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Cui Q, Wang L, Wang H, Chen X, Han L, Geng T, Kou Y, Zhang W, Dai M, Qiao H, Sun Z, Li L, Lan Z, Xu H, Xu J, Dai Y, Geng Y. Nanobodies as negative allosteric modulators for human calcium sensing receptor. Biochem Biophys Res Commun 2024; 695:149401. [PMID: 38154264 DOI: 10.1016/j.bbrc.2023.149401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 12/15/2023] [Accepted: 12/18/2023] [Indexed: 12/30/2023]
Abstract
Human calcium sensing receptor (CaSR) senses calcium ion concentrations in vivo and is an important class of drug targets. Mutations in the receptor can lead to disorders of calcium homeostasis, including hypercalcemia and hypocalcemia. Here, 127 CaSR-targeted nanobodies were generated from camels, and four nanobodies with inhibitory function were further identified. Among these nanobodies, NB32 can effectively inhibit the mobilization of intracellular calcium ions (Ca2+i) and suppress the G12/13 and ERK1/2 signaling pathways downstream of CaSR. Moreover, it enhanced the inhibitory effect of the calcilytics as a negative allosteric modulator (NAM). We determined the structure of complex and found NB32 bound to LB2 (Ligand-binding 2) domain of CaSR to prevent the interaction of LB2 domains of two protomers to stabilize the inactive state of CaSR.
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Affiliation(s)
- Qianqian Cui
- NEST Lab, Department of Chemistry, College of Science, Shanghai University, Shanghai, 200444, China; The CAS Key Laboratory of Receptor Research, Stake Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Lu Wang
- The CAS Key Laboratory of Receptor Research, Stake Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Haonan Wang
- The CAS Key Laboratory of Receptor Research, Stake Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Xiaochen Chen
- The CAS Key Laboratory of Receptor Research, Stake Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Li Han
- The CAS Key Laboratory of Receptor Research, Stake Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Tengjie Geng
- The CAS Key Laboratory of Receptor Research, Stake Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Yongjun Kou
- The CAS Key Laboratory of Receptor Research, Stake Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Wenqing Zhang
- The CAS Key Laboratory of Receptor Research, Stake Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Mei Dai
- The CAS Key Laboratory of Receptor Research, Stake Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Huarui Qiao
- The CAS Key Laboratory of Receptor Research, Stake Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Zengchao Sun
- The CAS Key Laboratory of Receptor Research, Stake Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Lingyun Li
- The CAS Key Laboratory of Receptor Research, Stake Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Zhongyun Lan
- The CAS Key Laboratory of Receptor Research, Stake Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
| | - Hongxi Xu
- School of Pharmacy, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China.
| | - Jiaqiang Xu
- NEST Lab, Department of Chemistry, College of Science, Shanghai University, Shanghai, 200444, China.
| | - Yuanyuan Dai
- Department of Pharmacy, National Cancer Center/ National Clinical Research Center for Cancer/Cancer Hospital, and Peking Union Medical College, Chinese Academy of Medical Science, Beijing, 100021, China.
| | - Yong Geng
- The CAS Key Laboratory of Receptor Research, Stake Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
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Liu G, Li B, Li J, Dong J, Baulin V, Feng Y, Jia D, Petrov YV, Tsivadze AY, Zhou Y. EGTA-Derived Carbon Dots with Bone-Targeting Ability: Target-Oriented Synthesis and Calcium Affinity. ACS APPLIED MATERIALS & INTERFACES 2023; 15:40163-40177. [PMID: 37603390 DOI: 10.1021/acsami.3c05184] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/22/2023]
Abstract
The bone-targeting mechanism of clinic bisphosphonate-type drugs, such as alendronate, risedronate, and ibandronate, relies on chelated calcium ions on the surface of the bone mineralized matrix for the treatment of osteoporosis. EGTA with aminocarboxyl chelating ligands can specifically chelate calcium ions. Inspired by the bone-targeting mechanism of bisphosphonates, we hypothesize that EGTA-derived carbon dots (EGTA-CDs) hold bone-targeting ability. For the target-oriented synthesis of EGTA-CDs and to endow CDs with bone targeting, we designed calcium ion chelating agents as precursors, including aminocarboxyl chelating agents (EGTA and EDTA) and bisphosphonate agents (ALN and HEDP) for the target-oriented synthesis of aminocarboxyl-derived CDs (EGTA-CDs and EDTA-CDs) and bisphosphonate-derived CDs (ALN-CDs and HEDP-CDs) with high synthetic yield. The synthetic yield of EGTA-CDs reached 87.6%. Aminocarboxyl-derived CDs and bisphosphonate-derived CDs retain the chelation ability of calcium ions and can specifically bind calcium ions. The chemical environment bone-targeting value coordination constant K and chelation sites of EGTA-CDs were 6.48 × 104 M-1 and 4.12, respectively. A novel method was established to demonstrate the bone-targeting capability of chelate-functionalized carbon dots using fluorescence quenching in a simulated bone trauma microenvironment. EGTA-CDs exhibit superior bone-targeting ability compared with other aminocarboxyl-derived CDs and bisphosphonate-derived CDs. EGTA-CDs display exceptional specificity toward calcium ions and better bone affinity than ALN-CDs, suggesting their potential as novel bone-targeting drugs. EGTA-CDs with strong calcium ion chelating ability have calcium ion affinity in simulated body fluid and bone-targeting ability in a simulated bone trauma microenvironment. These findings offer new avenues for the development of advanced bone-targeting strategies.
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Affiliation(s)
- Guanxiong Liu
- Institute for Advanced Ceramics, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Baoqiang Li
- Institute for Advanced Ceramics, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150001, P. R. China
- Laboratory of Dynamics and Extreme Characteristics of Promising Nanostructured Materials, Saint Petersburg State University, St. Petersburg 199034, Russia
- MIIT Key Laboratory of Advanced Structural-Functional Integration Materials & Green Manufacturing Technology, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Jie Li
- Institute for Advanced Ceramics, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Jiaxin Dong
- Institute for Advanced Ceramics, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Vladimir Baulin
- Institute of Physiologically Active Compounds, Russian Academy of Sciences, Chernogolovka 142432, Russia
| | - Yujie Feng
- Institute for Advanced Ceramics, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Dechang Jia
- Institute for Advanced Ceramics, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150001, P. R. China
- MIIT Key Laboratory of Advanced Structural-Functional Integration Materials & Green Manufacturing Technology, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Yuri V Petrov
- Laboratory of Dynamics and Extreme Characteristics of Promising Nanostructured Materials, Saint Petersburg State University, St. Petersburg 199034, Russia
| | - Aslan Yu Tsivadze
- Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow 119071, Russia
| | - Yu Zhou
- Institute for Advanced Ceramics, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150001, P. R. China
- MIIT Key Laboratory of Advanced Structural-Functional Integration Materials & Green Manufacturing Technology, Harbin Institute of Technology, Harbin 150001, P. R. China
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Preventing Antibiotic-Resistant Infections: Additively Manufactured Porous Ti6Al4V Biofunctionalized with Ag and Fe Nanoparticles. Int J Mol Sci 2022; 23:ijms232113239. [DOI: 10.3390/ijms232113239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 10/24/2022] [Accepted: 10/28/2022] [Indexed: 11/06/2022] Open
Abstract
Implant-associated infections are highly challenging to treat, particularly with the emergence of multidrug-resistant microbials. Effective preventive action is desired to be at the implant site. Surface biofunctionalization of implants through Ag-doping has demonstrated potent antibacterial results. However, it may adversely affect bone regeneration at high doses. Benefiting from the potential synergistic effects, combining Ag with other antibacterial agents can substantially decrease the required Ag concentration. To date, no study has been performed on immobilizing both Ag and Fe nanoparticles (NPs) on the surface of additively manufactured porous titanium. We additively manufactured porous titanium and biofunctionalized its surface with plasma electrolytic oxidation using a Ca/P-based electrolyte containing Fe NPs, Ag NPs, and the combinations. The specimen’s surface morphology featured porous TiO2 bearing Ag and Fe NPs. During immersion, Ag and Fe ions were released for up to 28 days. Antibacterial assays against methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa showed that the specimens containing Ag NPs and Ag/Fe NPs exhibit bactericidal activity. The Ag and Fe NPs worked synergistically, even when Ag was reduced by up to three times. The biofunctionalized scaffold reduced Ag and Fe NPs, improving preosteoblasts proliferation and Ca-sensing receptor activation. In conclusion, surface biofunctionalization of porous titanium with Ag and Fe NPs is a promising strategy to prevent implant-associated infections and allow bone regeneration and, therefore, should be developed for clinical application.
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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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Santa Maria C, Cheng Z, Li A, Wang J, Shoback D, Tu CL, Chang W. Interplay between CaSR and PTH1R signaling in skeletal development and osteoanabolism. Semin Cell Dev Biol 2016; 49:11-23. [PMID: 26688334 PMCID: PMC4761456 DOI: 10.1016/j.semcdb.2015.12.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 12/05/2015] [Indexed: 12/01/2022]
Abstract
Parathyroid hormone (PTH)-related peptide (PTHrP) controls the pace of pre- and post-natal growth plate development by activating the PTH1R in chondrocytes, while PTH maintains mineral and skeletal homeostasis by modulating calciotropic activities in kidneys, gut, and bone. The extracellular calcium-sensing receptor (CaSR) is a member of family C, G protein-coupled receptor, which regulates mineral and skeletal homeostasis by controlling PTH secretion in parathyroid glands and Ca(2+) excretion in kidneys. Recent studies showed the expression of CaSR in chondrocytes, osteoblasts, and osteoclasts and confirmed its non-redundant roles in modulating the recruitment, proliferation, survival, and differentiation of the cells. This review emphasizes the actions of CaSR and PTH1R signaling responses in cartilage and bone and discusses how these two signaling cascades interact to control growth plate development and maintain skeletal metabolism in physiological and pathological conditions. Lastly, novel therapeutic regimens that exploit interrelationship between the CaSR and PTH1R are proposed to produce more robust osteoanabolism.
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Affiliation(s)
- Christian Santa Maria
- Endocrine Research Unit, University of California, San Francisco, Veterans Affairs Medical Center, San Francisco, CA, USA
| | - Zhiqiang Cheng
- Endocrine Research Unit, University of California, San Francisco, Veterans Affairs Medical Center, San Francisco, CA, USA
| | - Alfred Li
- Endocrine Research Unit, University of California, San Francisco, Veterans Affairs Medical Center, San Francisco, CA, USA
| | - Jiali Wang
- Endocrine Research Unit, University of California, San Francisco, Veterans Affairs Medical Center, San Francisco, CA, USA
| | - Dolores Shoback
- Endocrine Research Unit, University of California, San Francisco, Veterans Affairs Medical Center, San Francisco, CA, USA
| | - Chia-Ling Tu
- Endocrine Research Unit, University of California, San Francisco, Veterans Affairs Medical Center, San Francisco, CA, USA
| | - Wenhan Chang
- Endocrine Research Unit, University of California, San Francisco, Veterans Affairs Medical Center, San Francisco, CA, USA.
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Cianferotti L, Gomes AR, Fabbri S, Tanini A, Brandi ML. The calcium-sensing receptor in bone metabolism: from bench to bedside and back. Osteoporos Int 2015; 26:2055-71. [PMID: 26100412 DOI: 10.1007/s00198-015-3203-1] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 06/08/2015] [Indexed: 12/11/2022]
Abstract
UNLABELLED The calcium-sensing receptor (CaSR), a key player in the maintenance of calcium homeostasis, can influence bone modeling and remodeling by directly acting on bone cells, as demonstrated by in vivo and in vitro evidence. The modulation of CaSR signaling can play a role in bone anabolism. INTRODUCTION The calcium-sensing receptor (CaSR) is a key player in the maintenance of calcium homeostasis through the regulation of PTH secretion and calcium homeostasis, thus indirectly influencing bone metabolism. In addition to this role, in vitro and in vivo evidence points to direct effects of CaSR in bone modeling and remodeling. In addition, the activation of the CaSR is one of the anabolic mechanisms implicated in the action of strontium ranelate, to reduce fracture risk. METHODS This review is based upon the acquisition of data from a PubMed enquiry using the terms "calcium sensing receptor," "CaSR" AND "bone remodeling," "bone modeling," "bone turnover," "osteoblast," "osteoclast," "osteocyte," "chondrocyte," "bone marrow," "calcilytics," "calcimimetics," "strontium," "osteoporosis," "skeletal homeostasis," and "bone metabolism." RESULTS A fully functional CaSR is expressed in osteoblasts and osteoclasts, so that these cells are able to sense changes in the extracellular calcium and as a result modulate their behavior. CaSR agonists (calcimimetics) or antagonists (calcilytics) have the potential to indirectly influence skeletal homeostasis through the modulation of PTH secretion by the parathyroid glands. The bone anabolic effect of strontium ranelate, a divalent cation used as a treatment for postmenopausal and male osteoporosis, might be explained, at least in part, by the activation of CaSR in bone cells. CONCLUSIONS Calcium released in the bone microenvironment during remodeling is a major factor in regulating bone cells. Osteoblast and osteoclast proliferation, differentiation, and apoptosis are influenced by local extracellular calcium concentration. Thus, the calcium-sensing properties of skeletal cells can be exploited in order to modulate bone turnover and can explain the bone anabolic effects of agents developed and employed to revert osteoporosis.
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Affiliation(s)
- L Cianferotti
- Metabolic Bone Diseases Unit, Department of Surgery and Translational Medicine, University of Florence, 50134, Florence, Italy
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Kim JY, Kim N, Yenari MA, Chang W. Hypothermia and pharmacological regimens that prevent overexpression and overactivity of the extracellular calcium-sensing receptor protect neurons against traumatic brain injury. J Neurotrauma 2014; 30:1170-6. [PMID: 23360235 DOI: 10.1089/neu.2012.2691] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Traumatic brain injury (TBI) leads to acute functional deficit in the brain. Molecular events underlying TBI remain unclear. In mouse brains, we found controlled cortical impact (CCI) injury induced overexpression of the extracellular calcium-sensing receptor (CaSR), which is known to stimulate neuronal activity and accumulation of intracellular Ca(2+) and concurrent down-regulation of type B or metabotropic GABA receptor 1 (GABA-B-R1), a prominent inhibitory pathway in the brain. These changes in protein expression preceded and were closely associated with the loss of brain tissue, as indicated by the increased size of cortical cavity at impact sites, and the development of motor deficit, as indicated by the increased frequency of right-biased swing and turn in the CCI mice. Mild hypothermia, an established practice of neuroprotection for brain ischemia, partially but significantly blunted all of the above effects of CCI. Administration of CaSR antagonist NPS89636 mimicked hypothermia to reduce loss of brain tissue and motor functions in the CCI mice. These data together support the concept that CaSR overexpression and overactivity play a causal role in potentiating TBI potentially by stimulating excitatory neuronal responses and by interfering with inhibitory GABA-B-R signaling and that the CaSR could be a novel target for neuroprotection against TBI.
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Affiliation(s)
- Jong Youl Kim
- University of California, San Francisco, California, USA
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Mild Hypothermia Suppresses Calcium-Sensing Receptor (CaSR) Induction Following Forebrain Ischemia While Increasing GABA-B Receptor 1 (GABA-B-R1) Expression. Transl Stroke Res 2013; 2:195-201. [PMID: 21731589 DOI: 10.1007/s12975-011-0082-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Hypothermia improves neurological outcome from cardiac arrest. The mechanisms of protection are multifold, but identifying some may be useful in exploring potential therapeutic targets. The extracellular calcium-sensing receptor (CaSR) was originally found in parathyroid cells in which the receptor senses minute changes in extracellular [Ca(2+)] and promotes Ca(2+) influx and intracellular Ca(2+) release. The CaSR is broadly expressed in the CNS and colocalized with the inhibitory γ-aminobutyric acid-B receptor 1 (GABA-B-R1). In hippocampal neurons, GABA-B-R1 heterodimerizes with CaSR and suppresses CaSR expression. To study the interplay between these two receptors in the development of ischemic cell death and neuroprotection by hypothermia, we subjected C57/BL6 mice to global cerebral ischemia by performing bilateral carotid artery occlusion (10 min) followed by reperfusion for 1-3 days with or without therapeutic hypothermia (33°C for 3 h at the onset of reperfusion). Terminal deoxynucleotidyl transferase dUTP nick end labeling staining and immunohistochemistry showed that forebrain ischemia increased CaSR expression, decreased GABA-B-R1 expression, and promoted cell death. These changes were particularly evident in hippocampal neurons and could be reversed by mild hypothermia. The induction of CaSR, along with reciprocal decreases in GABA-B-R1 expression, may together potentiate ischemic neuronal death, suggesting a new therapeutic target for treatment of ischemic brain injury.
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Terzaki K, Kalloudi E, Mossou E, Mitchell EP, Forsyth VT, Rosseeva E, Simon P, Vamvakaki M, Chatzinikolaidou M, Mitraki A, Farsari M. Mineralized self-assembled peptides on 3D laser-made scaffolds: a new route toward ‘scaffold on scaffold’ hard tissue engineering. Biofabrication 2013; 5:045002. [DOI: 10.1088/1758-5082/5/4/045002] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Kopic S, Geibel JP. Gastric acid, calcium absorption, and their impact on bone health. Physiol Rev 2013; 93:189-268. [PMID: 23303909 DOI: 10.1152/physrev.00015.2012] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Calcium balance is essential for a multitude of physiological processes, ranging from cell signaling to maintenance of bone health. Adequate intestinal absorption of calcium is a major factor for maintaining systemic calcium homeostasis. Recent observations indicate that a reduction of gastric acidity may impair effective calcium uptake through the intestine. This article reviews the physiology of gastric acid secretion, intestinal calcium absorption, and their respective neuroendocrine regulation and explores the physiological basis of a potential link between these individual systems.
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Affiliation(s)
- Sascha Kopic
- Department of Surgery and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut, USA
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Sun X, McLamore E, Kishore V, Fites K, Slipchenko M, Porterfield DM, Akkus O. Mechanical stretch induced calcium efflux from bone matrix stimulates osteoblasts. Bone 2012; 50:581-91. [PMID: 22227434 DOI: 10.1016/j.bone.2011.12.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Revised: 12/01/2011] [Accepted: 12/19/2011] [Indexed: 10/14/2022]
Abstract
The mechanisms by which bone cells sense critically loaded regions of bone are still a matter of ongoing debate. Animal models to investigate response to microdamage involve post mortem immunohistological analysis and do not allow real-time monitoring of cellular response during the emergence of the damage in bone. Most in vitro mechanical stimulation studies are conducted on non-bone substrates, neglecting the damage-related alterations in the pericellular niche and their potential effects on bone cells. The current study reports spontaneous efflux of calcium ions (Ca(2+)) (1.924±0.742 pmol cm(-2)s(-1)) from regions of devitalized bone matrix undergoing post-yield strains, induced by a stress concentrator. When these samples are seeded with MC3T3-E1 osteoblasts, the strain-induced Ca(2+) efflux from bone elicits cell response at the stress concentration site as manifested by activation of intracellular calcium signaling (increase in fluorescence by 52%±27%). This activity is associated with extracellular calcium because the intracellular calcium signaling in response to mechanical loading subsides when experiments are repeated using demineralized bone substrates (increase in fluorescence by 6%±10%). These results imply a novel perspective where bone matrix acts as an intermediary mechanochemical transducer by converting mechanical strain into a chemical signal (pericellular calcium) to which cells respond. Such a mechanism may be responsible for triggering repair at locations of bone matrix undergoing critical deformation levels.
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Affiliation(s)
- Xuanhao Sun
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA.
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Li J, Sun H, Sun D, Yao Y, Yao F, Yao K. Biomimetic multicomponent polysaccharide/nano-hydroxyapatite composites for bone tissue engineering. Carbohydr Polym 2011. [DOI: 10.1016/j.carbpol.2011.04.015] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Messa P, Alfieri C, Brezzi B. Clinical utilization of cinacalcet in hypercalcemic conditions. Expert Opin Drug Metab Toxicol 2011; 7:517-28. [PMID: 21361849 DOI: 10.1517/17425255.2011.562196] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
INTRODUCTION Cinacalcet has recently been introduced as a treatment for secondary hyperparathyroidism in dialysis patients and for parathyroid carcinoma. However, there has been an increasing interest in finding out whether cinacalcet can be used as a treatment for other parathyroid hormone (PTH)-dependent hypercalcemic conditions also. AREAS COVERED The article reports the most relevant recent contributions dealing with calcium sensing receptor (CaSR) physiology as well as cinacalcet pharmacokinetics and pharmacodynamics. It also looks at the different hypercalcemic conditions where the use of cinacalcet has been proposed. This article was researched using clinical trials, case reports and outstanding basic research published in the last 3 years (MEDLINE database up to 31 November 2010). It provides the reader with an insight into the many unaddressed issues regarding cinacalcet that need to be resolved before it can be used in newly proposed fields. EXPERT OPINION Since cinacalcet may not only have an effect on parathyroid CaSR but also on CaSR expressed at bone and renal levels, it can currently only be considered a good alternative to parathyroidectomy in PTH-dependent hypercalcemic conditions when surgical intervention is burdened by a high failure rate or when it can be considered a risky procedure. At present, cinacalcet cannot be considered the first choice treatment in asymptomatic primary hyperparathyroidism or in mild-to-moderate forms of familial hypocalciuric hypocalcemia.
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Affiliation(s)
- Piergiorgio Messa
- Division of Nephrology, Dialysis, and Renal Transplant, Fondazione Ca' Granda-IRCCS, OspedaleMaggiore-Policlinico, v. Commenda 15, 20122 Milano, Italy.
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Huang Y, Zhou Y, Wong HC, Castiblanco A, Chen Y, Brown EM, Yang JJ. Calmodulin regulates Ca2+-sensing receptor-mediated Ca2+ signaling and its cell surface expression. J Biol Chem 2010; 285:35919-31. [PMID: 20826781 DOI: 10.1074/jbc.m110.147918] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The Ca(2+)-sensing receptor (CaSR) is a member of family C of the GPCRs responsible for sensing extracellular Ca(2+) ([Ca(2+)](o)) levels, maintaining extracellular Ca(2+) homeostasis, and transducing Ca(2+) signaling from the extracellular milieu to the intracellular environment. In the present study, we have demonstrated a Ca(2+)-dependent, stoichiometric interaction between CaM and a CaM-binding domain (CaMBD) located within the C terminus of CaSR (residues 871-898). Our studies suggest a wrapping around 1-14-like mode of interaction that involves global conformational changes in both lobes of CaM with concomitant formation of a helical structure in the CaMBD. More importantly, the Ca(2+)-dependent association between CaM and the C terminus of CaSR is critical for maintaining proper responsiveness of intracellular Ca(2+) responses to changes in extracellular Ca(2+) and regulating cell surface expression of the receptor.
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Affiliation(s)
- Yun Huang
- Department of Chemistry, Center for Drug Design and Advanced Biotechnology, Georgia State University, Atlanta, Georgia 30303, USA
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15
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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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16
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Thein-Han W, Misra R. Biomimetic chitosan-nanohydroxyapatite composite scaffolds for bone tissue engineering. Acta Biomater 2009; 5:1182-97. [PMID: 19121983 DOI: 10.1016/j.actbio.2008.11.025] [Citation(s) in RCA: 375] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2008] [Revised: 11/19/2008] [Accepted: 11/19/2008] [Indexed: 11/27/2022]
Abstract
We describe a comparative assessment of the structure-property-process relationship of three-dimensional chitosan-nanohydroxyapatite (nHA) and pure chitosan scaffolds in conjunction with their respective biological response with the aim of advancing our insight into aspects that concern bone tissue engineering. High- and medium-molecular-weight (MW) chitosan scaffolds with 0.5, 1 and 2 wt.% fraction of nHA were fabricated by freezing and lyophilization. The nanocomposites were characterized by a highly porous structure and the pore size (approximately 50 to 120 microm) was in a similar range for the scaffolds with different content of nHA. A combination of X-ray diffraction, Fourier transform infrared spectroscopy and electron microscopy indicated that nHA particles were uniformly dispersed in chitosan matrix and there was a chemical interaction between chitosan and nHA. The compression modulus of hydrated chitosan scaffolds was increased on the addition of 1 wt.% nHA from 6.0 to 9.2 kPa in high-MW scaffold. The water uptake ability of composites decreased with an increase in the amount of nHA, while the water retention ability was similar to pure chitosan scaffold. After 28 days in physiological condition, nanocomposites indicated about 10% lower degree of degradation in comparison to chitosan scaffold. The biological response of pre-osteoblasts (MC 3T3-E1) on nanocomposite scaffolds was superior in terms of improved cell attachment, higher proliferation, and well-spread morphology in relation to chitosan scaffold. In composite scaffolds, cell proliferation was about 1.5 times greater than pure chitosan after 7 days of culture and beyond, as implied by qualitative analysis via fluorescence microscopy and quantitative study through MTT assay. The observations related to well-developed structure morphology, physicochemical properties and superior cytocompatibility suggest that chitosan-nHA porous scaffolds are potential candidate materials for bone regeneration although it is necessary to further enhance the mechanical properties of the nanocomposite.
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17
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Heberlein KR, Straub AC, Isakson BE. The myoendothelial junction: breaking through the matrix? Microcirculation 2009; 16:307-22. [PMID: 19330678 DOI: 10.1080/10739680902744404] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Within the vasculature, specialized cellular extensions from endothelium (and sometimes smooth muscle) protrude through the extracellular matrix where they interact with the opposing cell type. These structures, termed myoendothelial junctions, have been cited as a possible key element in the control of several vascular physiologies and pathologies. This review will discuss observations that have led to a focus on the myoendothelial junction as a cellular integration point in the vasculature for both homeostatic and pathological conditions and as a possible independent signaling entity. We will also highlight the need for novel approaches to studying the myoendothelial junction in order to comprehend the cellular biology associated with this structure.
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Affiliation(s)
- Katherine R Heberlein
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottsville, Virginia 22908, USA
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18
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Affiliation(s)
- Toru Yamaguchi
- Internal Medicine 1, Shimane University Faculty of Medicine, 89-1 Enya-cho, Izumo, Shimane 693-8501, Japan.
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19
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Dvorak MM, Chen TH, Orwoll B, Garvey C, Chang W, Bikle DD, Shoback DM. Constitutive activity of the osteoblast Ca2+-sensing receptor promotes loss of cancellous bone. Endocrinology 2007; 148:3156-63. [PMID: 17412806 DOI: 10.1210/en.2007-0147] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Changes in extracellular [Ca2+] modulate the function of bone cells in vitro via the extracellular Ca2+-sensing receptor (CaR). Within bone microenvironments, resorption increases extracellular [Ca2+] locally. To determine whether enhanced CaR signaling could modulate remodeling and thereby bone mass in vivo, we generated transgenic mice with a constitutively active mutant CaR (Act-CaR) targeted to their mature osteoblasts by the 3.5 kb osteocalcin promoter. Longitudinal microcomputed tomography of cancellous bone revealed reduced bone volume and density, accompanied by a diminished trabecular network, in the Act-CaR mice. The bone loss was secondary to an increased number and activity of osteoclasts, demonstrated by histomorphometry of secondary spongiosa. Histomorphometry, conversely, indicates that bone formation rates were unchanged in the transgenic mice. Constitutive signaling of the CaR in mature osteoblasts resulted in increased expression of RANK-L (receptor activator of nuclear factor-kappaB ligand), the major stimulator of osteoclast differentiation and activation, which is the likely underlying mechanism for the bone loss. The phenotype of Act-CaR mice is not attributable to systemic changes in serum [Ca2+] or PTH levels. We provide the first in vivo evidence that increased signaling by the CaR in mature osteoblasts can enhance bone resorption and further propose that fluctuations in the [Ca2+] within the bone microenvironment may modulate remodeling via the CaR.
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Affiliation(s)
- Melita M Dvorak
- Endocrine Research Unit, Department of Veterans Affairs Medical Center, 4150 Clement Street, University of California, San Francisco, California 94121, USA
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20
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Sendemir-Urkmez A, Jamison RD. The addition of biphasic calcium phosphate to porous chitosan scaffolds enhances bone tissue development in vitro. J Biomed Mater Res A 2007; 81:624-33. [PMID: 17187398 DOI: 10.1002/jbm.a.31010] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Uniform distribution of cells and their extracellular matrix is essential for the in vivo success of bone tissue engineering constructs produced in vitro. In this study, the effects of biphasic calcium phosphate (BCP) granules embedded into chitosan scaffolds on the distribution, morphology, and phenotypic expression of osteoblastic cells were investigated. Mesenchymal stem cells (MSCs) and preosteoblasts were cultured on chitosan scaffolds with and without BCP under osteoblastic differentiation/maturation conditions for periods up to 4 weeks. The addition of 25 wt % BCP to chitosan created a uniform layer of calcium phosphate (CaP) precipitation similar to bone mineral on the scaffold surfaces as determined by scanning electron microscopy and X-ray spectroscopy. Scaffolds with this CaP layer yielded more uniform and complete cell and ECM distribution than chitosan scaffolds without BCP. The suggestion of chemotaxis in the appearance of this response was confirmed by successive experiments in a Boyden chamber. The CaP layer also altered morphology of cells initially attached to the scaffold surfaces, leading to higher expression of marker proteins of osteoblastic phenotype including alkaline phosphatase and osteocalcin. The use of chitosan/BCP scaffolds for culture of MSCs and preosteoblasts enhances bone tissue development in vitro.
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Affiliation(s)
- Aylin Sendemir-Urkmez
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W. Springfield Ave., Urbana, Illinois 61801, USA
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21
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Abstract
A constant extracellular Ca2+ concentration is required for numerous physiological functions at tissue and cellular levels. This suggests that minor changes in Ca2+ will be corrected by appropriate homeostatic systems. The system regulating Ca2+ homeostasis involves several organs and hormones. The former are mainly the kidneys, skeleton, intestine and the parathyroid glands. The latter comprise, amongst others, the parathyroid hormone, vitamin D and calcitonin. Progress has recently been made in the identification and characterisation of Ca2+ transport proteins CaT1 and ECaC and this has provided new insights into the molecular mechanisms of Ca2+ transport in cells. The G-protein coupled calcium-sensing receptor, responsible for the exquisite ability of the parathyroid gland to respond to small changes in serum Ca2+ concentration was discovered about a decade ago. Research has focussed on the molecular mechanisms determining the serum levels of 1,25(OH)2D3, and on the transcriptional activity of the vitamin D receptor. The aim of recent work has been to elucidate the mechanisms and the intracellular signalling pathways by which parathyroid hormone, vitamin D and calcitonin affect Ca2+ homeostasis. This article summarises recent advances in the understanding and the molecular basis of physiological Ca2+ homeostasis.
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Affiliation(s)
- Indra Ramasamy
- Department of Chemical Pathology, Newham University Hospital, London, UK.
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22
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Abstract
Bone is the major sink and store for calcium and it fulfils essential roles in the maintenance of extracellular free ionised calcium concentration ([Ca2+]e) within its homeostatic range (1.1-1.3 mM). In response to acute hypercalcaemia or hypocalcaemia, Ca2+ is rapidly transported into or out of bone. Bone turnover (and therefore bone Ca2+ turnover) achieves the long-term correction of the [Ca2+]e by the metabolic actions of osteoblasts and osteoclasts, as they respectively incorporate or release Ca2+ from bone. These processes are regulated by the actions of hormones, such as parathyroid hormone (PTH), the release of which is a function of the [Ca2+]e, and is regulated by the action of the Ca2+-sensing receptor (CaR) in the parathyroid gland. Tissue culture studies indicate that bone cells also directly respond to increasing and decreasing [Ca2+]e in their vicinity, independently of the systemic factors. Nevertheless, further studies are necessary to identify how the acute and long-term local changes in [Ca2+]e affect bone cells and the physiological processes they are involved in. Also, the molecular mechanisms which enable the bone cells to sense and respond to [Ca2+]e are not clear. Like the parathyroid cells, bone cells also express the CaR, and accumulating evidence indicates the involvement of this receptor in their responses to the changing extracellular ionic environment.
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Affiliation(s)
- Melita M Dvorak
- School of Biological Sciences, G38 Stopford Building, Oxford Road, University of Manchester, Manchester M13 9PT, UK
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23
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Abstract
Extracellular Ca2+-sensing receptors (CaRs) are the molecular basis by which specialized cells detect and respond to changes in the extracellular [Ca2+] ([Ca2+]o). CaRs belong to the family C of G-protein coupled receptors (GPCRs). Activation of CaRs triggers signaling pathways that modify numerous cell functions. Multiple ligands regulate the activation of CaRs including multivalent cations, L-amino acids, and changes in ionic strength and pH. CaRs in parathyroid cells play a central role in systemic Ca2+ homeostasis in terrestrial tetrapods. Mutations of the CaR gene in humans cause diseases in which serum and urine [Ca2+] and parathyroid hormone (PTH) levels are altered. CaR homologues are also expressed in organs critical to Ca2+ transport in ancient and modern fish, suggesting that similar receptors may have long been involved in Ca2+ homeostasis in lower vertebrates before parathyroid glands developed in terrestrial vertebrates. CaR mRNA and protein are also expressed in tissues not directly involved in Ca2+ homeostasis. This implies that there may be other biological roles for CaRs. Studies of CaR-knockout mice confirm the importance of CaRs in the parathyroid gland and kidney. The functions of CaRs in tissues other than kidney and parathyroid gland, however, remain to be elucidated.
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Affiliation(s)
- Wenhan Chang
- Endocrine Research Unit, Department of Medicine, San Francisco Department of Veterans Affairs Medical Center, University of California, San Francisco, CA, USA.
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24
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Välimäki S, Höög A, Larsson C, Farnebo LO, Bränström R. High Extracellular Ca2+ Hyperpolarizes Human Parathyroid Cells via Ca2+-activated K+ Channels. J Biol Chem 2003; 278:49685-90. [PMID: 14522972 DOI: 10.1074/jbc.m310595200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Membrane potential has a major influence on stimulus-secretion coupling in various excitable cells. The role of membrane potential in the regulation of parathyroid hormone secretion is not known. High K+-induced depolarization increases secretion from parathyroid cells. The paradox is that increased extracellular Ca2+, which inhibits secretion, has also been postulated to have a depolarizing effect. In this study, human parathyroid cells from parathyroid adenomas were used in patch clamp studies of K+ channels and membrane potential. Detailed characterization revealed two K+ channels that were strictly dependent of intracellular Ca2+ concentration. At high extracellular Ca2+, a large K+ current was seen, and the cells were hyperpolarized (-50.4 +/- 13.4 mV), whereas lowering of extracellular Ca2+ resulted in a dramatic decrease in K+ current and depolarization of the cells (-0.1 +/- 8.8 mV, p < 0.001). Changes in extracellular Ca2+ did not alter K+ currents when intracellular Ca2+ was clamped, indicating that K+ channels are activated by intracellular Ca2+. The results were concordant in cell-attached, perforated patch, whole-cell and excised membrane patch configurations. These results suggest that [Ca2+]o regulates membrane potential of human parathyroid cells via Ca2+-activated K+ channels and that the membrane potential may be of greater importance for the stimulus-secretion coupling than recognized previously.
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Affiliation(s)
- Stiina Välimäki
- Department of Molecular Medicine, Karolinska Hospital, Karolinska Institutet, SE-171 76 Stockholm, Sweden
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25
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Abstract
Changes in extracellular calcium (Ca(2+)o) concentration ([Ca2+]o) affect kidney function both under basal and hormone-stimulated conditions. The molecular identification of an extracellular Ca(2+)-sensing receptor (CaR) has confirmed a direct role of Ca(2+)o on parathyroid and kidney function (i.e. independent of calciotropic hormones) as a modulator of Ca2+ homeostasis. In addition, evidence accumulated over the last 10 years has shown that CaR is also expressed in regions outside the calcium homeostatic system where its role is largely undefined but seems to be linked to regulation of local ionic homeostasis. The parathyroid and kidney CaRs are 1081 and 1079 amino acids long, respectively, and belong to the type III family of G protein-coupled receptors (GPCRs), which includes other CaRs, metabotropic glutamate receptors and putative vomeronasal organ receptors. For the CaR, its low (millimolar) affinity for Ca2+, its positive cooperativity and its large ion-sensing extracellular domain, indicate that the receptor is more sensitive to changes in net cationic charge rather than to a specific ligand. Mg2+, trivalent cations of the lanthanide series and polyvalent cations such as spermine and aminoglycoside antibiotics can all activate the receptor in vitro with EC50 values in the micromolar range for trivalent and polyvalent cations or in the millimolar range for Ca2+ and Mg2+. In addition to true CaR agonists, CaR sensitivity to Ca(2+)o is also susceptible to allosteric modulation by ionic strength, L-amino acids and by pharmacological agents. This review will address endogenous and exogenous CaR agonists, the role of the receptor in the calcium homeostatic system and some speculation on possible role(s) of the CaR in regions not involved in mineral ion homeostasis.
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26
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Chen YC, Chen SJ, Chang HT, Huang JK, Wang JL, Tseng LL, Chang HJ, Su W, Law YP, Chen WC, Jan CR. Mechanisms of diethylstilbestrol-induced calcium movement in MG63 human osteosarcoma cells. Toxicol Lett 2001; 122:245-53. [PMID: 11489359 DOI: 10.1016/s0378-4274(01)00370-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The effect of the estrogen diethylstilbestrol (DES) on cytosolic free Ca(2+) levels ([Ca(2+)](i)) in MG63 human osteoblasts was explored by using fura-2 as a Ca(2+) indicator. DES at concentrations between 5--20 microM induced an immediate increase in [Ca(2+)](i) in a concentration-dependent manner with an EC(50) of 10 microM. Removing extracellular Ca(2+) reduced the Ca(2+) signal by 70%. Pretreatment with 50 microM La(3+) or 10 microM of nifedipine, verapamil and diltiazem did not change 20 microM DES-induced [Ca(2+)](i) increases. Addition of 3 mM Ca(2+) increased [Ca(2+)](i) in cells pretreated with 20 microM DES in Ca(2+)-free medium. Pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor) to deplete the endoplasmic reticulum Ca(2+) store partly inhibited 20 microM DES-induced Ca(2+) release, but addition of carbonylcyanide m-chlorophenylhydrazone (CCCP; a mitochondrial uncoupler) and thapsigargin together abolished DES-induced Ca(2+) release. Conversely, pretreatment with 20 microM DES abrogated CCCP- and thapsigargin-induced Ca(2+) release. Inhibition of phospholipase C activity with 2 microM U73122 did not alter 20 microM DES-induced Ca2+ release. Another estrogen 17beta-estradiol also increased [Ca(2+)](i) in a concentration-dependent manner with an EC50 of 7 microM. Together, the data indicate that in human osteoblasts, DES increased [Ca(2+)](i) via causing Ca(2+) release from both mitochondria and the endoplasmic reticulum in a phospholipase C-independent manner, and by causing Ca(2+) influx.
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Affiliation(s)
- Y C Chen
- Department of Orthopaedic Surgery, Chang-Gung Memorial General Hospital, Kaohsiung, Taiwan
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27
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Zach D, Windischhofer W, Leis HJ. Endothelin- and sarafotoxin-induced receptor-mediated calcium mobilization in a clonal murine osteoblast-like cell line, MC3T3-E1/B. Bone 2001; 28:595-602. [PMID: 11425647 DOI: 10.1016/s8756-3282(01)00461-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Previous studies have demonstrated that, in osteoblast-like MC3T3-E1 cells, various endothelin peptides and their homologous sarafotoxins generate prostaglandin E(2) (PGE(2)) release through an ET(A) receptor subtype. In this study, biphasic Ca(2+) signals elicited with endothelin (ET)-1, ET-2, ET-3, beta-ET, S6a1, and S6b (ET/S6) were measured by microspectrofluorimetric methods in cell suspensions loaded with Fura-2 acetoxymethylester (Fura-2 AM). Phospholipase C (PLC)-dependent calcium activation mechanisms seem to be involved. We found evidence of Ca(2+) release from thapsigargin-sensitive and non-thapsigargin-sensitive intracellular Ca(2+) stores as well as Ca(2+) transmembrane inflow through multiple voltage-independent and Ni(2+)-sensitive cation channels. Using an ET(A) receptor antagonist, BQ-123, we showed that this receptor was coupled to Ca(2+) mobilization. All agonists tested, except S6c (an ET(B)-receptor-specific agonist) induced receptor desensitization. Our results demonstrate that the ET/S6-induced Ca(2+) signaling pathway is mediated via an ET(A)-receptor subtype in MC3T3-E1/B cells.
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Affiliation(s)
- D Zach
- Department of Biochemical Analysis and Mass Spectrometry, University Children's Hospital, University of Graz, Graz, Austria.
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28
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Yamaguchi T, Chattopadhyay N, Kifor O, Sanders JL, Brown EM. Activation of p42/44 and p38 mitogen-activated protein kinases by extracellular calcium-sensing receptor agonists induces mitogenic responses in the mouse osteoblastic MC3T3-E1 cell line. Biochem Biophys Res Commun 2000; 279:363-8. [PMID: 11118293 DOI: 10.1006/bbrc.2000.3955] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Recently, substantial evidence has accumulated that the G-protein-coupled, extracellular calcium (Ca(2+)(o))-sensing receptor (CaR) is expressed in bone marrow-derived cells, including osteoblasts, stromal cells, monocytes-macrophages, and osteoclast precursor cells. Our previous studies have shown that the mouse osteoblastic MC3T3-E1 cell line also expresses the CaR and exhibits mitogenic responses when exposed to various CaR agonists. In this study, in order to understand the signaling pathway(s) mediating this response, we studied the effects of CaR agonists on the phosphorylation of p42/44 mitogen-activated protein kinase (MAPK) (Erk1/2), p38 MAPK, and c-Jun N-terminal kinase (JNK) in MC3T3-E1 cells. Raising the level of Ca(2+)(o) (4.5 mM) or addition of the polycationic CaR agonists, gadolinium (Gd(3+)) (25 microM), neomycin (300 microM) or spermine (1 mM), each stimulated phosphorylation of both p42/44 and p38 MAPKs, but not JNK, as assessed using phospho-specific antibodies to the respective MAPKs. Furthermore, phosphorylation of p42/44 and p38 MAPK were markedly inhibited by their selective and potent inhibitors, PD98059 (50 microM) and SB203580 (10 microM), respectively. Finally, the two inhibitors suppressed [(3)H]thymidine incorporation into DNA in MC3T3-E1 cells at a normal level of Ca(2+)(o) (1.8 mM) as well as when stimulated by high (4.5 mM) Ca(2+)(o), Gd(3+), or neomycin. Thus, in mouse osteoblastic MC3T3-E1 cells, both the p42/44 and p38 MAPK cascades play pivotal roles in CaR-stimulated mitogenic responses.
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Affiliation(s)
- T Yamaguchi
- Endocrine-Hypertension Division, Brigham and Women's Hospital, Boston, Massachusetts, 02115, USA
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