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Broeker KAE, Schrankl J, Fuchs MAA, Kurtz A. Flexible and multifaceted: the plasticity of renin-expressing cells. Pflugers Arch 2022; 474:799-812. [PMID: 35511367 PMCID: PMC9338909 DOI: 10.1007/s00424-022-02694-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 04/21/2022] [Accepted: 04/22/2022] [Indexed: 12/14/2022]
Abstract
The protease renin, the key enzyme of the renin–angiotensin–aldosterone system, is mainly produced and secreted by juxtaglomerular cells in the kidney, which are located in the walls of the afferent arterioles at their entrance into the glomeruli. When the body’s demand for renin rises, the renin production capacity of the kidneys commonly increases by induction of renin expression in vascular smooth muscle cells and in extraglomerular mesangial cells. These cells undergo a reversible metaplastic cellular transformation in order to produce renin. Juxtaglomerular cells of the renin lineage have also been described to migrate into the glomerulus and differentiate into podocytes, epithelial cells or mesangial cells to restore damaged cells in states of glomerular disease. More recently, it could be shown that renin cells can also undergo an endocrine and metaplastic switch to erythropoietin-producing cells. This review aims to describe the high degree of plasticity of renin-producing cells of the kidneys and to analyze the underlying mechanisms.
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Affiliation(s)
- Katharina A E Broeker
- Institute of Physiology, University of Regensburg, Universitätsstraβe 31, D-93053 , Regensburg, Germany.
| | - Julia Schrankl
- Institute of Physiology, University of Regensburg, Universitätsstraβe 31, D-93053 , Regensburg, Germany
| | - Michaela A A Fuchs
- Institute of Physiology, University of Regensburg, Universitätsstraβe 31, D-93053 , Regensburg, Germany
| | - Armin Kurtz
- Institute of Physiology, University of Regensburg, Universitätsstraβe 31, D-93053 , Regensburg, Germany
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2
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Takiyama Y, Sera T, Nakamura M, Ishizeki K, Saijo Y, Yanagimachi T, Maeda M, Bessho R, Takiyama T, Kitsunai H, Sakagami H, Fujishiro D, Fujita Y, Makino Y, Abiko A, Hoshino M, Uesugi K, Yagi N, Ota T, Haneda M. Impacts of Diabetes and an SGLT2 Inhibitor on the Glomerular Number and Volume in db/db Mice, as Estimated by Synchrotron Radiation Micro-CT at SPring-8. EBioMedicine 2018; 36:329-346. [PMID: 30322799 PMCID: PMC6197731 DOI: 10.1016/j.ebiom.2018.09.048] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Revised: 09/26/2018] [Accepted: 09/26/2018] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND Recent large-scale clinical studies demonstrate that sodium-glucose cotransporter 2 (SGLT2) inhibitors protect the diabetic kidney. However, clinical and animal studies have not shown the changes of the total glomeruli in the whole kidney treated with SGLT2 inhibitors. METHODS We performed computed tomography (CT) imaging on mice using synchrotron radiation to investigate the impact of luseogliflozin, a SGLT2 inhibitor, on the number and volume of glomeruli in the whole kidney. FINDINGS We did not observe a significant difference in the total glomerular number (Nglom) among mice. Luseogliflozin redistributed the number of glomeruli in different regions, accompanied by the normalization of diabetes-augmented renal volume (Vkidney). Diabetic db/db mice had a larger glomerular volume in the mid-cortex than did control db/m mice, and luseogliflozin increased the glomerular volume in all renal cortical zones of the whole kidney in db/db mice. According to the multivariate regression analysis, hemoglobin A1c level was the most relevant determinant of Vkidney, not Nglom or mean glomerular volume (Vglom), indicating that hyperglycemia induced renal (tubular) hypertrophy, but not glomerular enlargement. Luseogliflozin increased hypoxia in the juxtamedullary region, sustained upregulated renal renin expression and plasma renin activity, and failed to decrease albuminuria by downregulating megalin in db/db mice. INTERPRETATION Based on our findings, SGLT2 inhibitors may alter glomerular distribution and size in addition to their glucose-lowering effects, presumably by affecting oxygen metabolism and humoral factors. FUND: Funding for this research was provided by The Japan Society for the Promotion of Science, the Japan Diabetes Foundation, and Asahikawa Medical University.
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Affiliation(s)
- Yumi Takiyama
- Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Japan.
| | - Toshihiro Sera
- Department of Mechanical Engineering, Faculty of Engineering, Kyushu University, Japan
| | - Masanori Nakamura
- Department of Electrical and Mechanical Engineering, Nagoya Institute of Technology, Japan
| | - Kanaki Ishizeki
- Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Japan
| | - Yasuaki Saijo
- Department of Health Science, Asahikawa Medical University, Japan
| | - Tsuyoshi Yanagimachi
- Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Japan
| | - Manami Maeda
- Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Japan
| | - Ryoichi Bessho
- Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Japan
| | - Takao Takiyama
- Department of Neurosurgery, Asahikawa Medical University, Japan
| | - Hiroya Kitsunai
- Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Japan
| | - Hidemitsu Sakagami
- Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Japan
| | - Daisuke Fujishiro
- Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Japan
| | - Yukihiro Fujita
- Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Japan
| | - Yuichi Makino
- Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Japan
| | - Atsuko Abiko
- Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Japan
| | - Masato Hoshino
- Research & Utilization Division, Japan Synchrotron Radiation Research Institute, Japan
| | - Kentaro Uesugi
- Research & Utilization Division, Japan Synchrotron Radiation Research Institute, Japan
| | - Naoto Yagi
- Research & Utilization Division, Japan Synchrotron Radiation Research Institute, Japan
| | - Tsuguhito Ota
- Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Japan
| | - Masakazu Haneda
- Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Japan
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Steppan D, Geis L, Pan L, Gross K, Wagner C, Kurtz A. Lack of connexin 40 decreases the calcium sensitivity of renin-secreting juxtaglomerular cells. Pflugers Arch 2018; 470:969-978. [PMID: 29427253 PMCID: PMC10751884 DOI: 10.1007/s00424-018-2119-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 01/24/2018] [Accepted: 02/02/2018] [Indexed: 11/29/2022]
Abstract
The so-called calcium paradoxon of renin describes the phenomenon that exocytosis of renin from juxtaglomerular cells of the kidney is stimulated by lowering of the extracellular calcium concentration. The yet poorly understood effect of extracellular calcium on renin secretion appears to depend on the function of the gap junction protein connexin 40 (Cx40) in renin-producing cells. This study aimed to elucidate the role of Cx40 for the calcium dependency of renin secretion in more detail by investigating if Cx40 function is really essential for the influence of extracellular calcium on renin secretion, if and how Cx40 affects intracellular calcium dynamics in renin-secreting cells and if Cx40-mediated gap junctional coupling of renin-secreting cells with the mesangial cell area is relevant for the influence of extracellular calcium on renin secretion. Renin secretion was studied in isolated perfused mouse kidneys. Calcium measurements were performed in renin-producing cells of microdissected glomeruli. The ultrastructure of renin-secreting cells was examined by electron microscopy. We found that Cx40 was not essential for stimulation of renin secretion by lowering of the extracellular calcium concentration. Instead, Cx40 increased the sensitivity of renin secretion response towards lowering of the extracellular calcium concentration. In line, the sensitivity and dynamics of intracellular calcium in response to lowering of extracellular calcium were dampened when renin-secreting cells lacked Cx40. Disruption of gap junctional coupling of renin-secreting cells by selective deletion of Cx40 from mesangial cells, however, did not change the stimulation of renin secretion by lowering of the extracellular calcium concentration. Deletion of Cx40 from renin cells but not from mesangial cells was associated with a shift of renin expression from perivascular cells of afferent arterioles to extraglomerular mesangial cells. Our findings suggest that Cx40 is not directly involved in the regulation of renin secretion by extracellular calcium. Instead, it appears that in renin-secreting cells of the kidney lacking Cx40, intracellular calcium dynamics and therefore also renin secretion are desensitized towards changes of extracellular calcium. Whether the dampened calcium response of renin-secreting cells lacking Cx40 function results from a direct involvement of Cx40 in intracellular calcium regulation or from the cell type shift of renin expression from perivascular to mesangial cells remains to be clarified. In any case, Cx40-mediated gap junctional coupling between renin and mesangial cells is not relevant for the calcium paradoxon of renin secretion.
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Affiliation(s)
- Dominik Steppan
- Institute of Physiology, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany.
| | - Lisa Geis
- Clinic for Nephrology, University Hospital Regensburg, Franz-Josef-Strauß-Allee 11, 93053, Regensburg, Germany
| | - Lin Pan
- Department of Pathology, Brigham and Women's Hospital, 652 NRB, 77 Ave Louis Pasteur, Boston, MA, 02115, USA
| | - Kenneth Gross
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Elm and Carlton Sts, Buffalo, NY, 14263-0001, USA
| | - Charlotte Wagner
- Institute of Physiology, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Armin Kurtz
- Institute of Physiology, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
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4
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Steppan D, Pan L, Gross KW, Kurtz A. Analysis of the calcium paradox of renin secretion. Am J Physiol Renal Physiol 2017; 315:F834-F843. [PMID: 29357428 DOI: 10.1152/ajprenal.00554.2017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The secretion of the protease renin from renal juxtaglomerular cells is enhanced by subnormal extracellular calcium concentrations. The mechanisms underlying this atypical effect of calcium have not yet been unraveled. We therefore aimed to characterize the effect of extracellular calcium concentration on calcium handling of juxtaglomerular cells and on renin secretion in more detail. For this purpose, we used a combination of experiments with isolated perfused mouse kidneys and direct calcium measurements in renin-secreting cells in situ. We found that lowering of the extracellular calcium concentration led to a sustained elevation of renin secretion. Electron-microscopical analysis of renin-secreting cells exposed to subnormal extracellular calcium concentrations revealed big omega-shaped structures resulting from the intracellular fusion and subsequent emptying of renin storage vesicles. The calcium concentration dependencies as well as the kinetics of changes were rather similar for renin secretion and for renovascular resistance. Since vascular resistance is fundamentally influenced by myosin light chain kinase (MLCK), myosin light chain phosphatase (MLCP), and Rho-associated protein kinase (Rho-K) activities, we examined the effects of MLCK-, MLCP-, and Rho-K inhibitors on renin secretion. Only MLCK inhibition stimulated renin secretion. Conversely, inhibition of MCLP activity lowered perfusate flow and strongly inhibited renin secretion, which could not be reversed by lowering of the extracellular calcium concentration. Renin-secreting cells and smooth muscle cells of afferent arterioles showed immunoreactivity of MLCK. These findings suggest that the inhibitory effect of calcium on renin secretion could be explained by phosphorylation-dependent processes under control of the MLCK.
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Affiliation(s)
- D Steppan
- Institute of Physiology, University of Regensburg , Regensburg , Germany
| | - L Pan
- Department of Pathology, Brigham and Women's Hospital , Boston, Massachusetts
| | - K W Gross
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute , Buffalo, New York
| | - A Kurtz
- Institute of Physiology, University of Regensburg , Regensburg , Germany
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5
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Buckley C, Nelson RJ, Mullins LJ, Sharp MGF, Fleming S, Kenyon CJ, Semprini S, Steppan D, Peti-Peterdi J, Kurtz A, Christian H, Mullins JJ. Phenotypic dissection of the mouse Ren1d knockout by complementation with human renin. J Biol Chem 2017; 293:1151-1162. [PMID: 29123029 PMCID: PMC5787795 DOI: 10.1074/jbc.ra117.000160] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 11/03/2017] [Indexed: 11/08/2022] Open
Abstract
Normal renin synthesis and secretion is important for the maintenance of juxtaglomerular apparatus architecture. Mice lacking a functional Ren1d gene are devoid of renal juxtaglomerular cell granules and exhibit an altered macula densa morphology. Due to the species-specificity of renin activity, transgenic mice are ideal models for experimentally investigating and manipulating expression patterns of the human renin gene in a native cellular environment without confounding renin–angiotensin system interactions. A 55-kb transgene encompassing the human renin locus was crossed onto the mouse Ren1d-null background, restoring granulation in juxtaglomerular cells. Correct processing of human renin in dense core granules was confirmed by immunogold labeling. After stimulation of the renin–angiotensin system, juxtaglomerular cells contained rhomboid protogranules with paracrystalline contents, dilated rough endoplasmic reticulum, and electron-lucent granular structures. However, complementation of Ren1d−/− mice with human renin was unable to rescue the abnormality seen in macula densa structure. The juxtaglomerular apparatus was still able to respond to tubuloglomerular feedback in isolated perfused juxtaglomerular apparatus preparations, although minor differences in glomerular tuft contractility and macula densa cell calcium handling were observed. This study reveals that the human renin protein is able to complement the mouse Ren1d−/− non-granulated defect and suggests that granulopoiesis requires a structural motif that is conserved between the mouse Ren1d and human renin proteins. It also suggests that the altered macula densa phenotype is related to the activity of the renin-1d enzyme in a local juxtaglomerular renin–angiotensin system.
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Affiliation(s)
- Charlotte Buckley
- From the University/BHF Centre for Cardiovascular Science, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom,
| | - Robert J Nelson
- From the University/BHF Centre for Cardiovascular Science, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
| | - Linda J Mullins
- From the University/BHF Centre for Cardiovascular Science, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
| | - Matthew G F Sharp
- From the University/BHF Centre for Cardiovascular Science, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
| | - Stewart Fleming
- the University of Dundee, Ninewells Hospital Medical School, Dundee DD1 9SY, Scotland
| | - Christopher J Kenyon
- From the University/BHF Centre for Cardiovascular Science, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
| | - Sabrina Semprini
- From the University/BHF Centre for Cardiovascular Science, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
| | - Dominik Steppan
- the Physiologisches Institut der Universität Regensburg, Regensburg D-93053, Germany
| | - Janos Peti-Peterdi
- the Department of Physiology and Biophysics and Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90089, and
| | - Armin Kurtz
- the Physiologisches Institut der Universität Regensburg, Regensburg D-93053, Germany
| | - Helen Christian
- the Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3QX, United Kingdom
| | - John J Mullins
- From the University/BHF Centre for Cardiovascular Science, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom,
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6
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Rider SA, Christian HC, Mullins LJ, Howarth AR, MacRae CA, Mullins JJ. Zebrafish mesonephric renin cells are functionally conserved and comprise two distinct morphological populations. Am J Physiol Renal Physiol 2017; 312:F778-F790. [PMID: 28179256 DOI: 10.1152/ajprenal.00608.2016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 01/17/2017] [Accepted: 02/01/2017] [Indexed: 12/20/2022] Open
Abstract
Zebrafish provide an excellent model in which to assess the role of the renin-angiotensin system in renal development, injury, and repair. In contrast to mammals, zebrafish kidney organogenesis terminates with the mesonephros. Despite this, the basic functional structure of the nephron is conserved across vertebrates. The relevance of teleosts for studies relating to the regulation of the renin-angiotensin system was established by assessing the phenotype and functional regulation of renin-expressing cells in zebrafish. Transgenic fluorescent reporters for renin (ren), smooth muscle actin (acta2), and platelet-derived growth factor receptor-beta (pdgfrb) were studied to determine the phenotype and secretory ultrastructure of perivascular renin-expressing cells. Whole kidney ren transcription responded to altered salinity, pharmacological renin-angiotensin system inhibition, and renal injury. Mesonephric ren-expressing cells occupied niches at the preglomerular arteries and afferent arterioles, forming intermittent epithelioid-like multicellular clusters exhibiting a granular secretory ultrastructure. In contrast, renin cells of the efferent arterioles were thin bodied and lacked secretory granules. Renin cells expressed the perivascular cell markers acta2 and pdgfrb Transcriptional responses of ren to physiological challenge support the presence of a functional renin-angiotensin system and are consistent with the production of active renin. The reparative capability of the zebrafish kidney was harnessed to demonstrate that ren transcription is a marker for renal injury and repair. Our studies demonstrate substantive conservation of renin regulation across vertebrates, and ultrastructural studies of renin cells reveal at least two distinct morphologies of mesonephric perivascular ren-expressing cells.
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Affiliation(s)
- Sebastien A Rider
- University/British Heart Foundation Centre for Cardiovascular Science, The Queen's Medical Research Institute, Little France, The University of Edinburgh, Edinburgh, United Kingdom;
| | - Helen C Christian
- Department of Physiology, Anatomy and Genetics, Oxford, United Kingdom; and
| | - Linda J Mullins
- University/British Heart Foundation Centre for Cardiovascular Science, The Queen's Medical Research Institute, Little France, The University of Edinburgh, Edinburgh, United Kingdom
| | - Amelia R Howarth
- University/British Heart Foundation Centre for Cardiovascular Science, The Queen's Medical Research Institute, Little France, The University of Edinburgh, Edinburgh, United Kingdom
| | - Calum A MacRae
- Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - John J Mullins
- University/British Heart Foundation Centre for Cardiovascular Science, The Queen's Medical Research Institute, Little France, The University of Edinburgh, Edinburgh, United Kingdom
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7
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Buckley C, Dun AR, Peter A, Bellamy C, Gross KW, Duncan RR, Mullins JJ. Bimodal dynamics of granular organelles in primary renin-expressing cells revealed using TIRF microscopy. Am J Physiol Renal Physiol 2016; 312:F200-F209. [PMID: 28069661 DOI: 10.1152/ajprenal.00384.2016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 10/12/2016] [Accepted: 11/04/2016] [Indexed: 12/31/2022] Open
Abstract
Renin is the initiator and rate-limiting factor in the renin-angiotensin blood pressure regulation system. Although renin is not exclusively produced in the kidney, in nonmurine species the synthesis and secretion of the active circulatory enzyme is confined almost exclusively to the dense core granules of juxtaglomerular (JG) cells, where prorenin is processed and stored for release via a regulated pathway. Despite its importance, the structural organization and regulation of granules within these cells is not well understood, in part due to the difficulty in culturing primary JG cells in vitro and the lack of appropriate cell lines. We have streamlined the isolation and culture of primary renin-expressing cells suitable for high-speed, high-resolution live imaging using a Percoll gradient-based procedure to purify cells from RenGFP+ transgenic mice. Fibronectin-coated glass coverslips proved optimal for the adhesion of renin-expressing cells and facilitated live cell imaging at the plasma membrane of primary renin cells using total internal reflection fluorescence microscopy (TIRFM). To obtain quantitative data on intracellular function, we stained mixed granule and lysosome populations with Lysotracker Red and stimulated cells using 100 nM isoproterenol. Analysis of membrane-proximal acidic granular organelle dynamics and behavior within renin-expressing cells revealed the existence of two populations of granular organelles with distinct functional responses following isoproterenol stimulation. The application of high-resolution techniques for imaging JG and other specialized kidney cells provides new opportunities for investigating renal cell biology.
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Affiliation(s)
- Charlotte Buckley
- BHF/University Centre for Cardiovascular Science, University of Edinburgh, Queen's Medical Research Institute, Edinburgh, United Kingdom;
| | - Alison R Dun
- Edinburgh Super Resolution Imaging Consortium, Heriot-Watt University, Riccarton Campus, Edinburgh, United Kingdom
| | - Audrey Peter
- BHF/University Centre for Cardiovascular Science, University of Edinburgh, Queen's Medical Research Institute, Edinburgh, United Kingdom
| | - Christopher Bellamy
- Department of Pathology, Royal Infirmary of Edinburgh, Edinburgh, United Kingdom; and
| | - Kenneth W Gross
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York
| | - Rory R Duncan
- Edinburgh Super Resolution Imaging Consortium, Heriot-Watt University, Riccarton Campus, Edinburgh, United Kingdom
| | - John J Mullins
- BHF/University Centre for Cardiovascular Science, University of Edinburgh, Queen's Medical Research Institute, Edinburgh, United Kingdom
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8
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Abstract
The kidneys are important endocrine organs. They secrete humoral factors, such as calcitriol, erythropoietin, klotho, and renin into the circulation, and therefore, they are essentially involved in the regulation of a variety of processes ranging from bone formation to erythropoiesis. The endocrine functions are established by cells, such as proximal or distal tubular cells, renocortical interstitial cells, or mural cells of afferent arterioles. These endocrine cells are either fixed in number, such as tubular cells, which individually and gradually upregulate or downregulate hormone production, or they belong to a pool of cells, which display a recruitment behavior, such as erythropoietin- and renin-producing cells. In the latter case, regulation of humoral function occurs via (de)recruitment of active endocrine cells. As a consequence renin- and erythropoietin-producing cells in the kidney show a high degree of plasticity by reversibly switching between distinct cell states. In this review, we will focus on the characteristics of renin- and of erythropoietin-producing cells, especially on their origin and localization, their reversible transformations, and the mediators, which are responsible for transformation. Finally, we will discuss a possible interconversion of renin and erythropoietin expression.
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Affiliation(s)
- Birgül Kurt
- Institute of Physiology, University of Regensburg, Regensburg, Germany
| | - Armin Kurtz
- Institute of Physiology, University of Regensburg, Regensburg, Germany
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9
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Tinning AR, Jensen BL, Schweda F, Machura K, Hansen PBL, Stubbe J, Gramsbergen JB, Madsen K. The water channel aquaporin-1 contributes to renin cell recruitment during chronic stimulation of renin production. Am J Physiol Renal Physiol 2014; 307:F1215-26. [DOI: 10.1152/ajprenal.00136.2014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Both the processing and release of secretory granules involve water movement across granule membranes. It was hypothesized that the water channel aquaporin (AQP)1 directly contributes to the recruitment of renin-positive cells in the afferent arteriole. AQP1−/− and AQP1+/+ mice were fed a low-salt (LS) diet [0.004% (wt/wt) NaCl] for 7 days and given enalapril [angiotensin-converting enzyme inhibitor (ACEI), 0.1 mg/ml] in drinking water for 3 days. There were no differences in plasma renin concentration at baseline. After LS-ACEI, plasma renin concentrations increased markedly in both genotypes but was significantly lower in AQP1−/− mice compared with AQP1+/+ mice. Tissue renin concentrations were higher in AQP1−/− mice, and renin mRNA levels were not different between genotypes. Mean arterial blood pressure was not different at baseline and during LS diet but decreased significantly in both genotypes after the addition of ACEI; the response was faster in AQP1−/− mice but then stabilized at a similar level. Renin release after 200 μl blood withdrawal was not different. Isoprenaline-stimulated renin release from isolated perfused kidneys did not differ between genotypes. Cortical tissue norepinephrine concentrations were lower after LS-ACEI compared with baseline with no difference between genotypes. Plasma nitrite/nitrate concentrations were unaffected by genotype and LS-ACEI. In AQP1−/− mice, the number of afferent arterioles with recruitment was significantly lower compared with AQP1+/+ mice after LS-ACEI. We conclude that AQP1 is not necessary for acutely stimulated renin secretion in vivo and from isolated perfused kidneys, whereas recruitment of renin-positive cells in response to chronic stimulation is attenuated or delayed in AQP1−/− mice.
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Affiliation(s)
- Anne R. Tinning
- Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Boye L. Jensen
- Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Frank Schweda
- Institute of Physiology, University of Regensburg, Regensburg, Germany
| | - Katharina Machura
- Institute of Physiology, University of Regensburg, Regensburg, Germany
| | - Pernille B. L. Hansen
- Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Jane Stubbe
- Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Jan Bert Gramsbergen
- Department of Neurobiology Research, University of Southern Denmark, Odense, Denmark; and
| | - Kirsten Madsen
- Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
- Department of Pathology, Odense University Hospital, Odense, Denmark
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10
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Xa LK, Lacombe MJ, Mercure C, Lazure C, Reudelhuber TL. General lysosomal hydrolysis can process prorenin accurately. Am J Physiol Regul Integr Comp Physiol 2014; 307:R505-13. [PMID: 24965790 DOI: 10.1152/ajpregu.00467.2013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Renin, an aspartyl protease that catalyzes the rate-limiting step of the renin-angiotensin system, is first synthesized as an inactive precursor, prorenin. Prorenin is activated by the proteolytic removal of an amino terminal prosegment in the dense granules of the juxtaglomerular (JG) cells of the kidney by one or more proteases whose identity is uncertain but commonly referred to as the prorenin-processing enzyme (PPE). Because several extrarenal tissues secrete only prorenin, we tested the hypothesis that the unique ability of JG cells to produce active renin might be explained by the existence of a PPE whose expression is restricted to JG cells. We found that inducing renin production by the mouse kidney by up to 20-fold was not associated with the concomitant induction of candidate PPEs. Because the renin-containing granules of JG cells also contain several lysosomal hydrolases, we engineered mouse Ren1 prorenin to be targeted to the classical vesicular lysosomes of cultured HEK-293 cells, where it was accurately processed and stored. Furthermore, we found that HEK cell lysosomes hydrolyzed any artificial extensions placed on the protein and that active renin was extraordinarily resistant to proteolytic degradation. Altogether, our results demonstrate that accurate processing of prorenin is not restricted to JG cells but can occur in classical vesicular lysosomes of heterologous cells. The implication is that renin production may not require a specific PPE but rather can be achieved by general hydrolysis in the lysosome-like granules of JG cells.
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Affiliation(s)
- Lucie K Xa
- Laboratories of Molecular Biochemistry of Hypertension and Division of Experimental Medicine, Faculty of Medicine, McGill University, Montreal, Quebec, Canada; and
| | | | | | - Claude Lazure
- Neuropeptide Structure and Metabolism, Institut de Recherches Cliniques de Montréal, Montreal, Quebec, Canada; Division of Experimental Medicine, Faculty of Medicine, McGill University, Montreal, Quebec, Canada; and Department of Medicine, Université de Montréal, Montreal, Quebec, Canada
| | - Timothy L Reudelhuber
- Laboratories of Molecular Biochemistry of Hypertension and Division of Experimental Medicine, Faculty of Medicine, McGill University, Montreal, Quebec, Canada; and Department of Medicine, Université de Montréal, Montreal, Quebec, Canada
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Kurt B, Karger C, Wagner C, Kurtz A. Control of renin secretion from kidneys with renin cell hyperplasia. Am J Physiol Renal Physiol 2014; 306:F327-32. [PMID: 24285498 DOI: 10.1152/ajprenal.00536.2013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In states of loss-of-function mutations of the renin-angiotensin-aldosterone system, kidneys develop a strong hyperplasia of renin-producing cells. Those additional renin cells are located outside the classic juxtaglomerular areas, mainly in the walls of preglomerular vessels and most prominently in multilayers surrounding afferent arterioles. Since the functional behavior of those ectopic renin cells is yet unknown, we aimed to characterize the control of renin secretion from kidneys with renin cell hyperplasia. As a model, we used kidneys from mice lacking aldosterone synthase (AS⁻/⁻ mice), which displayed 10-fold elevations of renin mRNA and plasma renin concentrations. On the absolute level, renin secretion from isolated AS⁻/⁻ kidneys was more than 10-fold increased over wild-type kidneys. On the relative level, the stimulation of renin secretion by the β-adrenergic activator isoproterenol or by lowering of the concentration of extracellular Ca²⁺ was very similar between the two genotypes. In addition, the inhibitory effects of ANG II and of perfusion pressure were similar between the two genotypes. Deletion of connexin40 blunted the pressure dependency of renin secretion and the stimulatory effect of low extracellular Ca²⁺ on renin secretion in the same manner in kidneys of AS⁻/⁻ mice as in wild-type mice. Our findings suggest a high degree of functional similarity between renin cells originating during development and located at different positions in the adult kidney. They also suggest a high similarity in the expression of membrane proteins relevant for the control of renin secretion, such as β₁-adrenergic receptors, ANG II type 1 receptors, and connexin40.
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Affiliation(s)
- Birgül Kurt
- Physiologisches Institut, Universität Regensburg, Universitätsstrasse 31, Regensburg D-93053, Germany.
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