly suggests that the additional UCa results from an increase in bone resorption, likely due to the increased number of VDR in the GHS rat bone cells, with a possible component of decreased renal tubular calcium reabsorption.
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Affiliation(s)
- Kevin K Frick
- Univ. of Rochester School of Medicine and Dentistry, Div. of Nephrology, Dept. of Medicine, 601 Elmwood Ave., Box 675, Rochester, NY 14642.
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Worcester EM, Bergsland KJ, Gillen DL, Coe FL. Evidence for increased renal tubule and parathyroid gland sensitivity to serum calcium in human idiopathic hypercalciuria. Am J Physiol Renal Physiol 2013; 305:F853-60. [PMID: 23863465 DOI: 10.1152/ajprenal.00124.2013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Patients with idiopathic hypercalciuria (IH) have decreased renal calcium reabsorption, most marked in the postprandial state, but the mechanisms are unknown. We compared 29 subjects with IH and 17 normal subjects (N) each fed meals providing identical amounts of calcium. Urine and blood samples were collected fasting and after meals. Levels of three candidate signalers, serum calcium (SCa), insulin (I), and plasma parathyroid hormone (PTH), did not differ between IH and N either fasting or fed, but all changed with feeding, and the change in SCa was greater in IH than in N. Regression analysis of fractional excretion of calcium (FECa) was significant for PTH and SCa in IH but not N. With the use of multivariable analysis, Sca entered the model while PTH and I did not. To avoid internal correlation we decomposed FECa into its independent terms: adjusted urine calcium (UCa) and UFCa molarity. Analyses using adjusted Uca and unadjusted Uca parallel those using FECa, showing a dominant effect of SCa with no effect of PTH or I. The effect of SCa may be mediated via vitamin D receptor-stimulated increased abundance of basolateral Ca receptor, which is supported by the fact PTH levels also seem more responsive to serum Ca in IH than in N. Although our data support an effect of SCa on FECa and UCa, which is more marked in IH than in N, it can account for only a modest fraction of the meal effect, perhaps 10-20%, suggesting additional mediators are also responsible for the exaggerated postprandial hypercalciuria seen in IH.
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Affiliation(s)
- Elaine M Worcester
- Nephrology Section MC 5100, Univ. of Chicago Medicine, 5841 South Maryland Ave., Chicago, IL 60637.
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He Y, Perry B, Bi M, Sun H, Zhao T, Li Y, Sun C. Allosteric regulation of the calcium-sensing receptor in obese individuals. Int J Mol Med 2013; 32:511-8. [PMID: 23740560 DOI: 10.3892/ijmm.2013.1408] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 05/24/2013] [Indexed: 11/06/2022] Open
Abstract
We have previously reported that the calcium-sensing receptor (CaSR) plays an important role in modulating lipid metabolism under low calcium conditions. The aim of this study was to identify possible regulators of CaSR and the mechanisms of action of CaSR in obese individuals. Subcutaneous fat samples were obtained from 10 obese and 10 non-obese males undergoing elective abdominal surgery. Visceral fat pads were obtained from 12 obese and 12 non-obese male rats. Serum lipid, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) concentrations, as well as the gene and protein expression of CaSR in the white adipose tissue of obese subjects and rats were determined. Serum total calcium, vitamin D, parathyroid hormone (PTH) and amino acid levels in human subjects were measured. Intracellular calcium and cyclic adenosine monophosphate (cAMP) levels in rat adipocytes were measured by laser scanning confocal microscopy and ELISA, respectively. The results revealed that serum triglyceride (TG), total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C), TNF-α, IL-6 and PTH levels were significantly higher in the obese individuals versus the controls. By contrast, serum vitamin D and amino acid concentrations were lower in the obese individuals versus the controls. In addition, intracellular calcium levels were higher, while cAMP levels were lower in the obese rat adipocytes compared with the control group. However, the gene and protein expression of CaSR in white adipose tissue did not differ between the obese groups and the controls. Thus, these results suggest that CaSR functions not through its expression, but rather through allosteric regulation in obese individuals.
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Affiliation(s)
- Yonghan He
- National Key Discipline of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China
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Hendy GN, Canaff L, Cole DEC. The CASR gene: alternative splicing and transcriptional control, and calcium-sensing receptor (CaSR) protein: structure and ligand binding sites. Best Pract Res Clin Endocrinol Metab 2013; 27:285-301. [PMID: 23856260 DOI: 10.1016/j.beem.2013.02.009] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The calcium-sensing receptor (CaSR) is a G protein-coupled receptor encoded by a single copy gene. The human CASR gene spans ~103-kb and has eight exons. Promoters P1 and P2 drive transcription of exons 1A and 1B, respectively, encoding alternative 5'-UTRs that splice to exon 2 encoding the common part of the 5'-UTR. Exons 2-7 encode the CaSR protein of 1078 amino acids. Functional elements responsive to 1,25-dihydroxyvitamin D, proinflammatory cytokines, and glial cells missing-2 are present in the CASR promoters. Evolutionarily, the exon structure, first seen in aquatic vertebrates, is well-conserved with a single linkage disequilibrium haplotype block for protein coding exons 2-7. Structural features of the human CaSR protein are: an N-terminal signal peptide (19 amino acids (aa)); an extracellular domain (~600 aa) having a bi-lobed Venus Flytrap (VFT) domain with several Ca(2+)-binding sites; and a nine-cysteines domain that transduces the activation signal to the 7-transmembrane domain (250 aa) and the C-terminal tail (216 aa).
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Affiliation(s)
- Geoffrey N Hendy
- Calcium Research Laboratory, and Hormones and Cancer Research Unit, Royal Victoria Hospital and McGill University Health Centre, Montreal, QC H3A 1A1, Canada.
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Lu'o'ng KVQ, Nguyen LTH. The role of vitamin D in Alzheimer's disease: possible genetic and cell signaling mechanisms. Am J Alzheimers Dis Other Demen 2013; 28:126-36. [PMID: 23322908 PMCID: PMC10852937 DOI: 10.1177/1533317512473196] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Alzheimer's disease (AD) is the most common form of dementia in the elderly individuals and is associated with progressive memory loss and cognitive dysfunction. A significant association between AD and low levels of vitamin D has been demonstrated. Furthermore, vitamin D supplements appear to have a beneficial clinical effect on AD by regulating micro-RNA, enhancing toll-like receptors, modulating vascular endothelial factor expression, modulating angiogenin, and advanced glycation end products. Vitamin D also exerts its effects on AD by regulating calcium-sensing receptor expression, enhancing amyloid-β peptides clearance, interleukin 10, downregulating matrix metalloproteinases, upregulating heme oxygenase 1, and suppressing the reduced form of nicotinamide adenine dinucleotide phosphate expression. In conclusion, vitamin D may play a beneficial role in AD. Calcitriol is the best vitamin D supplement for AD, because it is the active form of the vitamin D3 metabolite and modulates inflammatory cytokine expression. Therefore, further investigation of the role of calcitriol in AD is needed.
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Affiliation(s)
- Khanh Vinh Quoc Lu'o'ng
- Vietnamese American Medical Research Foundation, 14971 Brookhurst St. Westminster, CA 92683, USA.
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Frick KK, Asplin JR, Favus MJ, Culbertson C, Krieger NS, Bushinsky DA. Increased biological response to 1,25(OH)(2)D(3) in genetic hypercalciuric stone-forming rats. Am J Physiol Renal Physiol 2013; 304:F718-26. [PMID: 23344574 DOI: 10.1152/ajprenal.00645.2012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Genetic hypercalciuric stone-forming (GHS) rats, bred to maximize urine (U) calcium (Ca) excretion, have increased intestinal Ca absorption and bone Ca resorption and reduced renal Ca reabsorption, leading to increased UCa compared with the Sprague-Dawley (SD) rats. GHS rats have increased vitamin D receptors (VDR) at each of these sites, with normal levels of 1,25(OH)(2)D(3) (1,25D), indicating that their VDR is undersaturated with 1,25D. We tested the hypothesis that 1,25D would induce a greater increase in UCa in GHS rats by feeding both strains ample Ca and injecting 1,25D (25 ng · 100 g body wt(-1) · day(-1)) or vehicle for 16 days. With 1,25D, UCa in SD increased from 1.7 ± 0.3 mg/day to 24.4 ± 1.2 (Δ = 22.4 ± 1.5) and increased more in GHS from 10.5 ± 0.7 to 41.9 ± 0.7 (Δ = 29.8 ± 1.8; P = 0.003). To determine the mechanism of the greater increase in UCa in GHS rats, we measured kidney RNA expression of components of renal Ca transport. Expression of transient receptor potential vanilloid (TRPV)5 and calbindin D(28K) were increased similarly in SD + 1,25D and GHS + 1,25D. The Na(+)/Ca(2+) exchanger (NCX1) was increased in GHS + 1,25D. Klotho was decreased in SD + 1,25D and GHS + 1,25D. TRPV6 was increased in SD + 1,25D and increased further in GHS + 1,25D. Claudin 14, 16, and 19, Na/K/2Cl transporter (NKCC2), and secretory K channel (ROMK) did not differ between SD + 1,25D and GHS + 1,25D. Increased UCa with 1,25D in GHS exceeded that of SD, indicating that the increased VDR in GHS induces a greater biological response. This increase in UCa, which must come from the intestine and/or bone, must exceed any effect of 1,25D on TRPV6 or NCX1-mediated renal Ca reabsorption.
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Affiliation(s)
- Kevin K Frick
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.
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Moreira Guimarães Penido MG, de Sousa Tavares M. Bone disease in pediatric idiopathic hypercalciuria. World J Nephrol 2012; 1:54-62. [PMID: 24175242 PMCID: PMC3782196 DOI: 10.5527/wjn.v1.i2.54] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2011] [Revised: 11/11/2011] [Accepted: 02/10/2012] [Indexed: 02/06/2023] Open
Abstract
Idiopathic hypercalciuria (IH) is the leading metabolic risk factor for urolithiasis and affects all age groups without gender or race predominance. IH has a high morbidity with or without lithiasis and reduced bone mineral density (BMD), as described previously in pediatric patients as well as in adults. The pathogenesis of IH is complex and not completely understood, given that urinary excretion of calcium is the end result of an interplay between three organs (gut, bone and kidney), which is further orchestrated by hormones, such as 1,25 dihydroxyvitamin D, parathyroid hormone, calcitonin and fosfatonins (i.e., fibroblast growth-factor-23). Usually, a primary defect in one organ induces compensatory mechanisms in the remaining two organs, such as increased absorption of calcium in the gut secondary to a primary renal loss. Thus, IH is a systemic abnormality of calcium homeostasis with changes in cellular transport of this ion in intestines, kidneys and bones. Reduced BMD has been demonstrated in pediatric patients diagnosed with IH. However, the precise mechanisms of bone loss or failure of adequate bone mass gain are still unknown. The largest accumulation of bone mass occurs during childhood and adolescence, peaking at the end of the second decade of life. This accumulation should occur without interference to achieve the peak of optimal bone mass. Any interference may be a risk factor for the reduction of bone mass with increased risk of fractures in adulthood. This review will address the pathogenesis of IH and its consequence in bone mass.
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Affiliation(s)
- Maria Goretti Moreira Guimarães Penido
- Maria Goretti Moreira Guimarães Penido, Marcelo de Sousa Tavares, Department of Pediatrics, Pediatric Nephrology Unit, School of Medicine, Federal University of Minas Gerais, Belo Horizonte, Belo Horizonte, CEP 30130100, Minas Gerais, Brazil
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Xi QL, Wang SG, Ye ZQ, Zhu ZW, Li C, Bai J, Yu X, Liu JH. Effect of Silencing VDR Gene in Kidney on Renal Epithelial Calcium Transporter Proteins and Urinary Calcium Excretion in Genetic Hypercalciuric Stone-forming Rats. Urology 2011; 78:1442.e1-7. [DOI: 10.1016/j.urology.2011.08.051] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 08/26/2011] [Accepted: 08/26/2011] [Indexed: 11/25/2022]
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Xi Q, Wang S, Ye Z, Liu J, Yu X, Zhu Z, Su S, Bai J, Li C. Adenovirus-delivered microRNA targeting the vitamin D receptor reduces intracellular Ca²⁺ concentrations by regulating the expression of Ca²⁺-transport proteins in renal epithelial cells. BJU Int 2011; 107:1314-9. [PMID: 20553254 DOI: 10.1111/j.1464-410x.2010.09444.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
UNLABELLED What’s known on the subject? and What does the study add? Experimental data have shown that VDR overexpression in the duodenum and kidney cortex is a biological characteristic of genetic hypercalciuric stone-forming rats (GHS rat), and a link between idiopathic calcium stone formation and the microstatellite marker D12S339 (near the VDR locus) has been proven in humans. Our study shows that VDR can positively regulate the mRNA and protein expression of TRPV5, calbindin-D28k and PMCA1b in NRK cell lines. VDR knockdown results in a decrease in intracellular Ca²⁺ concentration in NRK cell lines. The effect of the elevated VDR level in the kidney on hypercalciuria and the underlying mechanisms need to be further addressed. OBJECTIVE • To determine the effects of vitamin D receptor (VDR) on hypercalciuria and the mechanisms underlying such effects. MATERIALS AND METHODS • The adenovirus vector-delivered microRNA targeting rat VDR was constructed. We infected the normal rat kidney epithelial cell line NRK (Cellbank, China) with the adenovirus and then collected the cells at 0, 48, 72, 96, 120 h after infection. The mRNA and protein levels of VDR and VDR-dependent epithelial Ca2+ transport proteins were detected using real-time polymerase chain reaction and Western blot assays, respectively. • Fluorescent Ca²⁺ indicator Fluo-4 NW (Fluo-4 NW calcium assay kit, Molecular Probes, Invitrogen, USA) and laser scanning confocal microscope (Olympus, FV500-IX71, Japan) were used to detect the cytosolic free Ca²⁺ concentration at different time points after infection. RESULTS • The mRNA and protein level of VDR, transient receptor potential vanilloid receptor subtype 5 (TRPV5), calbindin-D28k and plasma membrane Ca²⁺-ATPase (PMCA1b) in infected NRK cells was significantly lower at 72 and 96 h after infection than that in control cells. • There was no significant difference between the two groups in the mRNA and protein level of TRPV6 and the Na⁺/Ca²⁺-exchanger (NCX1). • Furthermore, VDR knockdown results in a decrease in intracellular Ca²⁺ concentration ([Ca²⁺]i) in NRK cell lines. CONCLUSIONS • Our study shows that VDR can positively regulate the mRNA and protein expression of TRPV5, calbindin-D28k and PMCA1b, but not of TRPV6 or NCX1, in NRK cell lines. VDR knockdown results in a decrease in [Ca²⁺]i in NRK cell lines. • The effect of the elevated VDR level in the kidney on hypercalciuria and the mechanisms underlying need to be further addressed.
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Affiliation(s)
- Qilin Xi
- Department of Urology, Tongji Hospital, Tongji Medical College of Huazhong University of Science and Technology, Wuhan, HuBei, China
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Kumar R, Thompson JR. The regulation of parathyroid hormone secretion and synthesis. J Am Soc Nephrol 2010; 22:216-24. [PMID: 21164021 DOI: 10.1681/asn.2010020186] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Secondary hyperparathyroidism classically appears during the course of chronic renal failure and sometimes after renal transplantation. Understanding the mechanisms by which parathyroid hormone (PTH) synthesis and secretion are normally regulated is important in devising methods to regulate overactivity and hyperplasia of the parathyroid gland after the onset of renal insufficiency. Rapid regulation of PTH secretion in response to variations in serum calcium is mediated by G-protein coupled, calcium-sensing receptors on parathyroid cells, whereas alterations in the stability of mRNA-encoding PTH by mRNA-binding proteins occur in response to prolonged changes in serum calcium. Independent of changes in intestinal calcium absorption and serum calcium, 1α,25-dihydroxyvitamin D also represses the transcription of PTH by associating with the vitamin D receptor, which heterodimerizes with retinoic acid X receptors to bind vitamin D-response elements within the PTH gene. 1α,25-Dihydroxyvitamin D additionally regulates the expression of calcium-sensing receptors to indirectly alter PTH secretion. In 2°HPT seen in renal failure, reduced concentrations of calcium-sensing and vitamin D receptors, and altered mRNA-binding protein activities within the parathyroid cell, increase PTH secretion in addition to the more widely recognized changes in serum calcium, phosphorus, and 1α,25-dihydroxyvitamin D. The treatment of secondary hyperparathyroidism by correction of serum calcium and phosphorus concentrations and the administration of vitamin D analogs and calcimimetic agents may be augmented in the future by agents that alter the stability of mRNA-encoding PTH.
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Affiliation(s)
- Rajiv Kumar
- Division of Nephrology and Hypertension, Departments of Medicine, Biochemistry and Molecular Biology, Mayo Clinic and Foundation, 200 1 Street SW, Rochester, MN 55905, USA.
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Pérez A, Centeno VA, Tolosa de Talamoni NG. Molecular mechanisms involved in the enhancement of mitochondrial malate dehydrogenase activity by calcitriol in chick intestine. J Nutr Biochem 2010; 21:1232-7. [DOI: 10.1016/j.jnutbio.2009.10.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Revised: 10/14/2009] [Accepted: 10/27/2009] [Indexed: 01/01/2023]
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Bai S, Wang H, Shen J, Zhou R, Bushinsky DA, Favus MJ. Elevated vitamin D receptor levels in genetic hypercalciuric stone-forming rats are associated with downregulation of Snail. J Bone Miner Res 2010; 25:830-40. [PMID: 19929616 PMCID: PMC3153334 DOI: 10.1359/jbmr.091010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2009] [Revised: 09/21/2009] [Accepted: 10/09/2009] [Indexed: 11/18/2022]
Abstract
Patients with idiopathic hypercalciuria (IH) and genetic hypercalciuric stone-forming (GHS) rats, an animal model of IH, are both characterized by normal serum Ca, hypercalciuria, Ca nephrolithiasis, reduced renal Ca reabsorption, and increased bone resorption. Serum 1,25-dihydroxyvitamin D [1,25(OH)(2)D] levels are elevated or normal in IH and are normal in GHS rats. In GHS rats, vitamin D receptor (VDR) protein levels are elevated in intestinal, kidney, and bone cells, and in IH, peripheral blood monocyte VDR levels are high. The high VDR is thought to amplify the target-tissue actions of normal circulating 1,25(OH)(2)D levels to increase Ca transport. The aim of this study was to elucidate the molecular mechanisms whereby Snail may contribute to the high VDR levels in GHS rats. In the study, Snail gene expression and protein levels were lower in GHS rat tissues and inversely correlated with VDR gene expression and protein levels in intestine and kidney cells. In human kidney and colon cell lines, ChIP assays revealed endogenous Snail binding close to specific E-box sequences within the human VDR promoter region, whereas only one E-box specifically bound Snail in the rat promoter. Snail binding to rat VDR promoter E-box regions was reduced in GHS compared with normal control intestine and was accompanied by hyperacetylation of histone H(3). These results provide evidence that elevated VDR in GHS rats likely occurs because of derepression resulting from reduced Snail binding to the VDR promoter and hyperacetylation of histone H(3).
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Affiliation(s)
- Shaochun Bai
- Section of Endocrinology and Metabolism, The University of Chicago Pritzker School of MedicineChicago, IL, USA
| | - Hongwei Wang
- Section of Endocrinology and Metabolism, The University of Chicago Pritzker School of MedicineChicago, IL, USA
| | - Jikun Shen
- Section of Endocrinology and Metabolism, The University of Chicago Pritzker School of MedicineChicago, IL, USA
| | - Randal Zhou
- Section of Endocrinology and Metabolism, The University of Chicago Pritzker School of MedicineChicago, IL, USA
| | - David A Bushinsky
- Department of Medicine, University of Rochester School of MedicineRochester, New York, USA
| | - Murray J Favus
- Section of Endocrinology and Metabolism, The University of Chicago Pritzker School of MedicineChicago, IL, USA
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Novel Ca receptor signaling pathways for control of renal ion transport. Curr Opin Nephrol Hypertens 2010; 19:106-12. [DOI: 10.1097/mnh.0b013e328332e7b2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Abstract
Kidney stone patients often have a decrease in BMD. It is unclear if reduced BMD is caused by a primary disorder of bone or dietary factors. To study the independent effects of hypercalciuria on bone, we used genetic hypercalciuric stone-forming (GHS) rats. GHS and control (Ctl) rats were fed a low Ca (0.02% Ca, LCD) or a high Ca (1.2% Ca, HCD) diet for 6 wk in metabolic cages. All comparisons are to Ctl rats. Urine Ca was greater in the GHS rats on both diets. GHS fed HCD had reduced cortical (humerus) and trabecular (L(1)-L(5) vertebrae) BMD, whereas GHS rats fed LCD had a reduction in BMD similar to Ctl. GHS rats fed HCD had a decrease in trabecular volume and thickness, whereas LCD led to a approximately 20-fold increase in both osteoid surface and volume. GHS rats fed HCD had no change in vertebral strength (failure stress), ductibility (failure strain), stiffness (modulus), or toughness, whereas in the humerus, there was reduced ductibility and toughness and an increase in modulus, indicating that the defect in mechanical properties is mainly manifested in cortical, rather than trabecular, bone. GHS rat cortical bone is more mineralized than trabecular bone and LCD led to a decrease in the mineralization profile. Thus, the GHS rats, fed an ample Ca diet, have reduced BMD with reduced trabecular volume, mineralized volume, and thickness, and their bones are more brittle and fracture prone, indicating that GHS rats have an intrinsic disorder of bone that is not secondary to diet.
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Hendy GN, Guarnieri V, Canaff L. Chapter 3 Calcium-Sensing Receptor and Associated Diseases. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 89:31-95. [DOI: 10.1016/s1877-1173(09)89003-0] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Bevilacqua M, Dominguez LJ, Gandolini G, Valdes V, Vago T, Righini V, Barrella M, Barbagallo M. Vitamin D substrate-product relationship in idiopathic hypercalciuria. J Steroid Biochem Mol Biol 2009; 113:3-8. [PMID: 19013526 DOI: 10.1016/j.jsbmb.2008.08.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Accepted: 08/06/2008] [Indexed: 11/16/2022]
Abstract
Absorptive hypercalciuria (AH) is associated with elevated levels of 1,25-dihydroxyvitamin D (1,25(OH)(2)D). While no increase of 1,25(OH)(2)D after oral administration of 25-hydroxyvitamin D (25OHD) at high doses has been claimed in normal subjects, a substrate-product relationship has been reported in normal children, young people after UV irradiation, older persons, postmenopausal women, primary hyperparathyroidism, renal failure, osteomalacia, and sarcoidosis. No data of this relationship in AH is available. To investigate 25OHD-1,25(OH)(2)D substrate-product relationship in AH, 161 AH patients (mean age 60.9+/-11.7 years) and 110 age- and sex-matched controls (mean age 61.5+/-12.4 years) were studied. In 57 controls and 52 AH subjects 25OHD-1,25(OH)(2)D relationship in basal conditions and after 2-week oral 25OHD (25 microg/day) administration were evaluated. In basal conditions 25OHD and 1,25(OH)(2)D were correlated in both, controls and AH; 25OHD treatment was followed by an increase in serum 25OHD and 1,25(OH)(2)D in both groups. However, delta responses of 25OHD and 1,25(OH)(2)D to 25OHD were higher in AH suggesting an enhanced activity of 1 alpha-hydroxylase. In conclusion, the higher response of 1,25(OH)(2)D after oral 25OHD in AH patients suggests a differential capacity between both groups in handling the increases in 1,25(OH)(2)D.
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Affiliation(s)
- Maurizio Bevilacqua
- Endocrinology and Diabetes Unit, Department of Medicine, Luigi Sacco Hospital (Vialba), University of Milan, Italy
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Carrillo-Lopez N, Alvarez-Hernandez D, Gonzalez-Suarez I, Roman-Garcia P, Valdivielso JM, Fernandez-Martin JL, Cannata-Andia JB. Simultaneous changes in the calcium-sensing receptor and the vitamin D receptor under the influence of calcium and calcitriol. Nephrol Dial Transplant 2008; 23:3479-84. [DOI: 10.1093/ndt/gfn338] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Abstract
Idiopathic hypercalciuria (IH) is the most common metabolic abnormality in patients with calcium kidney stones. It is characterized by normocalcemia, absence of diseases that cause increased urine calcium, and calcium excretion that is greater than 250 mg/d in women and 300 mg/d in men. Subjects with IH have a generalized increase in calcium turnover, which includes increased gut calcium absorption, decreased renal calcium reabsorption, and a tendency to lose calcium from bone. Despite the increase in intestinal calcium absorption, a negative calcium balance is seen commonly in balance studies, especially on a low-calcium diet. The mediator of decreased renal calcium reabsorption is not clear; it is not associated with either an increase in filtered load of calcium or altered parathyroid hormone levels. There is an increased incidence of hypercalciuria in first-degree relatives of those with IH, but IH appears to be a complex polygenic trait with a large contribution from diet to expression of increased calcium excretion. Increased tissue vitamin D response may be responsible for the manifestations of IH in at least some patients.
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Affiliation(s)
- Elaine M Worcester
- Nephrology Section, Department of Medicine, University of Chicago, Chicago, IL 60637, USA.
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Effect of bolus and divided feeding on urine ions and supersaturation in genetic hypercalciuric stone-forming rats. Kidney Int 2007; 73:423-9. [PMID: 18046318 DOI: 10.1038/sj.ki.5002699] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Because urine ion excretion varies throughout the day, clinicians monitor 24 h urine samples to measure ion excretion and supersaturation in kidney stone patients. However, these results are averages and may not reflect maximal supersaturation which drives stone formation. We measured ion excretion and saturation in genetic hypercalciuric stone-forming rats on both a normal or low calcium diet over 0-3, 3-6 and 6-24 h using two feeding protocols, where the daily food allotment was fed either as a bolus or divided into three portions. With a normal calcium diet, urine calcium, oxalate, volume, and calcium oxalate supersaturation were significantly greater on the bolus compared to the divided feeds in the prandial and postprandial periods. Bolus eaters also excreted more calcium and oxalate and had increased volume over 24 h. Maximal calcium oxalate supersaturation was greater during the initial time periods than during the entire 24 h, regardless of the feeding schedule. With the low calcium diet, the effect of bolus feeding was reduced. Thus, urine ion excretion and supersaturation vary with the type of feeding. If these results are confirmed in man, it suggests that eating as a bolus may result in greater prandial and postprandial calcium oxalate supersaturation. This may increase growth on Randall's plaques and promote stone disease.
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Abstract
Hypercalcuria is the most common metabolic disorder found in patients with nephrolithiasis. As the prevalence of kidney stones rises in industrialized nations, understanding the pathogenesis and treatment of hypercalciuria becomes increasingly important. Idiopathic hypercalciuria (IH), defined as an excess urine calcium excretion without an apparent underlying etiology, is the most frequent cause of hypercalciuria and will be the focus of this paper. Calcium homeostasis is tightly controlled and slight disturbances in transport at the level of the intestine, bone, and/or kidney can lead to excessive urine calcium excretion and promote stone formation. IH is a systemic disorder with dysregulation of calcium transport at a combination of these calcium regulatory sites. The goal of treatment is to prevent stone formation and relies on a combination of dietary and pharmaceutical interventions. Dietary management includes increasing fluid intake, salt restriction, animal protein restriction, and maintaining a normal calcium intake. Thiazide diuretics have proven effective in preventing calcium stone formation by reducing the urinary excretion of calcium. It is important to note that while decreasing urinary calcium excretion is important the clinician should focus primarily on reducing the supersaturation of calcium oxalate as this determines the true tendency for stone formation.
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Affiliation(s)
- Scott E Liebman
- University of Rochester School of Medicine and Dentistry, Nephrology Division, Strong Memorial Hospital, 601 Elmwood Avenue, Box 675, Rochester, NY 14642, USA.
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Ortiz-Capisano MC, Ortiz PA, Garvin JL, Harding P, Beierwaltes WH. Expression and function of the calcium-sensing receptor in juxtaglomerular cells. Hypertension 2007; 50:737-43. [PMID: 17785631 DOI: 10.1161/hypertensionaha.107.095158] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Calcium-sensing receptors sense and translate micromolar changes of extracellular calcium into changes in intracellular calcium. Renin, a component of the renin-angiotensin system, is synthesized by, stored in, and released from the juxtaglomerular cells through a cAMP-dependent pathway. Increased intracellular calcium inhibits the adenylyl cyclase isoform type V, cAMP formation, and renin release from juxtaglomerular cells. We hypothesized that calcium-sensing receptors are expressed in juxtaglomerular cells and mediate changes in intracellular calcium and renin release. To test this we used primary cultures of isolated mouse juxtaglomerular cells in which we ran RT-PCR, Western blots, and immunofluorescence. RT-PCR showed a positive band at the expected 151 bp consistent with calcium-sensing receptor. Western blots showed a 130- to 150-kDa band confirming the calcium-sensing receptor in juxtaglomerular cells. Immunofluorescence and confocal microscopy using 2 different antibodies against the calcium-sensing receptor in juxtaglomerular cells showed positive fluorescence in the juxtaglomerular cells, which also had positive labeling for renin. To test whether calcium-sensing receptors regulate renin release, juxtaglomerular cells were incubated with a calcium-sensing receptor agonist, the calcimimetic cinacalcet-HCl, at concentrations of 50 and 1000 nmol/L in 0.25 mmol/L of calcium medium. Cinacalcet-HCl decreased juxtaglomerular cell cAMP formation to 47.3+/-6.8% and 44.2+/-9.7% of basal, respectively (P<0.001), and decreased renin release from 541.9+/-86.2 to 364.6+/-64.1 (P<0.05) and 279.6+/-56.9 (P<0.005) ng of angiotensin I per milliliter per hour per milligram of protein, respectively. We conclude that juxtaglomerular cells express the calcium-sensing receptor and that their activation leads to inhibition of adenylyl cyclase-V activity, decreasing cAMP formation and suppressing renin release.
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Affiliation(s)
- M Cecilia Ortiz-Capisano
- Department of Medicine, Hypertension and Vascular Research Division, Henry Ford Hospital, Detroit, MI 48202, USA
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Huang C, Miller RT. Regulation of renal ion transport by the calcium-sensing receptor: an update. Curr Opin Nephrol Hypertens 2007; 16:437-43. [PMID: 17693759 DOI: 10.1097/mnh.0b013e3282b974a6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW Extracellular calcium has profound effects on renal tubular transport, presumably via the calcium-sensing receptor, which is expressed in all nephron segments, but its effects in specific segments and the mechanism of regulation of transport are not fully understood. RECENT FINDINGS Recognition that activating calcium-sensing receptor mutations result in a Bartter-like syndrome demonstrate that the transport effects of extracellular calcium are mediated by the calcium-sensing receptor. Its presence in the gills and solute and water-transporting organs of fish coupled with appropriate calcium-sensing receptor kinetics indicate that the calcium-sensing receptor was originally involved in the regulation of sodium chloride, calcium and magnesium transport. Based on its physiological effects on tubular transport and biochemical and genetic data, the calcium-sensing receptor appears to act by mechanisms that distinguish it from other G protein-coupled receptors. SUMMARY The calcium-sensing receptor mediates the effects of extracellular calcium on the kidney, is an essential control point in the regulation of calcium balance and possibly the physiological regulation of sodium chloride balance. The thick ascending limb of Henle and distal convoluted tubule appear to be the nephron segments most responsible for the effects of the calcium-sensing receptor, although its mechanisms of action are not fully established.
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Affiliation(s)
- Chunfa Huang
- Department of Medicine, Case-Western Reserve University, Louis Stokes VAMC, Rammelkamp Center for Research, Metrohealth Medical Center, Cleveland, Ohio, USA
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Current World Literature. Curr Opin Nephrol Hypertens 2007; 16:388-93. [PMID: 17565283 DOI: 10.1097/mnh.0b013e3282472fd5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Abstract
PURPOSE OF REVIEW We will describe the pathophysiology of hypercalciuria and the mechanism of the resultant stone formation in a rat model and draw parallels to human hypercalciuria and stone formation. RECENT FINDINGS Through inbreeding we have established a strain of rats that excrete 8-10 times more urinary calcium than control rats. These genetic hypercalciuric rats absorb more dietary calcium at lower 1,25-dihydroxyvitamin D3 levels. Elevated urinary calcium excretion on a low-calcium diet indicated a defect in renal calcium reabsorption and/or an increase in bone resorption. Bone from hypercalciuric rats released more calcium when exposed to 1,25-dihydroxyvitamin D3. Bisphosphonate significantly reduced urinary calcium excretion in rats fed a low-calcium diet. Clearance studies showed a primary defect in renal calcium reabsorption. The intestine, bone and kidneys of the hypercalciuric rats had increased numbers of vitamin D receptors. When hydroxyproline is added to their diet they form calcium oxalate stones, the most common stone type in humans. Increased numbers of vitamin D receptors may cause hypercalciuria in these rats and humans. SUMMARY Understanding the mechanism of hypercalciuria and stone formation in this animal model will help clinicians devise effective treatment strategies for preventing recurrent stone formation in humans.
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Affiliation(s)
- David A Bushinsky
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine, Rochester, New York 14642, USA.
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Abstract
PURPOSE OF REVIEW In idiopathic hypercalciuria, patients have increased intestinal Ca absorption and decreased renal Ca reabsorption, with either elevated or normal serum levels of 1,25-dihydroxyvitamin D. As 1,25-dihydroxyvitamin D exerts its biologic effects through interactions with the vitamin D receptor, we examine the actions of this receptor and 1,25-dihydroxyvitamin D in animals with genetic hypercalciuria. RECENT FINDINGS In genetic hypercalciuric stone-forming rats intestinal calcium transport is increased and renal calcium reabsorption is reduced, yet serum 1,25-dihydroxyvitamin D levels are normal. Elevated intestinal and kidney vitamin D receptors suggest that increased tissue 1,25-dihydroxyvitamin D-vitamin D receptor complexes enhance 1,25-dihydroxyvitamin D actions on intestine and kidney, and vitamin D-dependent over-expression of renal calcium-sensing receptor alone can decrease tubule calcium reabsorption. In TRPV5-knockout mice, ablation of the renal calcium-influx channel decreases tubular calcium reabsorption, and secondary elevations in 1,25-dihydroxyvitamin D increase intestinal calcium transport. SUMMARY 1,25-Dihydroxyvitamin D or vitamin D receptor may change intestinal and renal epithelial calcium transport simultaneously or calcium-transport changes across renal epithelia may be primary with a vitamin D-mediated secondary increase in intestinal transport. The extent of homology between the animal models and human idiopathic hypercalciuria remains to be determined.
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Affiliation(s)
- Shaochun Bai
- Section of Endocrinology, University of Chicago Pritzker School of Medicine, Chicago, Illinois 60637, USA
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Bushinsky DA, Laplante K, Asplin JR. Effect of cinacalcet on urine calcium excretion and supersaturation in genetic hypercalciuric stone-forming rats. Kidney Int 2006; 69:1586-92. [PMID: 16557225 DOI: 10.1038/sj.ki.5000324] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Idiopathic hypercalciuria is the most common metabolic abnormality in patients with nephrolithiasis. Through successive inbreeding, we have developed a strain of rats whose urine calcium (UCa) excretion is approximately 8-10-fold greater than that of control rats and who spontaneously form kidney stones. We have termed these rats genetic hypercalciuric stone-forming (GHS) rats. The physiology of the hypercalciuria in the GHS rats closely parallels that of man. We have recently shown that the GHS rat kidneys have an increased number of receptors for calcium (CaR) compared to Sprague-Dawley rats, the strain of rats originally bred to develop the GHS rats. Calcimimetics, such as cinacalcet (Cin), increase the sensitivity of the CaR to Ca. The effects of Cin on UCa are complex and difficult to predict. We tested the hypothesis that Cin would alter urinary (U) Ca and supersaturation with respect to calcium hydrogen phosphate (CaHPO(4)) and calcium oxalate (CaOx). GHS or control rats were fed a normal Ca diet (0.6% Ca) for 28 days with Cin (30 mg/kg/24 h) added to the diet of half of each group for the last 14 days. The protocol was then repeated while the rats were fed a low Ca (0.02% Ca) diet. We found that Cin led to a marked reduction in circulating parathyroid hormone and a modest reduction in serum Ca. Cin did not alter UCa when the GHS rats were fed the normal Ca diet but lowered UCa when they were fed the low Ca diet. However, Cin did not alter U supersaturation with respect to either CaOx or CaHPO(4) on either diet. If these findings in GHS rats can be confirmed in man, it suggests that Cin would not be an effective agent in the treatment of human idiopathic hypercalciuria and resultant stone formation.
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Affiliation(s)
- D A Bushinsky
- Nephrology Division, Department of Medicine, University of Rochester School of Medicine, Rochester, New York, USA.
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Bibliography. Current world literature. Mineral metabolism. Curr Opin Nephrol Hypertens 2006; 15:464-7. [PMID: 16775463 DOI: 10.1097/01.mnh.0000232889.65895.ae] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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