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Glitsch MD. Recent advances in acid sensing by G protein coupled receptors. Pflugers Arch 2024; 476:445-455. [PMID: 38340167 PMCID: PMC11006784 DOI: 10.1007/s00424-024-02919-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 01/30/2024] [Accepted: 01/30/2024] [Indexed: 02/12/2024]
Abstract
Changes in extracellular proton concentrations occur in a variety of tissues over a range of timescales under physiological conditions and also accompany virtually all pathologies, notably cancers, stroke, inflammation and trauma. Proton-activated, G protein coupled receptors are already partially active at physiological extracellular proton concentrations and their activity increases with rising proton concentrations. Their ability to monitor and report changes in extracellular proton concentrations and hence extracellular pH appears to be involved in a variety of processes, and it is likely to mirror and in some cases promote disease progression. Unsurprisingly, therefore, these pH-sensing receptors (pHR) receive increasing attention from researchers working in an expanding range of research areas, from cellular neurophysiology to systemic inflammatory processes. This review is looking at progress made in the field of pHRs over the past few years and also highlights outstanding issues.
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Affiliation(s)
- Maike D Glitsch
- Medical School Hamburg, Am Sandtorkai 1, 20457, Hamburg, Germany.
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2
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Hausmann M, Seuwen K, de Vallière C, Busch M, Ruiz PA, Rogler G. Role of pH-sensing receptors in colitis. Pflugers Arch 2024; 476:611-622. [PMID: 38514581 PMCID: PMC11006753 DOI: 10.1007/s00424-024-02943-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Revised: 03/06/2024] [Accepted: 03/06/2024] [Indexed: 03/23/2024]
Abstract
Low pH in the gut is associated with severe inflammation, fibrosis, and colorectal cancer (CRC) and is a hallmark of active inflammatory bowel disease (IBD). Subsequently, pH-sensing mechanisms are of interest for the understanding of IBD pathophysiology. Tissue hypoxia and acidosis-two contributing factors to disease pathophysiology-are linked to IBD, and understanding their interplay is highly relevant for the development of new therapeutic options. One member of the proton-sensing G protein-coupled receptor (GPCR) family, GPR65 (T-cell death-associated gene 8, TDAG8), was identified as a susceptibility gene for IBD in a large genome-wide association study. In response to acidic extracellular pH, GPR65 induces an anti-inflammatory response, whereas the two other proton-sensing receptors, GPR4 and GPR68 (ovarian cancer G protein-coupled receptor 1, OGR1), mediate pro-inflammatory responses. Here, we review the current knowledge on the role of these proton-sensing receptors in IBD and IBD-associated fibrosis and cancer, as well as colitis-associated cancer (CAC). We also describe emerging small molecule modulators of these receptors as therapeutic opportunities for the treatment of IBD.
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Affiliation(s)
- Martin Hausmann
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, 8091, Zurich, CH, Switzerland.
| | - Klaus Seuwen
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, 8091, Zurich, CH, Switzerland
| | - Cheryl de Vallière
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, 8091, Zurich, CH, Switzerland
| | - Moana Busch
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, 8091, Zurich, CH, Switzerland
| | - Pedro A Ruiz
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, 8091, Zurich, CH, Switzerland
| | - Gerhard Rogler
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, 8091, Zurich, CH, Switzerland
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3
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Luo ZH, Ma JX, Zhang W, Tian AX, Gong SW, Li Y, Lai YX, Ma XL. Alterations in the microenvironment and the effects produced of TRPV5 in osteoporosis. J Transl Med 2023; 21:327. [PMID: 37198647 DOI: 10.1186/s12967-023-04182-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 05/05/2023] [Indexed: 05/19/2023] Open
Abstract
The pathogenesis of osteoporosis involves multiple factors, among which alterations in the bone microenvironment play a crucial role in disrupting normal bone metabolic balance. Transient receptor potential vanilloid 5 (TRPV5), a member of the TRPV family, is an essential determinant of the bone microenvironment, acting at multiple levels to influence its properties. TRPV5 exerts a pivotal influence on bone through the regulation of calcium reabsorption and transportation while also responding to steroid hormones and agonists. Although the metabolic consequences of osteoporosis, such as loss of bone calcium, reduced mineralization capacity, and active osteoclasts, have received significant attention, this review focuses on the changes in the osteoporotic microenvironment and the specific effects of TRPV5 at various levels.
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Affiliation(s)
- Zhi-Heng Luo
- Tianjin Hospital, Tianjin University, Jie Fang Nan Road 406, Tianjin, 300211, People's Republic of China
- Tianjin Key Laboratory of Orthopedic Biomechanics and Medical Engineering, Tianjin Hospital, Tianjin, 300050, People's Republic of China
| | - Jian-Xiong Ma
- Tianjin Hospital, Tianjin University, Jie Fang Nan Road 406, Tianjin, 300211, People's Republic of China
- Tianjin Key Laboratory of Orthopedic Biomechanics and Medical Engineering, Tianjin Hospital, Tianjin, 300050, People's Republic of China
| | - Wei Zhang
- Centre for Translational Medicine Research & Development, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, 1068 Xue Yuan Avenue, Shenzhen University Town, Shenzhen, 518055, Guangdong, People's Republic of China
| | - Ai-Xian Tian
- Tianjin Hospital, Tianjin University, Jie Fang Nan Road 406, Tianjin, 300211, People's Republic of China
- Tianjin Key Laboratory of Orthopedic Biomechanics and Medical Engineering, Tianjin Hospital, Tianjin, 300050, People's Republic of China
| | - Shu-Wei Gong
- Tianjin Hospital, Tianjin University, Jie Fang Nan Road 406, Tianjin, 300211, People's Republic of China
- Tianjin Key Laboratory of Orthopedic Biomechanics and Medical Engineering, Tianjin Hospital, Tianjin, 300050, People's Republic of China
| | - Yan Li
- Tianjin Hospital, Tianjin University, Jie Fang Nan Road 406, Tianjin, 300211, People's Republic of China
- Tianjin Key Laboratory of Orthopedic Biomechanics and Medical Engineering, Tianjin Hospital, Tianjin, 300050, People's Republic of China
| | - Yu-Xiao Lai
- Centre for Translational Medicine Research & Development, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, 1068 Xue Yuan Avenue, Shenzhen University Town, Shenzhen, 518055, Guangdong, People's Republic of China.
| | - Xin-Long Ma
- Tianjin Hospital, Tianjin University, Jie Fang Nan Road 406, Tianjin, 300211, People's Republic of China.
- Tianjin Key Laboratory of Orthopedic Biomechanics and Medical Engineering, Tianjin Hospital, Tianjin, 300050, People's Republic of China.
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4
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Wagner CA, Unwin R, Lopez-Garcia SC, Kleta R, Bockenhauer D, Walsh S. The pathophysiology of distal renal tubular acidosis. Nat Rev Nephrol 2023; 19:384-400. [PMID: 37016093 DOI: 10.1038/s41581-023-00699-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/27/2023] [Indexed: 04/06/2023]
Abstract
The kidneys have a central role in the control of acid-base homeostasis owing to bicarbonate reabsorption and production of ammonia and ammonium in the proximal tubule and active acid secretion along the collecting duct. Impaired acid excretion by the collecting duct system causes distal renal tubular acidosis (dRTA), which is characterized by the failure to acidify urine below pH 5.5. This defect originates from reduced function of acid-secretory type A intercalated cells. Inherited forms of dRTA are caused by variants in SLC4A1, ATP6V1B1, ATP6V0A4, FOXI1, WDR72 and probably in other genes that are yet to be discovered. Inheritance of dRTA follows autosomal-dominant and -recessive patterns. Acquired forms of dRTA are caused by various types of autoimmune diseases or adverse effects of some drugs. Incomplete dRTA is frequently found in patients with and without kidney stone disease. These patients fail to appropriately acidify their urine when challenged, suggesting that incomplete dRTA may represent an intermediate state in the spectrum of the ability to excrete acids. Unrecognized or insufficiently treated dRTA can cause rickets and failure to thrive in children, osteomalacia in adults, nephrolithiasis and nephrocalcinosis. Electrolyte disorders are also often present and poorly controlled dRTA can increase the risk of developing chronic kidney disease.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland.
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK.
| | - Robert Unwin
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
| | - Sergio C Lopez-Garcia
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
- Department of Paediatric Nephrology, Great Ormond Street Hospital for Children, NHS Foundation Trust, London, UK
| | - Robert Kleta
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
| | - Detlef Bockenhauer
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
- Department of Paediatric Nephrology, Great Ormond Street Hospital for Children, NHS Foundation Trust, London, UK
| | - Stephen Walsh
- Department of Renal Medicine, Royal Free Hospital, University College London, London, UK
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5
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The importance of kidney calcium handling in the homeostasis of extracellular fluid calcium. Pflugers Arch 2022; 474:885-900. [PMID: 35842482 DOI: 10.1007/s00424-022-02725-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 06/09/2022] [Accepted: 06/30/2022] [Indexed: 12/13/2022]
Abstract
Extracellular fluid calcium concentration must be maintained within a narrow range in order to sustain many biological functions, encompassing muscle contraction, blood coagulation, and bone and tooth mineralization. Blood calcium value is critically dependent on the ability of the renal tubule to reabsorb the adequate amount of filtered calcium. Tubular calcium reabsorption is carried out by various and complex mechanisms in 3 distinct segments: the proximal tubule, the cortical thick ascending limb of the loop of Henle, and the late distal convoluted/connecting tubule. In addition, calcium reabsorption is tightly controlled by many endocrine, paracrine, and autocrine factors, as well as by non-hormonal factors, in order to adapt the tubular handling of calcium to the metabolic requirements. The present review summarizes the current knowledge of the mechanisms and factors involved in calcium handling by the kidney and, ultimately, in extracellular calcium homeostasis. The review also highlights some of our gaps in understanding that need to be addressed in the future.
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Imenez Silva PH, Câmara NO, Wagner CA. Role of proton-activated G protein-coupled receptors in pathophysiology. Am J Physiol Cell Physiol 2022; 323:C400-C414. [PMID: 35759438 DOI: 10.1152/ajpcell.00114.2022] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Local acidification is a common feature of many disease processes such as inflammation, infarction, or solid tumor growth. Acidic pH is not merely a sequelae of disease but contributes to recruitment and regulation of immune cells, modifies metabolism of parenchymal, immune and tumor cells, modulates fibrosis, vascular permeability, oxygen availability and consumption, invasiveness of tumor cells, and impacts on cell survival. Thus, multiple pH-sensing mechanisms must exist in cells involved in these processes. These pH-sensors play important roles in normal physiology and pathophysiology, and hence might be attractive targets for pharmacological interventions. Among the pH-sensing mechanisms, OGR1 (GPR68), GPR4 (GPR4), and TDAG8 (GPR65) have emerged as important molecules. These G protein-coupled receptors are widely expressed, are upregulated in inflammation and tumors, sense changes in extracellular pH in the range between pH 8 and 6, and are involved in modulating key processes in inflammation, tumor biology, and fibrosis. This review discusses key features of these receptors and highlights important disease states and pathways affected by their activity.
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Affiliation(s)
- Pedro H Imenez Silva
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,National Center of Competence in Research NCCR Kidney.CH, Switzerland
| | - Niels Olsen Câmara
- Department of Immunology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,National Center of Competence in Research NCCR Kidney.CH, Switzerland
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7
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Imenez Silva PH, Mohebbi N. Kidney metabolism and acid-base control: back to the basics. Pflugers Arch 2022; 474:919-934. [PMID: 35513635 PMCID: PMC9338915 DOI: 10.1007/s00424-022-02696-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 04/27/2022] [Accepted: 04/28/2022] [Indexed: 01/18/2023]
Abstract
Kidneys are central in the regulation of multiple physiological functions, such as removal of metabolic wastes and toxins, maintenance of electrolyte and fluid balance, and control of pH homeostasis. In addition, kidneys participate in systemic gluconeogenesis and in the production or activation of hormones. Acid-base conditions influence all these functions concomitantly. Healthy kidneys properly coordinate a series of physiological responses in the face of acute and chronic acid-base disorders. However, injured kidneys have a reduced capacity to adapt to such challenges. Chronic kidney disease patients are an example of individuals typically exposed to chronic and progressive metabolic acidosis. Their organisms undergo a series of alterations that brake large detrimental changes in the homeostasis of several parameters, but these alterations may also operate as further drivers of kidney damage. Acid-base disorders lead not only to changes in mechanisms involved in acid-base balance maintenance, but they also affect multiple other mechanisms tightly wired to it. In this review article, we explore the basic renal activities involved in the maintenance of acid-base balance and show how they are interconnected to cell energy metabolism and other important intracellular activities. These intertwined relationships have been investigated for more than a century, but a modern conceptual organization of these events is lacking. We propose that pH homeostasis indissociably interacts with central pathways that drive progression of chronic kidney disease, such as inflammation and metabolism, independent of etiology.
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Affiliation(s)
- Pedro Henrique Imenez Silva
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
- National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland.
| | - Nilufar Mohebbi
- National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
- Praxis Und Dialysezentrum Zurich, Zurich, Switzerland
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8
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Alkali therapy protects renal function, suppresses inflammation, and improves cellular metabolism in kidney disease. Clin Sci (Lond) 2022; 136:557-577. [PMID: 35389462 DOI: 10.1042/cs20220095] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 03/24/2022] [Accepted: 04/07/2022] [Indexed: 11/17/2022]
Abstract
Chronic kidney disease (CKD) affects about 10-13 % of the population worldwide and halting its progression is a major clinical challenge. Metabolic acidosis is both a consequence and a possible driver of CKD progression. Alkali therapy counteracts these effects in CKD patients, but underlying mechanisms remain incompletely understood. Here we show that bicarbonate supplementation protected renal function in a murine CKD model induced by an oxalate-rich diet. Alkali therapy had no effect on the aldosterone-endothelin axis but promoted levels of the anti-aging protein klotho; moreover, it suppressed adhesion molecules required for immune cell invasion along with reducing T helper cell and inflammatory monocyte invasion. Comparing transcriptomes from the murine crystallopathy model and from human biopsies of kidney transplant recipients suffering from acidosis with or without alkali therapy unveils parallel transcriptome responses mainly associated with lipid metabolism and oxidoreductase activity. Our data reveal novel pathways associated with acidosis in kidney disease and sensitive to alkali therapy and identifies potential targets through which alkali therapy may act on CKD and that may be amenable for more targeted therapies.
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9
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Imenez Silva PH, Wagner CA. Physiological relevance of proton-activated GPCRs. Pflugers Arch 2022; 474:487-504. [PMID: 35247105 PMCID: PMC8993716 DOI: 10.1007/s00424-022-02671-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 02/07/2022] [Accepted: 02/08/2022] [Indexed: 12/12/2022]
Abstract
The detection of H+ concentration variations in the extracellular milieu is accomplished by a series of specialized and non-specialized pH-sensing mechanisms. The proton-activated G protein–coupled receptors (GPCRs) GPR4 (Gpr4), TDAG8 (Gpr65), and OGR1 (Gpr68) form a subfamily of proteins capable of triggering intracellular signaling in response to alterations in extracellular pH around physiological values, i.e., in the range between pH 7.5 and 6.5. Expression of these receptors is widespread for GPR4 and OGR1 with particularly high levels in endothelial cells and vascular smooth muscle cells, respectively, while expression of TDAG8 appears to be more restricted to the immune compartment. These receptors have been linked to several well-studied pH-dependent physiological activities including central control of respiration, renal adaption to changes in acid–base status, secretion of insulin and peripheral responsiveness to insulin, mechanosensation, and cellular chemotaxis. Their role in pathological processes such as the genesis and progression of several inflammatory diseases (asthma, inflammatory bowel disease), and tumor cell metabolism and invasiveness, is increasingly receiving more attention and makes these receptors novel and interesting targets for therapy. In this review, we cover the role of these receptors in physiological processes and will briefly discuss some implications for disease processes.
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Affiliation(s)
- Pedro H Imenez Silva
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland. .,National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland.
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland. .,National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland.
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10
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Bushinsky DA, Krieger NS. Effects of Acid on Bone. Kidney Int 2022; 101:1160-1170. [DOI: 10.1016/j.kint.2022.02.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 02/25/2022] [Accepted: 02/28/2022] [Indexed: 12/11/2022]
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Gong S, Ma J, Tian A, Lang S, Luo Z, Ma X. Effects and mechanisms of microenvironmental acidosis on osteoclast biology. Biosci Trends 2021; 16:58-72. [PMID: 34732613 DOI: 10.5582/bst.2021.01357] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Due to continuous bone remodeling, the bone tissue is dynamic and constantly being updated. Bone remodeling is precisely regulated by the balance between osteoblast-induced bone formation and osteoclast-induced bone resorption. As a giant multinucleated cell, formation and activities of osteoclasts are regulated by macrophage colony-stimulating factor (M-CSF), receptor activator of nuclear factor-kappaB ligand (RANKL), and by pathological destabilization of the extracellular microenvironment. Microenvironmental acidosis, as the prime candidate, is a driving force of multiple biological activities of osteoclast precursor and osteoclasts. The mechanisms involved in these processes, especially acid-sensitive receptors/channels, are of great precision and complicated. Recently, remarkable progress has been achieved in the field of acid-sensitive mechanisms of osteoclasts. It is important to elucidate the relationship between microenvironmental acidosis and excessive osteoclasts activity, which will help in understanding the pathophysiology of diseases that are associated with excess bone resorption. This review summarizes physiological consequences and in particular, potential mechanisms of osteoclast precursor or osteoclasts in the context of acidosis microenvironments.
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Affiliation(s)
- Shuwei Gong
- Tianjin Key Laboratory of Orthopedic Biomechanics and Medical Engineering, Orthopedic Research Institute, Tianjin Hospital, Tianjin, China.,Department of Orthopedics, Tianjin Hospital, Tianjin, China.,Graduate School, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Jianxiong Ma
- Tianjin Key Laboratory of Orthopedic Biomechanics and Medical Engineering, Orthopedic Research Institute, Tianjin Hospital, Tianjin, China.,Department of Orthopedics, Tianjin Hospital, Tianjin, China
| | - Aixian Tian
- Tianjin Key Laboratory of Orthopedic Biomechanics and Medical Engineering, Orthopedic Research Institute, Tianjin Hospital, Tianjin, China.,Department of Orthopedics, Tianjin Hospital, Tianjin, China
| | - Shuang Lang
- Tianjin Key Laboratory of Orthopedic Biomechanics and Medical Engineering, Orthopedic Research Institute, Tianjin Hospital, Tianjin, China.,Department of Orthopedics, Tianjin Hospital, Tianjin, China.,Graduate School, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Zhiheng Luo
- Tianjin Key Laboratory of Orthopedic Biomechanics and Medical Engineering, Orthopedic Research Institute, Tianjin Hospital, Tianjin, China.,Department of Orthopedics, Tianjin Hospital, Tianjin, China
| | - Xinlong Ma
- Tianjin Key Laboratory of Orthopedic Biomechanics and Medical Engineering, Orthopedic Research Institute, Tianjin Hospital, Tianjin, China.,Department of Orthopedics, Tianjin Hospital, Tianjin, China
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Krieger NS, Bushinsky DA. Metabolic Acidosis Regulates RGS16 and G-protein Signaling in Osteoblasts. Am J Physiol Renal Physiol 2021; 321:F424-F430. [PMID: 34396788 DOI: 10.1152/ajprenal.00166.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chronic metabolic acidosis stimulates cell-mediated net calcium efflux from bone mediated by increased osteoblastic cyclooxygenase 2 (COX2), leading to prostaglandin E2-induced stimulation of RANKL-induced osteoclastic bone resorption. The osteoblastic H+-sensing G-protein coupled receptor (GPCR), OGR1, is activated by acidosis and leads to increased bne resorption. As regulators of G protein signaling (RGS) proteins limit GPCR signaling, we tested whether RGS proteins themselves are regulated by metabolic acidosis. Primary osteoblasts were isolated from neonatal mouse calvariae and incubated in physiological neutral (NTL) or acidic (MET) medium. Cells were collected and RNA extracted for real time PCR analysis with mRNA levels normalized to RPL13a. RGS1, RGS2, RGS3, RGS4, RGS10, RGS11 or RGS18mRNA did not differ between MET and NTL; however by 30' MET decreased RGS16 which persisted for 60' and 3h. Incubation of osteoblasts with the OGR1 inhibitor CuCl2 inhibited the MET induced increase in RGS16 mRNA. Gallein, a specific inhibitor of Gβγ signaling, was used to determine if downstream signaling by the βγ subunit was critical for the response to acidosis. Gallein decreased net Ca efflux from calvariae and COX2 and RANKL gene expression from isolated osteoblasts. These results indicate that regulation of RGS16 plays an important role in modulating the response of the osteoblastic GPCR, OGR1, to metabolic acidosis and subsequent stimulation of osteoclastic bone resorption.
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Affiliation(s)
- Nancy S Krieger
- Division of Nephrology, Department of Medicine, University of Rochester Medical Center, Rochester, NY, United States
| | - David A Bushinsky
- Division of Nephrology, Department of Medicine, University of Rochester Medical Center, Rochester, NY, United States
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13
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Not etched in bone: the role of osteoclast proton-sensing receptors. Kidney Int 2021; 99:542-545. [PMID: 33637200 DOI: 10.1016/j.kint.2020.11.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Revised: 11/19/2020] [Accepted: 11/23/2020] [Indexed: 11/21/2022]
Abstract
The osteoclast proton-sensing receptors may play a role in osteoclastogenesis or bone resorption. The current study by Kreiger et al. found that in female mice, osteoclast-specific deletion of the gene for OGR1 resulted in increased bone mass, which demonstrates that in some situations this receptor is playing a role. However, there are some inconsistencies because the bone resorption was not reduced in their global knockout mice, and the effects are not seen in both genders or by other investigators. More work should be done to better define the role of OGR1 because acidosis is an important cause of bone loss.
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14
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Prouvot J, Pambrun E, Couchoud C, Vigneau C, Roche S, Allot V, Potier J, Francois M, Babici D, Prelipcean C, Moranne O. Low performance of prognostic tools for predicting dialysis in elderly people with advanced CKD. J Nephrol 2021; 34:1201-1213. [PMID: 33394346 DOI: 10.1007/s40620-020-00919-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Accepted: 11/13/2020] [Indexed: 12/23/2022]
Abstract
INTRODUCTION Clinical decision-making about care plans can be difficult for very elderly people with advanced chronic kidney disease (CKD). Current guidelines propose the use of prognostic tools predicting end stage renal disease (ESRD) to assist in a patient-centered shared decision-making approach. Our objective was to evaluate the existing risk model scores predicting ESRD, from data collected for a French prospective multicenter cohort of mainly octogenarians with advanced CKD. METHODS We performed a rapid review to identify the risk model scores predicting ESRD developed from CKD patient cohorts and evaluated them with data from a prospective multicenter French cohort of elderly (> 75 years) patients with advanced CKD (estimated glomerular filtration rate [eGFR] < 20 mL/min/1.75m2), followed up for 5 years. We evaluated these scores (in absolute risk) for discrimination, calibration and the Brier score. For scores using the same time frame, we made a joint calibration curve and compared areas under the curve (AUCs). RESULTS The PSPA cohort included 573 patients; their mean age was 83 years and their median eGFR was 13 mL/min/1.73 m2. At the end of follow-up, 414 had died and 287 had started renal replacement therapy (RRT). Our rapid review found 12 scores that predicted renal replacement therapy. Five were evaluated: the TANGRI 4-variable, DRAWZ, MARKS, GRAMS, and LANDRAY scores. No score performed well in the PSPA cohort: AUCs ranged from 0.57 to 0.65, and Briers scores from 0.18 to 0.25. CONCLUSIONS The low predictiveness for ESRD of the scores tested in a cohort of octogenarian patients with advanced CKD underlines the need to develop new tools for this population.
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Affiliation(s)
- Julien Prouvot
- EA2415, Université de Montpellier, Montpellier, France.,Service de Nephrologie, Dialyse et Apherese, Hôpital Universitaire de Caremeau, Nimes, France
| | - Emilie Pambrun
- Service de Nephrologie, Dialyse et Apherese, Hôpital Universitaire de Caremeau, Nimes, France
| | - Cecile Couchoud
- Registre REIN, Agence de la Biomedecine, Saint-Denis La Plaine, France.,CNRS, UMR 5558, Laboratoire de Biométrie et Biologie Evolutive, Equipe Biostatistique Santé, Villeurbanne, France
| | - Cecile Vigneau
- CHU Pontchaillou, Service de Néphrologie-Dialyse-Transplantation, Université Rennes 1, IRSET 1085, Rennes, France
| | - Sophie Roche
- Service de Néphrologie-Dialyse, CH Macon, Macon, France
| | - Vincent Allot
- CHU Limoges, Service de Néphrologie, Dialyse, Transplantation, Limoges, France
| | - Jerome Potier
- Service de Néphrologie-Dialyse, CH St Brieuc, Saint Brieuc, France
| | - Maud Francois
- CHU Tours, Service de Néphrologie-Dialyse-Transplantation, Tours, France
| | - Daniela Babici
- Hôpital Emile Muller, Service Néphrologie-Dialyse, GHR MSA, Mulhouse, France
| | - Camelia Prelipcean
- Service de Nephrologie, Dialyse et Apherese, Hôpital Universitaire de Caremeau, Nimes, France
| | - Olivier Moranne
- EA2415, Université de Montpellier, Montpellier, France. .,Service de Nephrologie, Dialyse et Apherese, Hôpital Universitaire de Caremeau, Nimes, France.
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Zhang L, Wu HL, Yu HF, Zhou JL. Time spent outside of the hospital, CKD progression, and mortality: a prospective cohort study. Int Urol Nephrol 2021; 53:1659-1663. [PMID: 33386581 DOI: 10.1007/s11255-020-02749-8] [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: 09/13/2020] [Accepted: 12/07/2020] [Indexed: 11/26/2022]
Abstract
PURPOSE Home time-being out of any healthcare facility-has been proposed as a patient-centered outcome. This novel measure has not been investigated in patients with chronic kidney disease (CKD). The aim of this study is to determine whether there was an association between home time and occurrence of end-stage renal disease (ESRD) or all-cause mortality during 1 year of follow-up. METHODS We assembled a prospective cohort of patients with CKD not requiring dialysis at the Nephrology Center of First Affiliated Hospital of Jiaxing University between May 2014 and April 2017 and followed up for 1 year. Home time was calculated as the number of days spent out of a hospital, rehabilitation facility, or skilled nursing facility. Outcomes included progression to ESRD and all-cause mortality. RESULTS Among 943 patients, 882 (93.5%) had complete follow-up through 1 year. Mean home time was 246.9 ± 126.7 days. In regression analysis, several patient characteristics were associated with significantly reduced home time, including diabetes mellitus, cardiovascular disease, and albuminuria. Home time was strongly correlated with time-to-event endpoints of ESRD (τ=0.324) and all-cause mortality (τ=0.785). CONCLUSIONS Home time is significantly reduced for patients with CKD not requiring dialysis and is highly correlated with traditional time-to-event endpoints. Home time serves as a novel, easily calculated, patient-centered outcome that may reflect effect of interventions on future CKD research.
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Affiliation(s)
- Lin Zhang
- Department of Nephrology, Affiliated Hospital of Jiaxing University, 1882 Zhonghuan South Road, Jiaxing, 314000, China
| | - Heng-Lan Wu
- Department of Nephrology, Affiliated Hospital of Jiaxing University, 1882 Zhonghuan South Road, Jiaxing, 314000, China
| | - Hai-Feng Yu
- Department of Nephrology, Affiliated Hospital of Jiaxing University, 1882 Zhonghuan South Road, Jiaxing, 314000, China
| | - Jun-Liang Zhou
- Department of Nephrology, Affiliated Hospital of Jiaxing University, 1882 Zhonghuan South Road, Jiaxing, 314000, China.
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16
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Krieger NS, Chen L, Becker J, Chan MR, Bushinsky DA. Deletion of the proton receptor OGR1 in mouse osteoclasts impairs metabolic acidosis-induced bone resorption. Kidney Int 2020; 99:609-619. [PMID: 33159961 DOI: 10.1016/j.kint.2020.10.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 09/30/2020] [Accepted: 10/09/2020] [Indexed: 01/03/2023]
Abstract
Metabolic acidosis induces osteoclastic bone resorption and inhibits osteoblastic bone formation. Previously we found that mice with a global deletion of the proton receptor OGR1 had increased bone density although both osteoblast and osteoclast activity were increased. To test whether direct effects on osteoclast OGR1 are critical for metabolic acidosis stimulated bone resorption, we generated knockout mice with an osteoclast-specific deletion of OGR1 (knockout mice). We studied bones from three-month old female mice and the differentiated osteoclasts derived from bone marrow of femurs from these knockout and wild type mice. MicroCT demonstrated increased density in tibiae and femurs but not in vertebrae of the knockout mice. Tartrate resistant acid phosphatase staining of tibia indicated a decrease in osteoclast number and surface area/bone surface from knockout compared to wild type mice. Osteoclasts derived from the marrow of knockout mice demonstrated decreased pit formation, osteoclast staining and osteoclast-specific gene expression compared to those from wild type mice. In response to metabolic acidosis, osteoclasts from knockout mice had decreased nuclear translocation of NFATc1, a transcriptional regulator of differentiation, and no increase in size or number compared to osteoclasts from wild type mice. Thus, loss of osteoclast OGR1 decreased both basal and metabolic acidosis-induced osteoclast activity indicating osteoclast OGR1 is important in mediating metabolic acidosis-induced bone resorption. Understanding the role of OGR1 in metabolic acidosis-induced bone resorption will provide insight into bone loss in acidotic patients with chronic kidney disease.
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Affiliation(s)
- Nancy S Krieger
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine, Rochester, New York, USA.
| | - Luojing Chen
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine, Rochester, New York, USA
| | - Jennifer Becker
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine, Rochester, New York, USA
| | - Michaela R Chan
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine, Rochester, New York, USA
| | - David A Bushinsky
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine, Rochester, New York, USA
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Huang XP, Kenakin TP, Gu S, Shoichet BK, Roth BL. Differential Roles of Extracellular Histidine Residues of GPR68 for Proton-Sensing and Allosteric Modulation by Divalent Metal Ions. Biochemistry 2020; 59:3594-3614. [PMID: 32865988 DOI: 10.1021/acs.biochem.0c00576] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
GPR68, an orphan G-protein coupled receptor, senses protons, couples to multiple G-proteins, and is also activated or inhibited by divalent metal ions. It has seven extracellular histidine residues, although it is not clear how these histidine residues play a role in both proton-sensing and metal ion modulation. Here we demonstrate that divalent metal ions are allosteric modulators that can activate or inhibit proton activity in a concentration- and pH-dependent manner. We then show that single histidine mutants have differential and varying degrees of effects on proton-sensing and metal ion modulation. Some histidine residues play dual roles in proton-sensing and metal ion modulation, while others are important in one or the other but not both. Two extracellular disulfide bonds are predicted to constrain histidine residues to be spatially close to each other. Combining histidine mutations leads to reduced proton activity and resistance to metal ion modulation, while breaking the less conserved disulfide bond results in a more severe reduction in proton-sensing over metal modulation. The small-molecule positive allosteric modulators (PAMs) ogerin and lorazepam are not affected by these mutations and remain active at mutants with severely reduced proton activity or are resistant to metal ion modulation. These results suggest GPR68 possesses two independent allosteric modulation systems, one through interaction with divalent metal ions at the extracellular surface and another through small-molecule PAMs in the transmembrane domains. A new GPR68 model is developed to accommodate the findings which could serve as a template for further studies and ligand discovery by virtual ligand docking.
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Affiliation(s)
| | | | - Shuo Gu
- Department of Pharmaceutical Science, University of California, San Francisco, California 94158, United States
| | - Brian K Shoichet
- Department of Pharmaceutical Science, University of California, San Francisco, California 94158, United States
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18
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Dimke H. G protein-coupled pH-sensing receptor OGR1 and metabolic acidosis-induced hypercalciuria. Kidney Int 2020; 97:852-854. [PMID: 32331595 DOI: 10.1016/j.kint.2020.01.031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 12/24/2019] [Accepted: 01/02/2020] [Indexed: 11/26/2022]
Abstract
Nearly a century ago it was discovered that metabolic acidosis promotes hypercalciuria. Studies have described intrarenal and extrarenal mechanisms underlying calcium wasting in acidosis, in part by altering bone metabolism but also by directly inhibiting renal calcium transport. In this issue of Kidney International, Imenez Silva et al. report that ablation of the pH-sensing receptor ovarian cancer G protein-coupled receptor 1 in a murine model led to Na+/H+-exchanger isoform 3 redistribution in the kidney and dampens the hypercalciuric response to metabolic acidosis.
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Affiliation(s)
- Henrik Dimke
- Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark; Department of Nephrology, Odense University Hospital, Odense, Denmark.
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