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Hui Q, Zhao X, Lu P, Liu S, Nyachoti M, O K, Yang C. Molecular distribution and localization of extracellular calcium-sensing receptor (CaSR) and vitamin D receptor (VDR) at three different laying stages in laying hens (Gallus gallus domesticus). Poult Sci 2021; 100:101060. [PMID: 33752067 PMCID: PMC8010884 DOI: 10.1016/j.psj.2021.101060] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Revised: 11/02/2020] [Accepted: 02/11/2021] [Indexed: 01/06/2023] Open
Abstract
The extracellular calcium-sensing receptor (CaSR) and vitamin D receptor (VDR) play important roles in regulating calcium mobilization, calcium absorption, and calcium homeostasis, and they could be potential therapeutic targets to osteoporosis in laying hens. The present study investigated the molecular distribution of CaSR and VDR and the localization of CaSR in the kidney, proventriculus (true stomach), duodenum, jejunum, ileum, colon, cecum, shell gland, and tibia of laying hens at 3 different laying stages (19, 40, and 55 wk). The results showed that the relative mRNA abundance of CaSR in the kidney, ileum, proventriculus, duodenum, and colon was higher (P < 0.05) than the other tissues at 40 and 55 wk. The relative mRNA abundance of CaSR in the tibia was higher (P < 0.05) at 55 wk than at 40 wk. However, there were no significant differences in the relative protein abundance of CaSR among all tested tissues at peak production or in each tissue at the 3 different laying stages (P > 0.05). The relative mRNA abundance of VDR was higher (P < 0.05) in the small intestine (duodenum, jejunum, and ileum) when compared with other tissues at the 3 different laying stages. The relative protein abundance of VDR in the duodenum was higher (P < 0.05) than that in the proventriculus, colon, and cecum. There were no significant differences in the VDR expression among the tested tissues at the 3 different laying stages (P > 0.05). The immunohistochemical results showed that the positive staining was found widely in each tissue. Moreover, different laying stages did not affect the localization of CaSR except for the tibia tissue. In conclusion, similar to VDR, CaSR was widely expressed not only in the gut but also in the tibia and shell gland in laying hens. The expression level of CaSR and VDR in all tested tissues was unchanged at the different laying stages.
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Affiliation(s)
- Qianru Hui
- Department of Animal Science, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - Xiaoya Zhao
- Department of Animal Science, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - Peng Lu
- Department of Animal Science, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - Shangxi Liu
- Department of Animal Science, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - Martin Nyachoti
- Department of Animal Science, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - Karmin O
- Department of Animal Science, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada; CCARM, St. Boniface Hospital Research Centre, Winnipeg, Manitoba R2H 2A6, Canada
| | - Chengbo Yang
- Department of Animal Science, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.
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Gong J, Sun M, Wang S, He J, Wang Y, Qian Y, Liu Y, Dong L, Ma L, Cheng K, Weng W, Yu M, Zhang YS, Wang H. Surface Modification by Divalent Main-Group-Elemental Ions for Improved Bone Remodeling To Instruct Implant Biofabrication. ACS Biomater Sci Eng 2019; 5:3311-3324. [PMID: 33405574 DOI: 10.1021/acsbiomaterials.9b00270] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Jiaxing Gong
- The Affiliated Stomatologic Hospital, School of Medicine, Zhejiang University, 395 Yanan Road, Hangzhou 310003, China
- Division of Engineering in Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, 65 Landsdowne Street, Cambridge, Massachusetts 02139, United States
- Key Laboratory of Oral Biomedical Research of Zhejiang Province, 268 Kaixuan Road, Hangzhou 310029, China
| | - Miao Sun
- The Affiliated Stomatologic Hospital, School of Medicine, Zhejiang University, 395 Yanan Road, Hangzhou 310003, China
- Key Laboratory of Oral Biomedical Research of Zhejiang Province, 268 Kaixuan Road, Hangzhou 310029, China
| | - Shaolong Wang
- The Affiliated Stomatologic Hospital, School of Medicine, Zhejiang University, 395 Yanan Road, Hangzhou 310003, China
- Key Laboratory of Oral Biomedical Research of Zhejiang Province, 268 Kaixuan Road, Hangzhou 310029, China
| | - Jianxiang He
- The Affiliated Stomatologic Hospital, School of Medicine, Zhejiang University, 395 Yanan Road, Hangzhou 310003, China
- Key Laboratory of Oral Biomedical Research of Zhejiang Province, 268 Kaixuan Road, Hangzhou 310029, China
| | - Yu Wang
- The Affiliated Stomatologic Hospital, School of Medicine, Zhejiang University, 395 Yanan Road, Hangzhou 310003, China
- Key Laboratory of Oral Biomedical Research of Zhejiang Province, 268 Kaixuan Road, Hangzhou 310029, China
| | - Ying Qian
- The Affiliated Stomatologic Hospital, School of Medicine, Zhejiang University, 395 Yanan Road, Hangzhou 310003, China
- Key Laboratory of Oral Biomedical Research of Zhejiang Province, 268 Kaixuan Road, Hangzhou 310029, China
| | - Yu Liu
- The Affiliated Stomatologic Hospital, School of Medicine, Zhejiang University, 395 Yanan Road, Hangzhou 310003, China
- Key Laboratory of Oral Biomedical Research of Zhejiang Province, 268 Kaixuan Road, Hangzhou 310029, China
| | - Lingqing Dong
- The Affiliated Stomatologic Hospital, School of Medicine, Zhejiang University, 395 Yanan Road, Hangzhou 310003, China
- Key Laboratory of Oral Biomedical Research of Zhejiang Province, 268 Kaixuan Road, Hangzhou 310029, China
- School of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Zhejiang University, 38 Zheda Road, Hangzhou 310027, China
| | - Liang Ma
- State Key Laboratory of Fluid Power & Mechatronic Systems, School of Mechanical Engineering, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China
| | - Kui Cheng
- School of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Zhejiang University, 38 Zheda Road, Hangzhou 310027, China
| | - Wenjian Weng
- School of Materials Science and Engineering, State Key Laboratory of Silicon Materials, Zhejiang University, 38 Zheda Road, Hangzhou 310027, China
| | - Mengfei Yu
- The Affiliated Stomatologic Hospital, School of Medicine, Zhejiang University, 395 Yanan Road, Hangzhou 310003, China
- Key Laboratory of Oral Biomedical Research of Zhejiang Province, 268 Kaixuan Road, Hangzhou 310029, China
| | - Yu Shrike Zhang
- Division of Engineering in Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, 65 Landsdowne Street, Cambridge, Massachusetts 02139, United States
| | - Huiming Wang
- The Affiliated Stomatologic Hospital, School of Medicine, Zhejiang University, 395 Yanan Road, Hangzhou 310003, China
- Key Laboratory of Oral Biomedical Research of Zhejiang Province, 268 Kaixuan Road, Hangzhou 310029, China
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Campos-Verdes LM, Costa-Silva DR, da Silva-Sampaio JP, Barros-Oliveira MDC, Escórcio-Dourado CS, Martins LM, Sampaio FA, Revoredo C, Alves-Ribeiro FA, da Silva BB. Review of Polymorphism of the Calcium-Sensing Receptor Gene and Breast Cancer Risk. Cancer Invest 2018; 36:1-7. [PMID: 29504802 DOI: 10.1080/07357907.2018.1430817] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Polymorphism of the calcium-sensing receptor gene (CaSR or CaR) has been associated with an increased risk for breast cancer. This receptor plays an important role in calcium homeostasis, and has also been detected in several tissues that are unrelated to calcium metabolism, such as the skin, brain, and breast. The calcium-sensing receptor on cellular level, it regulates cell differentiation, proliferation, cell death, and gene expression. In breast cancer cells, CaSR seems to stimulate secretion of the parathyroid hormone-related protein (PTHrP), which stimulates cellular proliferation. Likewise, some studies have supported not only an association between calcium receptor gene polymorphism and breast cancer risk, but also a higher aggressiveness and unfavorable outcomes in breast cancer, which led us to make a survey in Pubmed on the subject in the last 10 years. Thus, in the literature there is a paucity of studies on the subject and the aim of this review was to show the role of calcium-sensing receptor and its association with breast cancer risk.
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Affiliation(s)
- Larysse Maira Campos-Verdes
- a Postgraduate Program of Health in Sciences , Federal University of Piauí , 2280 Frei Serafim Avenue, Teresina , Piauí , Brazil
| | - Danylo Rafhael Costa-Silva
- b Postgraduate Program of the Northeast Network of Biotechnology (RENORBIO) , Federal University of Piauí , Teresina , Brazil
| | - João Paulo da Silva-Sampaio
- a Postgraduate Program of Health in Sciences , Federal University of Piauí , 2280 Frei Serafim Avenue, Teresina , Piauí , Brazil
| | | | - Carla Solange Escórcio-Dourado
- b Postgraduate Program of the Northeast Network of Biotechnology (RENORBIO) , Federal University of Piauí , Teresina , Brazil
| | - Luana Mota Martins
- b Postgraduate Program of the Northeast Network of Biotechnology (RENORBIO) , Federal University of Piauí , Teresina , Brazil
| | - Fabiane Araújo Sampaio
- b Postgraduate Program of the Northeast Network of Biotechnology (RENORBIO) , Federal University of Piauí , Teresina , Brazil
| | - Camila Revoredo
- b Postgraduate Program of the Northeast Network of Biotechnology (RENORBIO) , Federal University of Piauí , Teresina , Brazil
| | - Francisco Adelton Alves-Ribeiro
- b Postgraduate Program of the Northeast Network of Biotechnology (RENORBIO) , Federal University of Piauí , Teresina , Brazil
| | - Benedito Borges da Silva
- a Postgraduate Program of Health in Sciences , Federal University of Piauí , 2280 Frei Serafim Avenue, Teresina , Piauí , Brazil.,b Postgraduate Program of the Northeast Network of Biotechnology (RENORBIO) , Federal University of Piauí , Teresina , Brazil
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Pharmacokinetics, Biotransformation, and Excretion of [ 14C]Etelcalcetide (AMG 416) Following a Single Microtracer Intravenous Dose in Patients with Chronic Kidney Disease on Hemodialysis. Clin Pharmacokinet 2017; 56:179-192. [PMID: 27517676 PMCID: PMC5247555 DOI: 10.1007/s40262-016-0433-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Etelcalcetide (AMG 416) is a novel synthetic peptide calcium-sensing receptor activator in clinical development as an intravenous calcimimetic for the treatment of secondary hyperparathyroidism in patients with chronic kidney disease (CKD) on hemodialysis. Etelcalcetide is composed of seven d-aminoacids with an l-cysteine linked to a d-cysteine by a disulfide bond. A single intravenous dose of [14C]etelcalcetide (10 mg; 26.3 kBq; 710 nCi) was administered to patients with CKD on hemodialysis to elucidate the pharmacokinetics, biotransformation, and excretion of etelcalcetide in this setting. Blood, dialysate, urine, and feces were collected to characterize the pharmacokinetics, biotransformation product profiles, mass balance, and formation of anti-etelcalcetide antibodies. Accelerator mass spectrometry was necessary to measure the microtracer quantities of C-14 excreted in the large volumes of dialysate and other biomatrices. An estimated 67 % of the [14C]etelcalcetide dose was recovered in dialysate, urine, and feces 176 days after dose administration. Etelcalcetide was primarily cleared by hemodialysis, with approximately 60 % of the administered dose eliminated in dialysate. Minor excretion was observed in urine and feces. Biotransformation resulted from disulfide exchange with endogenous thiols, and preserved the etelcalcetide d-amino acid backbone. Drug-related radioactivity circulated primarily as serum albumin peptide conjugate (SAPC). Following removal of plasma etelcalcetide by hemodialysis, re-equilibration occurred between SAPC and l-cysteine present in blood to partially restore the etelcalcetide plasma concentrations between dialysis sessions. No unanticipated safety signals or anti-etelcalcetide or anti-SAPC antibodies were detected.
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Tourkova IL, Liu L, Sutjarit N, Larrouture QC, Luo J, Robinson LJ, Blair HC. Adrenocorticotropic hormone and 1,25-dihydroxyvitamin D 3 enhance human osteogenesis in vitro by synergistically accelerating the expression of bone-specific genes. J Transl Med 2017; 97:1072-1083. [PMID: 28737765 PMCID: PMC5844701 DOI: 10.1038/labinvest.2017.62] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 04/14/2017] [Accepted: 05/01/2017] [Indexed: 12/16/2022] Open
Abstract
To improve definition of the physical and hormonal support of bone formation, we studied differentiation of human osteoblasts in vitro at varying combinations of ACTH, 1α,25-dihydroxyvitamin D3 (1,25(OH)2D), and extracellular calcium, with and without added cortisol. Bone mineralization, alkaline phosphatase activity, and osteoblast-specific markers RunX2, osterix, and collagen I increased with 10 pM ACTH, 10 nM 1,25(OH)2D, or at 2 mM calcium with important synergistic activity of combinations of any of these stimuli. Signals induced by ACTH at 10-30 min included cAMP, TGF-β, and Erk1/2 phosphorylation. Affymetrix gene expression analysis showed that 2 h treatment of ACTH or 1,25(OH)2D increased the expression of bone regulating and structural mRNAs, including collagen I, biglycan, the vitamin D receptor, and TGF-β. Accelerating expression of these bone-specific genes was confirmed by quantitative PCR. Expression of 1,25(OH)2D 1α-hydroxylase (1α-hydroxylase) increased with 1,25(OH)2D, ACTH, and extracellular calcium from 0.5 to 2 mM. Unlike renal 1α-hydroxylase, in osteoblasts, 1α-hydroxylase activity is independent of parathyroid hormone. In keeping with calcium responsivity, calcium-sensing receptor RNA and protein increased with 10 nM ACTH or 1,25(OH)2D. Inclusion of 200 nM cortisol or 10 nM ACTH in differentiation media blunted osteoblasts alkaline phosphatase response to 1,25(OH)2D and calcium. Our results point to the importance of ACTH in bone maintenance and that extra skeletal (renal) 1,25(OH)2D is required for bone mineralization despite 1α-hydroxylase expression by osteoblasts.
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Affiliation(s)
- Irina L Tourkova
- The Pittsburgh Veterans Affairs Medical Center, Pittsburgh, PA, USA,Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Li Liu
- The Pittsburgh Veterans Affairs Medical Center, Pittsburgh, PA, USA,Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Nareerat Sutjarit
- Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Quitterie C Larrouture
- Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Jianhua Luo
- Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Lisa J Robinson
- Department of Pathology, West Virginia University School of Medicine, Morgantown, WV, USA,Department of Microbiology, Immunology & Cell Biology, West Virginia University School of Medicine, Morgantown, WV, USA
| | - Harry C Blair
- The Pittsburgh Veterans Affairs Medical Center, Pittsburgh, PA, USA,Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
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Harada K, Inoue A, Yamauchi A, Fujii A. [The pharmacological profile and the clinical efficacy of the world's 1st intravenous calcimimetics; etelcalcetide hydrochloride (Parsabiv ®)]. Nihon Yakurigaku Zasshi 2017; 150:98-113. [PMID: 28794306 DOI: 10.1254/fpj.150.98] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
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Protein/amino-acid modulation of bone cell function. BONEKEY REPORTS 2016; 5:827. [PMID: 28149508 PMCID: PMC5238414 DOI: 10.1038/bonekey.2016.58] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 06/24/2016] [Indexed: 01/07/2023]
Abstract
Nutrients (protein, carbohydrates and fats) have traditionally been thought of as fuels simply providing the energy for cellular metabolic activity. According to the classic view, if nutrients are available, then anabolic pathways are activated, and if nutrients are not available, catabolic pathways are activated. However, it is becoming increasingly clear that nutrient effects on bone cells (stem cells, osteoblasts and osteoclasts) are complex, some nutrients promote bone formation, whereas others interfere with bone formation or actually promote bone break down. At an organ level, nutrient intake can suppress bone breakdown and modulate the activity of the calcium/vitamin D/parathyroid hormone axis. At a cellular level, nutrient intake can impact cellular energetics either through a direct mechanism (binding or uptake of the nutrient into the cell) or indirect (by elevating nutrient-related hormones such as insulin, insulin-like growth factor 1 or incretin hormones). It is also becoming clear that within a nutrient class (for example, protein), individual components (that is, amino acids) can have markedly different effects on cell function and impact bone formation. The focus of this review will be on one nutrient class in particular, dietary protein. As the prevalence of inadequate dietary protein intake increases with age, these findings may have translational implications as to the optimal dietary protein content in the setting of age-associated bone loss.
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Wang Y, Duan XQ, Zhao ZT, Zhang XY, Wang H, Liu DW, Li GS, Jing L. Fluoride Affects Calcium Homeostasis by Regulating Parathyroid Hormone, PTH-Related Peptide, and Calcium-Sensing Receptor Expression. Biol Trace Elem Res 2015; 165:159-66. [PMID: 25645361 DOI: 10.1007/s12011-015-0245-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 01/18/2015] [Indexed: 10/24/2022]
Abstract
Parathyroid hormone (PTH), PTH-related peptide (PTHrP), and calcium-sensing receptor (CaSR) play important roles in maintaining calcium homeostasis. Here, we study the effect of fluoride on expression of PTH, PTHrP, and CaSR both in vitro and in vivo. MC3T3-E1 cells and Sprague-Dawley rats were treated with different concentrations of fluoride. Then, the free calcium ion concentration in cell culture supernatant and serum were measured by biochemical analyzer. The expression of PTH, PTHrP, and CaSR was analyzed by qRT-PCR and Western blot. We found that the low dose of fluoride increased ionized calcium (i[Ca(2+)]) and the high dose of fluoride decreased i[Ca(2+)] in cell culture supernatant. The low dose of fluoride inhibited the PTH and PTHrP expression in MC3T3-E1 cells. The high dose of fluoride improved the PTHrP expression in MC3T3-E1 cells. Interestingly, we found that NaF decreased serum i[Ca(2+)] in rats. Fluoride increased CaSR expression at both messenger RNA (mRNA) and protein levels in MC3T3-E1 cells and rats. The expression of PTHrP protein was inhibited by fluoride in rats fed regular diet and was increased by fluoride in rats fed low-calcium diet. Fluoride also increased the expression of PTH, NF-kappaB ligand (RANKL), and osteoprotegerin (OPG) in rats. The ratio of RANKL/OPG in rats fed low-calcium food in presence or absence of fluoride was significantly increased. These results indicated that fluoride might be able to affect calcium homeostasis by regulating PTH, PTHrP, and CaSR.
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Affiliation(s)
- Ying Wang
- The First Hospital, Norman Bethune of Jilin University, Changchun, 130041, People's Republic of China
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XIE RUI, TANG BO, YONG XIN, LUO GANG, YANG SHIMING. Roles of the calcium sensing receptor in digestive physiology and pathophysiology (Review). Int J Oncol 2014; 45:1355-62. [DOI: 10.3892/ijo.2014.2560] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 04/30/2014] [Indexed: 11/06/2022] Open
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Young SH, Rey O, Sinnett-Smith J, Rozengurt E. Intracellular Ca2+ oscillations generated via the Ca2+-sensing receptor are mediated by negative feedback by PKCα at Thr888. Am J Physiol Cell Physiol 2013; 306:C298-306. [PMID: 24336654 DOI: 10.1152/ajpcell.00194.2013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
To clarify the mechanism(s) underlying intracellular Ca(2+) concentration ([Ca(2+)]i) oscillations induced by an elevation in extracellular Ca(2+) concentration ([Ca(2+)]e) via the extracellular Ca(2+)-sensing receptor (CaR), we analyzed the pattern of [Ca(2+)]i response in multiple (2,303) individual HEK-293 cells transfected with the human CaR. An increase in the [Ca(2+)]e from 1.5 to 3 mM produced oscillatory fluctuations in [Ca(2+)]i in 70% of the cell population. To determine the role of PKC in the generation of [Ca(2+)]i oscillations, cells were exposed to increasing concentrations (0.5-5 μM) of the preferential PKC inhibitor Ro-31-8220 before stimulation by extracellular Ca(2+). Ro-31-8220 at 3-5 μM completely eliminated the [Ca(2+)]e-evoked [Ca(2+)]i oscillations and transformed the pattern to a peak and sustained plateau response. Treatment with other broad PKC inhibitors, including GFI or Gö6983, produced an identical response. Similarly, treatment with Ro-31-8220 or GFI eliminated [Ca(2+)]e-evoked [Ca(2+)]i oscillations in colon-derived SW-480 cells expressing the CaR. Treatment with inhibitors targeting classic PKCs, including Gö6976 and Ro-32-0432 as well as small interfering RNA-mediated knockdown of PKCα, strikingly reduced the proportion of cell displaying [Ca(2+)]e-evoked [Ca(2+)]i oscillations. Furthermore, none of the cells analyzed expressing a CaR mutant in which the major PKC phosphorylation site Thr(888) was converted to alanine (CaRT888A) showed [Ca(2+)]i oscillations after CaR activation. Our results show that [Ca(2+)]i oscillations induced by activation of the CaR in response to an increase in extracellular Ca(2+) or exposure to the calcimimetic R-568 result from negative feedback involving PKCα-mediated phosphorylation of the CaR at Thr(888).
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Affiliation(s)
- Steven H Young
- Division of Digestive Diseases, Department of Medicine, Center for Ulcer Research and Education: Digestive Diseases Research Center David Geffen School of Medicine and Molecular Biology Institute, University of California, Los Angeles, California; and
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Caltabiano S, Dollery CT, Hossain M, Kurtinecz MT, Desjardins JP, Favus MJ, Kumar R, Fitzpatrick LA. Characterization of the effect of chronic administration of a calcium-sensing receptor antagonist, ronacaleret, on renal calcium excretion and serum calcium in postmenopausal women. Bone 2013; 56:154-62. [PMID: 23756230 DOI: 10.1016/j.bone.2013.05.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 04/25/2013] [Accepted: 05/30/2013] [Indexed: 10/26/2022]
Abstract
Ronacaleret is an orally-active calcium-sensing receptor (CaSR) antagonist that has the potential for therapeutic utility in the stimulation of PTH release, notably as a bone anabolic agent comparable to recombinant human PTH(1-34) (rhPTH(1-34)). A recent study has shown that, despite the ability to increase circulating PTH levels in postmenopausal women in a dose-dependent manner, minimal effects of ronacaleret on bone mineral density have been observed. Therefore, the purpose of this study was to characterize the PTH profile as well as calcium metabolism parameters as a marker of PTH biological activity following the administration of ronacaleret or rhPTH(1-34). Administration of ronacaleret led to lower peak levels of PTH than were observed with rhPTH(1-34), however, greater total PTH exposure was observed. Further, chronic administration of either agent was associated with increases in urinary calcium excretion and serum calcium levels, with the magnitude of the changes following ronacaleret significantly greater than that for rhPTH(1-34). The greater magnitude of effects observed with ronacaleret is likely due to the greater total PTH exposure, and is potentially reflective of a state comparable to mild hyperparathyroidism. It is not clear whether the administration of all calcilytics would lead to a similar result, or is due to characteristics specific to ronacaleret.
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Cinacalcet attenuates hypercalcemia observed in mice bearing either Rice H-500 Leydig cell or C26-DCT colon tumors. Eur J Pharmacol 2013; 712:8-15. [PMID: 23623934 DOI: 10.1016/j.ejphar.2013.04.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2012] [Revised: 03/27/2013] [Accepted: 04/03/2013] [Indexed: 11/22/2022]
Abstract
Excessive secretion of parathyroid hormone-related protein (PTHrP) by tumors stimulates bone resorption and increases renal tubular reabsorption of calcium, resulting in hypercalcemia of malignancy. We investigated the ability of cinacalcet, an allosteric modulator of the calcium-sensing receptor, to attenuate hypercalcemia by assessing its effects on blood ionized calcium, serum PTHrP, and calcium-sensing receptor mRNA in mice bearing either Rice H-500 Leydig cell or C26-DCT colon tumors. Cinacalcet effectively decreased hypercalcemia in a dose- and enantiomer-dependent manner; furthermore, cinacalcet normalized phosphorus levels, but did not affect serum PTHrP. Ribonuclease protection assay results demonstrated presence of PTHrP receptor, but not calcium-sensing receptor mRNA in C26-DCT tumors. The mechanism by which cinacalcet lowered serum calcium was investigated in parathyroidectomized rats (i.e., without PTH) made hypercalcemic by PTHrP. Cinacalcet attenuated PTHrP-mediated elevations in blood ionized calcium, which were accompanied by increased plasma calcitonin. Taken together these results suggest that the cinacalcet-mediated decrease in serum calcium is not the result of a direct effect on tumor cells, but rather is the result of increased calcitonin release. In summary, cinacalcet effectively reduced tumor-mediated hypercalcemia and corrected hypophosphatemia in mice. Further investigation of cinacalcet for treatment of hypercalcemia of malignancy is warranted.
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Wilhelm-Bals A, Parvex P, Magdelaine C, Girardin E. Successful use of bisphosphonate and calcimimetic in neonatal severe primary hyperparathyroidism. Pediatrics 2012; 129:e812-6. [PMID: 22331334 DOI: 10.1542/peds.2011-0128] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Neonatal primary hyperparathyroidism (NPHT) is associated with an inactivating homozygous mutation of the calcium sensing receptor (CaSR). The CaSR is expressed most abundantly in the parathyroid glands and the kidney and regulates calcium homeostasis through its ability to modulate parathormone secretion and renal calcium reabsorption. NPHT leads to life threatening hypercalcemia, nephrocalcinosis, bone demineralization, and neurologic disabilities. Surgery is the treatment of choice. While waiting for surgery, bisphosphonates offer a good alternative to deal with hypercalcemia. Cinacalcet is a class II calcimimetic that increases CaSR affinity for calcium, leading to parathormone suppression and increased calcium renal excretion. At present, there is little evidence as to whether cinacalcet could improve the function of mutant CaSR in NPHT. We report a case of NPHT, treated successfully with bisphosphonates and cinacalcet after surgery failure. To our knowledge, it is the first time cinacalcet has been used for NPHT.
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Affiliation(s)
- Alexandra Wilhelm-Bals
- Division of Pediatric Nephrology, Department of Pediatrics, Children Hospital, Geneva, Switzerland.
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Rey O, Chang W, Bikle D, Rozengurt N, Young SH, Rozengurt E. Negative cross-talk between calcium-sensing receptor and β-catenin signaling systems in colonic epithelium. J Biol Chem 2011; 287:1158-67. [PMID: 22094462 DOI: 10.1074/jbc.m111.274589] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Here, we examined the role of the extracellular Ca(2+)-sensing receptor (CaSR) in the control of colonic epithelial cell proliferation in vivo and changes in β-catenin triggered by CaSR stimulation in human colonic epithelial cells in vitro. The in vivo studies, using a novel Casr intestinal-specific knock-out mouse, indicate that the genetic ablation of the Casr leads to hyperproliferation of colonic epithelial cells, expansion of the proliferative zone, changes in crypt structure, and enhanced β-catenin nuclear localization. The in vitro results indicate that stimulation of the CaSR, by Ca(2+) or by the calcimimetic R-568, produced a striking and time-dependent decrease in the phosphorylation of β-catenin at Ser-552 and Ser-675, two amino acid residues that promote β-catenin transcriptional activity. The reduced phosphorylation of β-catenin coincided with a decline in its nuclear localization and a marked redistribution to the plasma membrane. Furthermore, CaSR stimulation promoted a down-regulation of β-catenin-mediated transcriptional activation. These studies demonstrate that signaling pathways emanating from the CaSR control colonic epithelial cell proliferation in vivo and suggest that the mechanism involves regulation of β-catenin phosphorylation.
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Affiliation(s)
- Osvaldo Rey
- Unit of Signal Transduction and Gastrointestinal Cancer, Division of Digestive Diseases, Department of Medicine, CURE: Digestive Diseases Research Center, David Geffen School of Medicine, UCLA, Los Angeles, California 90095, USA.
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15
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Fischer DC, Jensen C, Rahn A, Salewski B, Kundt G, D’Haese PC, Haffner D, Behets GJ. Moderate Strontium Loading Induces Rickets in Rats with Mild Chronic Renal Failure. Kidney Blood Press Res 2011; 34:375-81. [DOI: 10.1159/000328329] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Accepted: 04/01/2011] [Indexed: 11/19/2022] Open
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Abstract
Compelling evidence of a cell surface receptor sensitive to extracellular calcium was observed as early as the 1980s and was finally realized in 1993 when the calcium-sensing receptor (CaR) was cloned from bovine parathyroid tissue. Initial studies relating to the CaR focused on its key role in extracellular calcium homeostasis, but as the amount of information about the receptor grew it became evident that it was involved in many biological processes unrelated to calcium homeostasis. The CaR responds to a diverse array of stimuli extending well beyond that merely of calcium, and these stimuli can lead to the initiation of a wide variety of intracellular signaling pathways that in turn are able to regulate a diverse range of biological processes. It has been through the examination of the molecular characteristics of the CaR that we now have an understanding of how this single receptor is able to convert extracellular messages into specific cellular responses. Recent CaR-related reviews have focused on specific aspects of the receptor, generally in the context of the CaR's role in physiology and pathophysiology. This review will provide a comprehensive exploration of the different aspects of the receptor, including its structure, stimuli, signalling, interacting protein partners, and tissue expression patterns, and will relate their impact on the functionality of the CaR from a molecular perspective.
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Affiliation(s)
- Aaron L Magno
- Department of Endocrinology and Diabetes, First Floor, C Block, Sir Charles Gairdner Hospital, Hospital Avenue, Nedlands 6009, Western Australia, Australia
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17
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Rey O, Young SH, Jacamo R, Moyer MP, Rozengurt E. Extracellular calcium sensing receptor stimulation in human colonic epithelial cells induces intracellular calcium oscillations and proliferation inhibition. J Cell Physiol 2010; 225:73-83. [PMID: 20648625 DOI: 10.1002/jcp.22198] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The extracellular Ca(2+)-sensing receptor (CaR) is increasingly implicated in the regulation of multiple cellular functions in the gastrointestinal tract, including secretion, proliferation and differentiation of intestinal epithelial cells. However, the signaling mechanisms involved remain poorly defined. Here we examined signaling pathways activated by the CaR, including Ca(2+) oscillations, in individual human colon epithelial cells. Single cell imaging of colon-derived cells expressing the CaR, including SW-480, HT-29, and NCM-460 cells, shows that stimulation of this receptor by addition of aromatic amino acids or by an elevation of the extracellular Ca(2+) concentration promoted striking intracellular Ca(2+) oscillations. The intracellular calcium oscillations in response to extracellular Ca(2+) were of sinusoidal pattern and mediated by the phospholipase C/diacylglycerol/inositol 1,4,5-trisphosphate pathway as revealed by a biosensor that detects the accumulation of diacylglycerol in the plasma membrane. The intracellular calcium oscillations in response to aromatic amino acids were of transient type, that is, Ca(2+) spikes that returned to baseline levels, and required an intact actin cytoskeleton, a functional Rho, Filamin A and the ion channel TRPC1. Further analysis showed that re-expression and stimulation of the CaR in human epithelial cells derived from normal colon and from colorectal adenocarcinoma inhibits their proliferation. This inhibition was associated with the activation of the signaling pathway that mediates the generation of sinusoidal, but not transient, intracellular Ca(2+) oscillations. Thus, these results indicate that the CaR can function in two signaling modes in human colonic epithelial cells offering a potential link between gastrointestinal responses and food/nutrients uptake and metabolism.
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Affiliation(s)
- Osvaldo Rey
- Unit of Signal Transduction and Gastrointestinal Cancer, Division of Digestive Diseases, Department of Medicine, CURE, Digestive Diseases Research Center, Molecular Biology Institute and Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, University of California at Los Angeles, California 90095-1786, USA.
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Alon US, VandeVoorde RG. Beneficial effect of cinacalcet in a child with familial hypocalciuric hypercalcemia. Pediatr Nephrol 2010; 25:1747-50. [PMID: 20495831 DOI: 10.1007/s00467-010-1547-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 04/01/2010] [Accepted: 04/06/2010] [Indexed: 12/30/2022]
Abstract
We describe a child with familial hypocalciuric hypercalcemia (FHH) in whom the hypercalcemia seemed to interfere with tissue healing after tympanoplasty. Consequently, he was placed on cinacalcet (30 mg/day), changed after 2 weeks to 60 mg/day. The treatment resulted in a decrease in serum parathyroid hormone (PTH) from 148 to 32 pg/mL (normal 7-75) and ionized calcium from 1.48 to 1.23 mmol/L (1.13-1.34), as well as successful healing of the revised surgical scar. Over the 12-month treatment period no complications were noted. We conclude that cinacalcet may be considered a new, and currently the only, tool in treating children with symptomatic FHH.
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Affiliation(s)
- Uri S Alon
- Section of Pediatric Nephrology, Bone and Mineral Disorders Clinic, Children's Mercy Hospitals and Clinics, University of Missouri at Kansas City, 2401 Gillham Road, Kansas City, MI 64108, USA.
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19
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Marie PJ. The calcium-sensing receptor in bone cells: a potential therapeutic target in osteoporosis. Bone 2010; 46:571-6. [PMID: 19660583 DOI: 10.1016/j.bone.2009.07.082] [Citation(s) in RCA: 171] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Revised: 07/27/2009] [Accepted: 07/29/2009] [Indexed: 12/16/2022]
Abstract
Recent progress has been made in our understanding of the functional role of the seven-transmembrane-spanning extracellular calcium-sensing receptor (CaSR) in bone cells. Both in vitro and in vivo data indicate that the CaSR is a physiological regulator of bone cell metabolism. The CaSR regulates the recruitment, differentiation and survival of osteoblasts and osteoclasts through activation of multiple CaSR-mediated intracellular signaling pathways in bone cells. This raises the possibility that the bone CaSR could potentially be targeted by allosteric modulators, either agonists (calcimimetics) or antagonists (calcilytics) to control bone remodeling. The therapeutic potential of CaSR agonists or antagonists in bone cells is however hampered by their effects on the CaSR in nonskeletal tissues. Rather, direct targeting of the bone CaSR may be of potential interest for the treatment of bone diseases. Targeting the bone CaSR using a bone-seeking CaSR agonist offers a potential mean to modulate bone cell metabolism. The development of drugs that preferentially target the CaSR and possibly other cation-sensing receptors in bone cells may thus be helpful for the treatment of osteoporosis.
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Mamillapalli R, Wysolmerski J. The calcium-sensing receptor couples to Galpha(s) and regulates PTHrP and ACTH secretion in pituitary cells. J Endocrinol 2010; 204:287-97. [PMID: 20032198 PMCID: PMC3777408 DOI: 10.1677/joe-09-0183] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The calcium-sensing receptor (CaR or CASR as listed in the MGI Database) is a G protein-coupled receptor that binds and signals in response to extracellular calcium and other polycations. It is highly expressed on parathyroid and kidney cells, where it participates in the regulation of systemic calcium homeostasis. It is also expressed on many other cell types and is involved in a wide array of biological functions such as cell growth and differentiation, ion transport, and hormone secretion. It has been described to couple to several different G proteins including Galpha(i/0), Galpha(q/11), and Galpha(12/13). Recently, it has also been shown to stimulate cAMP production by coupling to Galpha(s) in immortalized or malignant breast cells. The CaR is expressed on cells in the anterior pituitary and had previously been described to stimulate cAMP production in these cells. In this report, we examined signaling from the CaR in murine pituitary corticotroph-derived, AtT-20 cells. We found that CaR activation led to the stimulation of cAMP production, and PTH-related protein (PTHrP or PTHLH as listed in the MGI Database) and ACTH secretion from these cells. Furthermore, manipulation of cAMP levels was able to modulate PTHrP and ACTH secretion independent of changes in extracellular calcium. Finally, we demonstrated that the CaR couples to Galpha(s) in AtT-20 cells. Therefore, in pituitary corticotroph-like cells, as in breast cancer cells, the CaR utilizes Galpha(s) and activates cAMP production to stimulate hormone secretion.
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Affiliation(s)
- Ramanaiah Mamillapalli
- Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale University School of Medicine, TAC S131, New Haven, Connecticut 06520-8020, USA
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Turkmen F, Ozdemir A, Sevinc C, Eren PA, Demiral S. Calcium-sensing receptor gene polymorphisms and cardiac valvular calcification in patients with chronic renal failure: a pilot study. Hemodial Int 2009; 13:176-80. [PMID: 19432691 DOI: 10.1111/j.1542-4758.2009.00333.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cardiac valvular calcification (VC) is a frequent finding in chronic hemodialysis patients. In addition to demographic and metabolic factors, genetic susceptibility may also influence the occurrence and severity of these abnormalities and account for interindividual variability among patients. In this report, we studied the relation of calcium-sensing receptor (CaSR) gene polymorphisms to the development of VC in chronic hemodialysis patients. A total of 41 chronic hemodialysis patients (26 male, mean age 47.23 +/- 11.36 years vs. 15 females, mean age 48.13 +/- 14.66 years) undergoing treatment for more than 1 year were evaluated with transthoracic echocardiography. In patients with and without VC, CaSR gene polymorphisms (A990G, C1011G) were investigated by PCR, using allele-specific primers. In randomly chosen subjects, PCR analysis was verified by DNA sequencing. Cardiac valve calcification was detected in 21 patients (51.2%). Five of these patients (12.2%) had mitral valve calcification, 4 (9.75%) had aortic valve calcification, and 12 (29.27%) had both. In patients with VC, the frequency of the A/G genotype was slightly higher than those with no VC with a borderline P value (42.9% vs. 15%, chi(2)=3.840, P=0.050). The frequency of the C/C genotype was similar in patients with and without VC (90.5% vs. 85%, P>0.05). The results of this study are not enough to prove the role of CaSR gene polymorphisms in the development of VC. There is a need for large-scale studies on this topic.
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Affiliation(s)
- Funda Turkmen
- Department of Internal Medicine, Haydarpasa Numune Education and Research Hospital, Istanbul, Turkey
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22
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Arabzadeh A, Troy TC, Turksen K. Insights into the role of the calcium sensing receptor in epidermal differentiation in vivo. Mol Biotechnol 2009; 43:264-72. [PMID: 19578997 DOI: 10.1007/s12033-009-9196-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Accepted: 06/16/2009] [Indexed: 11/25/2022]
Abstract
While the important role of calcium (Ca(++)) signaling is fundamental in epidermal cell physiology, a detailed knowledge of precisely how epidermal cells respond to Ca(++) levels is not clear. Using peptide-specific antibodies that we generated, we set out to evaluate the temporal and spatial distribution pattern of the Ca(++)-sensing receptor (CaSR) during epidermogenesis and to assess its involvement in the mature epidermis (e.g., in acute injury and tumorigenesis). Our data indicate a developmentally regulated expression of CaSR: up-regulation occurs in specific epidermal cells and cell layers in normal development or in response to injury when epidermal cells are induced to undergo commitment and early differentiation events, and down-regulation occurs in terminal differentiation stages. These results provide a new perspective on the role of the CaSR in these processes and describe a novel tool for evaluating Ca(++)-mediated epidermal differentiation.
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Affiliation(s)
- Azadeh Arabzadeh
- Sprott Centre for Stem Cell Research at the Ottawa Hospital Research Institute, Ottawa, ON, K1Y 8L6, Canada
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23
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Mamillapalli R, VanHouten J, Zawalich W, Wysolmerski J. Switching of G-protein usage by the calcium-sensing receptor reverses its effect on parathyroid hormone-related protein secretion in normal versus malignant breast cells. J Biol Chem 2008; 283:24435-47. [PMID: 18621740 PMCID: PMC2528989 DOI: 10.1074/jbc.m801738200] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Revised: 05/26/2008] [Indexed: 12/20/2022] Open
Abstract
The calcium-sensing receptor (CaR) is a G-protein-coupled receptor that signals in response to extracellular calcium and regulates parathyroid hormone secretion. The CaR is also expressed on normal mammary epithelial cells (MMECs), where it has been shown to inhibit secretion of parathyroid hormone-related protein (PTHrP) and participate in the regulation of calcium and bone metabolism during lactation. In contrast to normal breast cells, the CaR has been reported to stimulate PTHrP production by breast cancer cells. In this study, we confirmed that the CaR inhibits PTHrP production by MMECs but stimulates PTHrP production by Comma-D cells (immortalized murine mammary cells) and MCF-7 human breast cancer cells. We found that changes in intracellular cAMP, but not phospholipase C or MAPK signaling, correlated with the opposing effects of the CaR on PTHrP production. Pharmacologic stimulation of cAMP accumulation increased PTHrP production by normal and transformed breast cells. Inhibition of protein kinase A activity mimicked the effects of CaR activation on inhibiting PTHrP secretion by MMECs and blocked the effects of the CaR on stimulating PTHrP production in Comma-D and MCF-7 cells. We found that the CaR coupled to Galphai in MMECs but coupled to Galphas in Comma-D and MCF-7 cells. Thus, the opposing effects of the CaR on PTHrP production are because of alternate G-protein coupling of the receptor in normal versus transformed breast cells. Because PTHrP contributes to hypercalcemia and bone metastases, switching of G-protein usage by the CaR may contribute to the pathogenesis of breast cancer.
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Affiliation(s)
- Ramanaiah Mamillapalli
- Section of Endocrinology and Metabolism,
Department of Internal Medicine, School of Medicine and
School of Nursing, Yale University, New Haven,
Connecticut 06520
| | - Joshua VanHouten
- Section of Endocrinology and Metabolism,
Department of Internal Medicine, School of Medicine and
School of Nursing, Yale University, New Haven,
Connecticut 06520
| | - Walter Zawalich
- Section of Endocrinology and Metabolism,
Department of Internal Medicine, School of Medicine and
School of Nursing, Yale University, New Haven,
Connecticut 06520
| | - John Wysolmerski
- Section of Endocrinology and Metabolism,
Department of Internal Medicine, School of Medicine and
School of Nursing, Yale University, New Haven,
Connecticut 06520
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24
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Abstract
Disorders of mineral metabolism are common in both the office and hospital setting. The diagnosis can be simplified by remembering the target organs involved--intestine, kidney, and bone--and by assessing the presence of kidney disease, levels of parathyroid hormone, and vitamin D status. Although the list of possible causes for these derangements is long, most patients who have hypercalcemia have hyperparathyroidism or malignancy; those who have hypocalcemia, hypophosphatemia, and hypomagnesemia have reduced gastrointestinal absorption, and those who have hyperphosphatemia and hypermagnesemia have increased intake in the setting of kidney disease.
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Affiliation(s)
- Sharon M Moe
- Department of Medicine, Division of Nephrology, Indiana University School of Medicine, 1001 West 10th Street, OPW 526, Indianapolis, IN 46202, USA.
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25
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Goodman WG, Quarles LD. Development and progression of secondary hyperparathyroidism in chronic kidney disease: lessons from molecular genetics. Kidney Int 2008; 74:276-88. [PMID: 17568787 DOI: 10.1038/sj.ki.5002287] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The identification of the calcium-sensing receptor (CaSR) and the clarification of its role as the major regulator of parathyroid gland function have important implications for understanding the pathogenesis and evolution of secondary hyperthyroidism in chronic kidney disease (CKD). Signaling through the CaSR has direct effects on three discrete components of parathyroid gland function, which include parathyroid hormone (PTH) secretion, PTH synthesis, and parathyroid gland hyperplasia. Disturbances in calcium and vitamin D metabolism that arise owing to CKD diminish the level of activation of the CaSR, leading to increases in PTH secretion, PTH synthesis, and parathyroid gland hyperplasia. Each represents a physiological adaptive response by the parathyroid glands to maintain plasma calcium homeostasis. Studies of genetically modified mice indicate that signal transduction via the CaSR is a key determinant of parathyroid cell proliferation and parathyroid gland hyperplasia. Because enlargement of the parathyroid glands has important implications for disease progression and disease severity, it is possible that clinical management strategies that maintain adequate calcium-dependent signaling through the CaSR will ultimately prove useful in diminishing parathyroid gland hyperplasia and in modifying disease progression.
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Affiliation(s)
- William G Goodman
- Division of Nephrology, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
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Affiliation(s)
- Ramesh C. Khanal
- Department of Nutrition and Food Sciences and the Center for Integrated BioSystems, Utah State University, Logan, Utah 84322;
| | - Ilka Nemere
- Department of Nutrition and Food Sciences and the Center for Integrated BioSystems, Utah State University, Logan, Utah 84322;
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Cinacalcet and the prevention of secondary hyperparathyroidism in rats with aldosteronism. Am J Med Sci 2008; 335:105-10. [PMID: 18277117 DOI: 10.1097/maj.0b013e318134f013] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND In rats receiving aldosterone/salt treatment (ALDOST), increased Ca2+ excretion leads to a fall in plasma-ionized Ca2+ and appearance of secondary hyperparathyroidism (SHPT) with parathyroid hormone (PTH)-mediated intracellular Ca2+ overloading inducing oxidative stress in diverse tissues. Parathyroidectomy prevents this scenario. Rats with ALDOST were cotreated with cinacalcet (Cina), a calcimimetic that raises the threshold of the parathyroids' Ca(2+)-sensing receptor. METHODS AND RESULTS We monitored plasma-ionized [Ca2+]o, PTH, and total Ca2+ in heart and peripheral blood mononuclear cells (PBMC), and evidence of oxidative stress in heart, PBMC, and plasma. Cina-treated rats for 4 weeks were compared with 4 weeks of ALDOST alone and with untreated age-/gender-matched controls. In comparison to controls, ALDOST led to a fall (P < 0.05) in Ca2+ (1.16 +/- 0.01 vs 1.03 +/- 0.01 mmol/L), which was not prevented by Cina (1.01 +/- 0.03 mmol/L); a rise (P < 0.05) in plasma PTH (36 +/- 7 vs 134 +/- 19 pg/mL) that was attenuated by Cina (69 +/- 12 pg/mL); increased (P < 0.05) cardiac [Ca2+] (3.92 +/- 0.25 vs 6.78 +/- 0.35 nEq/mg FFDT) and PBMC [Ca2+]i (29.8 +/- 2.3 vs 50.2 +/- 2.3 nmol/L), each of which was prevented with Cina (3.65 +/- 0.10 nEq/mg FFDT and 32.5 +/- 6.0 nmol/L, respectively); increased cardiac MDA (0.56 +/- 0.03 vs 0.94+/-0.07 nmol/mg protein) and PBMC H2O2 production (63.5 +/- 7.5 vs 154.0 +/- 25.2 mcb) and reduced (P < 0.05) plasma alpha1-AP activity (39.8 +/- 0.6 vs 29.6 +/- 1.8 mM), each prevented by Cina (0.66 +/- 0.04 mmol/mg protein, 58.2 +/- 12.7 mcb and 37.0 +/- 1.2 mM, respectively). CONCLUSIONS PTH-mediated intracellular Ca2+ overloading accounts for the induction of oxidative stress in diverse tissues in rats with aldosteronism and which can be prevented by Cina.
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Serum calcium values in term and late-preterm neonates receiving gentamicin. Pediatr Nephrol 2008; 23:569-74. [PMID: 18219496 DOI: 10.1007/s00467-007-0707-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Revised: 11/02/2007] [Accepted: 11/06/2007] [Indexed: 02/03/2023]
Abstract
Since noting an apparent increase in hypocalcemia in neonates receiving gentamicin every 24 h (q 24 h) for > or = 4 days, we have prospectively monitored serum calcium (Ca) values in these patients receiving prolonged gentamicin therapy. This study is a retrospective analysis of those values measured during gentamicin treatment. The study included neonates with gestational age > or = 35 weeks who received > or = 4 days of gentamicin therapy and in whom at least one serum Ca value was measured > or = 47 h after initiation of therapy. Hypocalcemia was defined as a serum Ca level < 8 mg/dl (2 mmol/l). Data were analyzed by Student t-test, chi-square test, and Pearson product moment correlation. There were 1,624 neonates that met the study criteria. Ca was < 8 mg/dl in 241 (15%). Ca < 8 mg/dl was more likely in boys than in girls (16.4% vs 11.8%, P = 0.01) and in neonates < 37 weeks gestational age (GA) than in those > or = 37 weeks GA (23.9% vs 14.1%, P = 0.01). A second Ca value was obtained in 883 neonates (54%); 23.2% of neonates with initial Ca < 8 mg/dl remained hypocalcemic, and 30% of these were receiving oral Ca supplementation. The second Ca value was < 8 mg/dl in eight neonates in whom initial Ca was > or = 8 mg/dl. Hypocalcemia is not uncommon in neonates receiving gentamicin therapy, and it may occur more frequently in boys and late-preterm infants. These data suggest that the monitoring of serum Ca levels should be considered when gentamicin is given > or = 4 days.
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29
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Ahlstrom M, Pekkinen M, Riehle U, Lamberg-Allardt C. Extracellular calcium regulates parathyroid hormone-related peptide expression in osteoblasts and osteoblast progenitor cells. Bone 2008; 42:483-90. [PMID: 18096456 DOI: 10.1016/j.bone.2007.10.025] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2007] [Revised: 10/25/2007] [Accepted: 10/26/2007] [Indexed: 01/24/2023]
Abstract
Parathyroid hormone-related peptide (PTHrP) has been shown to have anabolic effects on bone in women with postmenopausal osteoporosis. On the cellular level PTHrP promotes the recruitment of osteogenic cells and prevents apoptotic death of osteoblasts and osteocytes. The calcium concentration is considerably higher in the vicinity of resorbing osteoclasts than in the plasma. Therefore the osteoblasts are likely to be confronted by elevated extracellular calcium concentrations in the areas of resorptive activity. The present study was designed to assess the possibility that extracellular calcium could regulate PTHrP expression in osteoblastic cells. Adult human mesenchymal stem cells (hMSC) were cultured and differentiated by standard methods. The PTHrP release into the culture media was measured by an immunoradiometric assay and the expression of PTHrP, osteocalcin and Runx2 mRNA was assayed by real-time PCR. Increasing the extracellular calcium from 1 mM to 5 mM for 24 h resulted in a 4-6-fold increase in the PTHrP release. PTHrP mRNA was also increased by elevated calcium levels. The effect of calcium stimulation on PTHrP release could be seen within 60 min of treatment. The extracellular calcium sensing receptor (CaR) agonist neomycin mimicked the effects of calcium and the MEK/MAPK inhibitor PD98059 abolished the effect of calcium and neomycin. High extracellular calcium increased the mineralization of hMSC and the expression of osteocalcin, but this effect was not mimicked by neomycin. Our results show that in hMSC, elevated extracellular calcium levels increases both released PTHrP and PTHrP mRNA expression. The effect of calcium on PTHrP can be mimicked by activation of the CaR and can be diminished by inhibition of the MAPK signalling pathway.
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Affiliation(s)
- Mikael Ahlstrom
- Calcium Research Unit, University of Helsinki, Helsinki, Finland.
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30
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Messa P, Macário F, Yaqoob M, Bouman K, Braun J, von Albertini B, Brink H, Maduell F, Graf H, Frazão JM, Bos WJ, Torregrosa V, Saha H, Reichel H, Wilkie M, Zani VJ, Molemans B, Carter D, Locatelli F. The OPTIMA study: assessing a new cinacalcet (Sensipar/Mimpara) treatment algorithm for secondary hyperparathyroidism. Clin J Am Soc Nephrol 2008; 3:36-45. [PMID: 18178780 DOI: 10.2215/cjn.03591006] [Citation(s) in RCA: 167] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND AND OBJECTIVES Cinacalcet, a novel calcimimetic, targets the calcium-sensing receptor to lower parathyroid hormone (PTH), calcium, and phosphorus levels in dialysis patients with secondary hyperparathyroidism (SHPT). This study compared the efficacy of a cinacalcet-based regimen with unrestricted conventional care (vitamin D and phosphate binders) for achieving the stringent National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) targets for dialysis patients. STUDY DESIGN In this multicenter, open-label study, hemodialysis patients with poorly controlled SHPT were randomized to receive conventional care (n = 184) or a cinacalcet-based regimen (n = 368). Doses of cinacalcet, vitamin D sterols, and phosphate binders were adjusted during a 16-wk dose-optimization phase with the use of algorithms that allowed cinacalcet to be used with adjusted doses of vitamin D. The primary end point was the proportion of patients with mean intact PTH < or =300 pg/ml during a 7-wk efficacy assessment phase. RESULTS A higher proportion of patients receiving the cinacalcet-based regimen versus conventional care achieved the targets for PTH (71% versus 22%, respectively; P < 0.001), Ca x P (77% versus 58%, respectively; P < 0.001), calcium (76% versus 33%, respectively; P < 0.001), phosphorus (63% versus 50%, respectively; P = 0.002), and PTH and Ca x P (59% versus 16%, respectively, P < 0.001), and allowed a 22% reduction in vitamin D dosage in patients receiving vitamin D at baseline. Achievement of targets was greatest in patients with less severe disease (intact PTH range, 300 to 500 pg/ml) and the cinacalcet dose required was lower in these patients (median = 30 mg/d). CONCLUSIONS Compared with conventional therapy, a cinacalcet-based treatment algorithm increased achievement of KDOQI treatment targets in dialysis patients in whom conventional therapy was no longer effective in controlling this disease.
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Affiliation(s)
- Piergiorgio Messa
- Nephrology Division, CROFF Policlinico di Milano, Via Della Commenda, 20122 Milano, Italy.
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31
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Abstract
Abnormalities in bone and mineral metabolism have a significant impact on morbidity and mortality among patients with end-stage renal disease (ESRD). In addition to confounding environmental factors, genetic susceptibility factors may also influence the occurrence and severity of these abnormalities and account for interindividual variability among patients. Indeed, polymorphisms involving genes of the calcium/parathyroid hormone/calcitriol axis have been associated with bone and mineral metabolism abnormalities. This review summarizes studies involving polymorphisms of candidate genes and their effects on the development of complications related to bone and mineral metabolism abnormalities among patients with ESRD.
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Affiliation(s)
- Sehsuvar Erturk
- Department of Nephrology, Ankara University School of Medicine, Ankara, Turkey.
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32
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Abstract
Cinacalcet is a type II calcimimetic approved for treatment of secondary hyperparathyroidism in patients with end-stage renal disease. It is generally well tolerated with the most common side effects being nausea and vomiting. Symptomatic hypocalcemia is rare, and persistent hypocalcemia has not been reported to date. We present a case of a 66-year-old woman on chronic outpatient hemodialysis who was initiated on cinacalcet when her intact parathyroid hormone was 1091 pg/mL (normal 15-75 pg/dL). Two weeks later she developed diffuse muscle twitching. The patient required a 72-hour hospitalization and treatment with a continuous intravenous calcium infusion for symptomatic hypocalcemia. The intact parathyroid hormone level at this time was 176 pg/mL. This case is the first report of cinacalcet-induced prolonged and symptomatic hypocalcemia, closely resembling the hungry bone syndrome described in some patients with secondary hyperparathyroidism following surgical parathyroidectomy.
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Affiliation(s)
- Eric S Lazar
- Department of Medicine, Section of Nephrology, University of Chicago, Chicago, Illinois 60637, USA
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33
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Rey O, Young SH, Papazyan R, Shapiro MS, Rozengurt E. Requirement of the TRPC1 Cation Channel in the Generation of Transient Ca2+ Oscillations by the Calcium-sensing Receptor. J Biol Chem 2006; 281:38730-7. [PMID: 17046820 DOI: 10.1074/jbc.m605956200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The calcium-sensing receptor (CaR) is an allosteric protein that responds to extracellular Ca(2+) ([Ca(2+)](o)) and aromatic amino acids with the production of different patterns of oscillations in intracellular Ca(2+) concentration ([Ca(2+)](i)). An increase in [Ca(2+)](o) stimulates phospholipase C-mediated production of inositol 1,4,5-trisphosphate and causes sinusoidal oscillations in [Ca(2+)](i). Conversely, aromatic amino acid-induced CaR activation does not stimulate phospholipase C but engages an unidentified signaling mechanism that promotes transient oscillations in [Ca(2+)](i). We show here that the [Ca(2+)](i) oscillations stimulated by aromatic amino acids were selectively abolished by TRPC1 down-regulation using either a pool of small inhibitory RNAs (siRNAs) or two different individual siRNAs that targeted different coding regions of TRPC1. Furthermore, [Ca(2+)](i) oscillations stimulated by aromatic amino acids were also abolished by inhibition of TRPC1 function with an antibody that binds the pore region of the channel. We also show that aromatic amino acid-stimulated [Ca(2+)](i) oscillations can be prevented by protein kinase C (PKC) inhibitors or siRNA-mediated PKCalpha down-regulation and impaired by either calmodulin antagonists or by the expression of a dominant-negative calmodulin mutant. We propose a model for the generation of CaR-mediated transient [Ca(2+)](i) oscillations that integrates its stimulation by aromatic amino acids with TRPC1 regulation by PKC and calmodulin.
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Affiliation(s)
- Osvaldo Rey
- Unit of Signal Transduction and Gastrointestinal Cancer, Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine, University of California at Los Angeles, 900 Veteran Avenue, Los Angeles, CA 90095, USA.
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34
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Felsenfeld AJ, Levine BS. Milk alkali syndrome and the dynamics of calcium homeostasis. Clin J Am Soc Nephrol 2006; 1:641-54. [PMID: 17699269 DOI: 10.2215/cjn.01451005] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Arnold J Felsenfeld
- Department of Medicine, VA Greater Los Angeles Healthcare System, 11301 Wilshire Boulevard, Los Angeles, CA 90073, USA.
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35
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Roueff S, Saint Georges M, Chuong VT, Abbassi A, Guédon C, de Vernejoul MC, Ureña Torres P. Looking at calcimimetics impact on hypercalcemia of immobilization: Hypotheses and a case study. Hemodial Int 2006; 10:29-34. [PMID: 16441824 DOI: 10.1111/j.1542-4758.2006.01171.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
For the treatment of secondary hyperparathyroidism (HPTH-II) in dialysis patients and hypercalcemia in patients with parathyroid carcinoma. Calcimimetics are a new class of drugs approved in the European Community and the United States by the Food and Drug Administration that were designed to suppress parathyroid hormone (PTH) levels with a simultaneous reduction in serum calcium and phosphorus levels, and calcium phosphorus product (Ca x P). Hypocalcemia is a frequent finding during the correction phase of the HPTH-II with calcimimetics. By contrast, the appearance of a hypercalcemia has yet to be described. In this paper, we report a case of severe hypercalcemia of immobilization in a 40-year-old hemodialyzed woman treated by cinacalcet HCl for a severe HPTH-II (PTH>1,000 pg/mL). A kidney transplantation recipient 1983 to 1995, she was diagnosed with Charcot-Marie Tooth disease in 1991. She had multiple orthopedic interventions for kidney-related osteoarticular problems probably favored by the kidney graft and the immunosuppressive treatment. While she was receiving the maximum dose of 180 mg/day of cinacalcet HCl and PTH at 443 pg/mL, she needed to be hospitalized for a right hip prothesis. Two weeks after the intervention she developed a symptomatic hypercalcemia of 3.57 mmol/L which was resistant to several measures including lowering the calcium concentration in the dialysate, withdrawing all vitamin D and calcium supplementation and the administration of calcitonin. Her serum calcium level was finally stabilized in the 2.37-2.95 mmol/L by administration of a single intravenous dose of pamidronate. This observation illustrates that the pharmacological activation of the parathyroid CaR and other putative CaR on bone cells by calcimimetics did not protect against the occurrence of hypercalcemia of immobilization favored by a severe HPTH-II in a hemodialysis patient.
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Affiliation(s)
- Stéphane Roueff
- Service de Néphrologie-Dialyse, Hôpital de Saint Maurice, Saint Maurice, France
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36
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Abstract
Drugs for treating primary hyperparathyroidism can be divided into two main groups: (i) antiresorptive drugs that inhibit the increased bone turnover, which can be divided into estrogen-like compounds (estrogen, oral contraceptives and selective estrogen receptor modulators [SERMs]), bisphosphonates and calcitonin; and (ii) drugs that interfere with parathyroid hormone (PTH) secretion (currently only cinacalcet is available). No drugs that interfere with PTH action are currently available. Available studies suggest that all classes of drugs are able to lower serum calcium levels. However, calcitonin does so only temporarily. Estrogen-containing compounds (hormone replacement therapy) may be less attractive because of the potential risk of breast cancer, cardiovascular disease and deep vein thromboembolism. Oral contraceptives have not been shown to be able to prevent fractures in the general population, and no data are available on their effect in women with primary hyperparathyroidism. The only SERM marketed for hyperparathyroidism is raloxifene and this has not been associated with an increased risk of breast cancer and cardiovascular diseases, and has been shown to be able to prevent vertebral fractures in postmenopausal women with osteoporosis. Two small trials suggest that raloxifene may increase bone mineral density (BMD) and decrease serum calcium levels in patients with primary hyperparathyroidism. Bisphosphonates have been shown to decrease serum calcium and increase BMD in patients with primary hyperparathyroidism, but PTH levels may increase. Cinacalcet effectively induces a sustained decrease in serum calcium and PTH for up to 1 year. However, BMD does not seem to increase. No data on hard endpoints such as fractures, kidney stones, cardiovascular disease etc. are available for any of the drugs available for the treatment of primary hyperparathyroidism.
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Affiliation(s)
- Peter Vestergaard
- The Osteoporosis Clinic, Aarhus Amtssygehus, Aarhus University Hospital, Aarhus, Denmark
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Nagano N. Pharmacological and clinical properties of calcimimetics: calcium receptor activators that afford an innovative approach to controlling hyperparathyroidism. Pharmacol Ther 2005; 109:339-65. [PMID: 16102839 DOI: 10.1016/j.pharmthera.2005.06.019] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2005] [Accepted: 06/29/2005] [Indexed: 12/28/2022]
Abstract
Circulating levels of calcium ion (Ca2+) are maintained within a narrow physiological range mainly by the action of parathyroid hormone (PTH) secreted from parathyroid gland (PTG) cells. PTG cells can sense small fluctuations in plasma Ca2+ levels by virtue of a cell surface Ca2+ receptor (CaR) that belongs to the superfamily of G protein-coupled receptors (GPCR). Compounds that activate the CaR and inhibit PTH secretion are termed 'calcimimetics' because they mimic or potentiate the effects of extracellular Ca2+ on PTG cell function. Preclinical studies with NPS R-568, a first generation calcimimetic compound that acts as a positive allosteric modulator of the CaR, have demonstrated that oral administration decreases serum levels of PTH and calcium, with a leftward shift in the set-point for calcium-regulated PTH secretion in normal rats. NPS R-568 also suppresses the elevation of serum PTH levels and PTG hyperplasia and can improve bone mineral density (BMD) and strength in rats with chronic renal insufficiency (CRI). Clinical trials with cinacalcet hydrochloride (cinacalcet), a compound with an improved metabolic profile, have shown that long-term treatment continues to suppress the elevation of serum levels of calcium and PTH in patients with primary hyperparathyroidism (1HPT). Furthermore, clinical trials in patients with uncontrolled secondary hyperparathyroidism (2HPT) have demonstrated that cinacalcet not only lowers serum PTH levels, but also the serum phosphorus and calcium x phosphorus product; these are a hallmark of an increased risk of cardiovascular disease and mortality in dialysis patients with end-stage renal disease. Indeed, cinacalcet has already been approved for marketing in several countries. Calcimimetic compounds like cinacalcet have great potential as an innovative medical approach to manage 1HPT and 2HPT.
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Affiliation(s)
- Nobuo Nagano
- Pharmaceutical Development Laboratories, Kirin Brewery Company, Limited, Takasaki, Gunma, Japan.
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38
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Rey O, Young SH, Yuan J, Slice L, Rozengurt E. Amino acid-stimulated Ca2+ oscillations produced by the Ca2+-sensing receptor are mediated by a phospholipase C/inositol 1,4,5-trisphosphate-independent pathway that requires G12, Rho, filamin-A, and the actin cytoskeleton. J Biol Chem 2005; 280:22875-82. [PMID: 15837785 DOI: 10.1074/jbc.m503455200] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The G protein-coupled Ca(2+)-sensing receptor (CaR) is an allosteric protein that responds to two different agonists, Ca(2+) and aromatic amino acids, with the production of sinusoidal or transient oscillations in intracellular Ca(2+) concentration ([Ca(2+)](i)). Here, we examined whether these differing patterns of [Ca(2+)](i) oscillations produced by the CaR are mediated by separate signal transduction pathways. Using real time imaging of changes in phosphatidylinositol 4,5-biphosphate hydrolysis and generation of inositol 1,4,5-trisphosphate in single cells, we found that stimulation of CaR by an increase in the extracellular Ca(2+) concentration ([Ca(2+)](o)) leads to periodic synthesis of inositol 1,4,5-trisphosphate, whereas l-phenylalanine stimulation of the CaR does not induce any detectable change in the level this second messenger. Furthermore, we identified a novel pathway that mediates transient [Ca(2+)](i) oscillations produced by the CaR in response to l-phenylalanine, which requires the organization of the actin cytoskeleton and involves the small GTPase Rho, heterotrimeric proteins of the G(12) subfamily, the C-terminal region of the CaR, and the scaffolding protein filamin-A. Our model envisages that Ca(2+) or amino acids stabilize unique CaR conformations that favor coupling to different G proteins and subsequent activation of distinct downstream signaling pathways.
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Affiliation(s)
- Osvaldo Rey
- Unit of Signal Transduction and Gastrointestinal Cancer, Division of Digestive Diseases, Department of Medicine, UCLA-CURE Digestive Diseases Research Center, David Geffen School of Medicine, University of California at Los Angeles, 90095, USA
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39
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Nagano N, Nemeth EF. Functional proteins involved in regulation of intracellular Ca(2+) for drug development: the extracellular calcium receptor and an innovative medical approach to control secondary hyperparathyroidism by calcimimetics. J Pharmacol Sci 2005; 97:355-60. [PMID: 15781990 DOI: 10.1254/jphs.fmj04007x6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Circulating levels of calcium ion (Ca(2+)) are maintained within a narrow physiological range mainly by the action of parathyroid hormone (PTH) secreted from parathyroid cells. Parathyroid cells can sense small fluctuations in plasma Ca(2+) levels by virtue of a cell surface Ca(2+) receptor (CaR) that belongs to the superfamily of G-protein-coupled receptors. Calcimimetics are positive allosteric modulators that activate the CaR on parathyroid cells and thereby immediately suppress PTH secretion. Pre-clinical studies with NPS R-568, a first generation calcimimetic compound, have demonstrated that daily oral administration inhibits the elevation of plasma PTH levels and parathyroid gland hyperplasia and ameliorates impaired bone qualities in rats with chronic renal insufficiency. The results of clinical trials with cinacalcet hydrochloride, a second generation calcimimetic compound, have shown that calcimimetics possess lowering effects not only on serum PTH levels but also on serum calcium x phosphorus product levels, a hallmark of an increased risk for cardiovascular death in dialysis patients with end-stage renal disease (ESRD). Thus, calcimimetics have considerable potential as an innovative medical approach to manage secondary hyperparathyroidism associated with ESRD. Indeed, cinacalcet hydrochloride has been approved in several countries and is the first positive allosteric modulator of any G protein-coupled receptor to reach the market.
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Affiliation(s)
- Nobuo Nagano
- Pharmaceutical Development Laboratories, Kirin Brewery Co., Ltd., Gunma.
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40
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Abstract
More than 95% of patients with primary hyperparathyroidism (HPT) will be cured at initial operation by an experienced surgeon. Despite this success rate, persistent and recurrent HPT remain challenging clinical entities. The most cost effective and safest treatment for persistent and recurrent HPT is avoidance by successful first operation. The contributors to treatment failure can be categorized into factors related to the initial surgical procedure, anatomic variability, and the biology of disease. An understanding of the factors that commonly contribute to treatment failure can help prevent persistent and recurrent disease and plays an integral role in planning subsequent surgical approaches. Once a biochemical diagnosis of persistent or recurrent HPT is confirmed, a thorough evaluation of previous operative, pathology, and radiology reports is essential. Localization procedures supplement this information and help direct the reoperative approach. When complementary noninvasive studies, such as ultrasound, sestamibi, and magnetic resonance imaging are negative, equivocal, or discordant, invasive tests (eg, selective venous sampling for parathyroid hormone levels) are warranted. Intraoperative ultrasound and gamma-probe localization are of questionable value, but intraoperative parathyroid hormone assays help facilitate these challenging repeat dissections. Repeat parathyroid exploration is associated with more complications and fewer cures compared to the initial explorations and should only be undertaken by an experienced surgeon in a center that can provide expert preoperative localization, adjunctive intraoperative tools, and cryopreservation of parathyroid tissue when necessary. Although controversy exists regarding indications for reoperative treatment for persistent or recurrent HPT, parathyroidectomy remains the only curative treatment option. Surgery should be considered first-line treatment in most circumstances.
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Affiliation(s)
- Nadine R Caron
- Department of Surgery, University of California San Francisco and UCSF Comprehensive Cancer Center at Mount Zion, 1600 Divisadero Street, Hellman Building, Room C3-47, San Francisco, CA 94143, USA
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