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Gyarmati G, Shroff UN, Riquier-Brison A, Kriz W, Kaissling B, Neal CR, Arkill KP, Ahmadi N, Gill IS, Moon JY, Desposito D, Peti-Peterdi J. A new view of macula densa cell microanatomy. Am J Physiol Renal Physiol 2021; 320:F492-F504. [PMID: 33491562 DOI: 10.1152/ajprenal.00546.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Although macula densa (MD) cells are chief regulatory cells in the nephron with unique microanatomical features, they have been difficult to study in full detail due to their inaccessibility and limitations in earlier microscopy techniques. The present study used a new mouse model with a comprehensive imaging approach to visualize so far unexplored microanatomical features of MD cells, their regulation, and functional relevance. MD-GFP mice with conditional and partial induction of green fluorescent protein (GFP) expression, which specifically and intensely illuminated only single MD cells, were used with fluorescence microscopy of fixed tissue and live MD cells in vitro and in vivo with complementary electron microscopy of the rat, rabbit, and human kidney. An elaborate network of major and minor cell processes, here named maculapodia, were found at the cell base, projecting toward other MD cells and the glomerular vascular pole. The extent of maculapodia showed upregulation by low dietary salt intake and the female sex. Time-lapse imaging of maculapodia revealed highly dynamic features including rapid outgrowth and an extensive vesicular transport system. Electron microscopy of rat, rabbit, and human kidneys and three-dimensional volume reconstruction in optically cleared whole-mount MD-GFP mouse kidneys further confirmed the presence and projections of maculapodia into the extraglomerular mesangium and afferent and efferent arterioles. The newly identified dynamic and secretory features of MD cells suggest the presence of novel functional and molecular pathways of cell-to-cell communication in the juxtaglomerular apparatus between MD cells and between MD and other target cells.NEW & NOTEWORTHY This study illuminated a physiologically regulated dense network of basal cell major and minor processes (maculapodia) in macula densa (MD) cells. The newly identified dynamic and secretory features of these microanatomical structures suggest the presence of novel functional and molecular pathways of cell-to-cell communication in the juxtaglomerular apparatus between MD and other target cells. Detailed characterization of the function and molecular details of MD cell intercellular communications and their role in physiology and disease warrant further studies.
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Affiliation(s)
- Georgina Gyarmati
- Departments of Physiology and Neuroscience, and Medicine, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California
| | - Urvi Nikhil Shroff
- Departments of Physiology and Neuroscience, and Medicine, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California
| | - Anne Riquier-Brison
- Departments of Physiology and Neuroscience, and Medicine, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California
| | - Wilhelm Kriz
- Centre for Biomedicine and Medical Technology Mannheim, Neuroanatomy, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | | | - Christopher R Neal
- Bristol Renal, Bristol Heart Institute, Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Kenton P Arkill
- Division of Cancer and Stem Cells, School of Medicine, University of Nottingham Biodiscovery Institute, University Park, United Kingdom
| | - Nariman Ahmadi
- Institute of Urology, Catherine & Joseph Aresty Department of Urology, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Inderbir S Gill
- Institute of Urology, Catherine & Joseph Aresty Department of Urology, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Ju-Young Moon
- Departments of Physiology and Neuroscience, and Medicine, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California
| | - Dorinne Desposito
- Departments of Physiology and Neuroscience, and Medicine, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California
| | - János Peti-Peterdi
- Departments of Physiology and Neuroscience, and Medicine, Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, California
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Abstract
Autocrine and paracrine signaling in the kidney adds an extra level of diversity and complexity to renal physiology. The extensive scientific production on the topic precludes easy understanding of the fundamental purpose of the vast number of molecules and systems that influence the renal function. This systematic review provides the broader pen strokes for a collected image of renal paracrine signaling. First, we recapitulate the essence of each paracrine system one by one. Thereafter the single components are merged into an overarching physiological concept. The presented survey shows that despite the diversity in the web of paracrine factors, the collected effect on renal function may not be complicated after all. In essence, paracrine activation provides an intelligent system that perceives minor perturbations and reacts with a coordinated and integrated tissue response that relieves the work load from the renal epithelia and favors diuresis and natriuresis. We suggest that the overall function of paracrine signaling is reno-protection and argue that renal paracrine signaling and self-regulation are two sides of the same coin. Thus local paracrine signaling is an intrinsic function of the kidney, and the overall renal effect of changes in blood pressure, volume load, and systemic hormones will always be tinted by its paracrine status.
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Affiliation(s)
- Jens Leipziger
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; and Aarhus Institute of Advanced Studies (AIAS), Aarhus University, Aarhus, Denmark
| | - Helle Praetorius
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; and Aarhus Institute of Advanced Studies (AIAS), Aarhus University, Aarhus, Denmark
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Abstract
PURPOSE OF REVIEW In this review, we summarized the current knowledge of connecting tubule-glomerular feedback (CTGF), a novel mechanism of renal microcirculation regulation that integrates sodium handling in the connecting tubule (CNT) with kidney hemodynamics. RECENT FINDINGS Connecting tubule-glomerular feedback is a crosstalk communication between the CNT and the afferent arteriole (Af-Art), initiated by sodium chloride through the epithelial sodium channel (ENaC). High sodium in the CNT induces Af-Art vasodilation, increasing glomerular pressure and the glomerular filtration rate and favoring sodium excretion. CTGF antagonized and reset tubuloglomerular feedback and thus increased sodium excretion. CTGF is absent in spontaneous hypertensive rats and is overactivated in Dahl salt-sensitive rats. CTGF is also modulated by angiotensin II and aldosterone. CTGF is a feedback mechanism that integrates sodium handling in the CNT with glomerular hemodynamics. Lack of CTGF could promote hypertension, and CTGF overactivation may favor glomerular damage and proteinuria. More studies are needed to explore the alterations in renal microcirculation and the role of these alterations in the genesis of hypertension and glomerular damage in animals and humans. KEY POINTS • CTGF is a vasodilator mechanism that regulates afferent arteriole resistance. • CTGF is absent in spontaneous hypertensive rats and overactivated in Dahl salt-sensitive rats. • CTGF in excess may promote glomerular damage and proteinuria, while the absence may participate in sodium retention and hypertension.
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Affiliation(s)
- Cesar A Romero
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, 2799 West Grand Boulevard, Detroit, MI, 48202-2689, USA.
| | - Oscar A Carretero
- Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, 2799 West Grand Boulevard, Detroit, MI, 48202-2689, USA
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Song J, Wang L, Fan F, Wei J, Zhang J, Lu Y, Fu Y, Wang S, Juncos LA, Liu R. Role of the Primary Cilia on the Macula Densa and Thick Ascending Limbs in Regulation of Sodium Excretion and Hemodynamics. Hypertension 2017; 70:324-333. [PMID: 28607127 PMCID: PMC5507816 DOI: 10.1161/hypertensionaha.117.09584] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Revised: 05/15/2017] [Accepted: 05/21/2017] [Indexed: 01/28/2023]
Abstract
We investigated the significance of the primary cilia on the macula densa and thick ascending limb (TAL) in regulation of renal hemodynamics, sodium excretion, and blood pressure in this study. A tissue-specific primary cilia knock-out (KO) mouse line was generated by crossing NKCC2-Cre mice with IFT88-Δ/flox mice (NKCC2CRE; IFT88Δ/flox), in which the primary cilia were deleted from the macula densa and TAL. NO generation was measured with a fluorescent dye (4,5-diaminofluorescein diacetate) in isolated perfused juxtaglomerular apparatus. Deletion of the cilia reduced NO production by 56% and 42% in the macula densa and TAL, respectively. NO generation by the macula densa was inhibited by both a nonselective and a selective nitric oxide synthesis inhibitors, whereas TAL-produced NO was inhibited by a nonselective and not by a selective NO synthesis 1 inhibitor. The tubuloglomerular feedback response was enhanced in the KO mice both in vitro measured with isolated perfused juxtaglomerular apparatuses and in vivo measured with micropuncture. In response to an acute volume expansion, the KO mice exhibited limited glomerular filtration rate elevation and impaired sodium excretion compared with the wild-type mice. The mean arterial pressure measured with telemetry was the same for wild-type and KO mice fed a normal salt diet. After a high salt diet, the mean arterial pressure increased by 17.4±1.6 mm Hg in the KO mice. On the basis of these findings, we concluded that the primary cilia on the macula densa and TAL play an essential role in the control of sodium excretion and blood pressure.
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Affiliation(s)
- Jiangping Song
- From the Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (J.S., L.W., J.W., J.Z., S.W., R.L.); State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China (J.S.); and Department of Pharmacology and Medicine, University of Mississippi Medical Center, Jackson (F.F., Y.L., Y.F., L.A.J.)
| | - Lei Wang
- From the Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (J.S., L.W., J.W., J.Z., S.W., R.L.); State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China (J.S.); and Department of Pharmacology and Medicine, University of Mississippi Medical Center, Jackson (F.F., Y.L., Y.F., L.A.J.)
| | - Fan Fan
- From the Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (J.S., L.W., J.W., J.Z., S.W., R.L.); State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China (J.S.); and Department of Pharmacology and Medicine, University of Mississippi Medical Center, Jackson (F.F., Y.L., Y.F., L.A.J.)
| | - Jin Wei
- From the Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (J.S., L.W., J.W., J.Z., S.W., R.L.); State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China (J.S.); and Department of Pharmacology and Medicine, University of Mississippi Medical Center, Jackson (F.F., Y.L., Y.F., L.A.J.)
| | - Jie Zhang
- From the Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (J.S., L.W., J.W., J.Z., S.W., R.L.); State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China (J.S.); and Department of Pharmacology and Medicine, University of Mississippi Medical Center, Jackson (F.F., Y.L., Y.F., L.A.J.)
| | - Yan Lu
- From the Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (J.S., L.W., J.W., J.Z., S.W., R.L.); State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China (J.S.); and Department of Pharmacology and Medicine, University of Mississippi Medical Center, Jackson (F.F., Y.L., Y.F., L.A.J.)
| | - Yiling Fu
- From the Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (J.S., L.W., J.W., J.Z., S.W., R.L.); State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China (J.S.); and Department of Pharmacology and Medicine, University of Mississippi Medical Center, Jackson (F.F., Y.L., Y.F., L.A.J.)
| | - Shaohui Wang
- From the Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (J.S., L.W., J.W., J.Z., S.W., R.L.); State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China (J.S.); and Department of Pharmacology and Medicine, University of Mississippi Medical Center, Jackson (F.F., Y.L., Y.F., L.A.J.)
| | - Luis A Juncos
- From the Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (J.S., L.W., J.W., J.Z., S.W., R.L.); State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China (J.S.); and Department of Pharmacology and Medicine, University of Mississippi Medical Center, Jackson (F.F., Y.L., Y.F., L.A.J.)
| | - Ruisheng Liu
- From the Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (J.S., L.W., J.W., J.Z., S.W., R.L.); State Key Laboratory of Cardiovascular Disease, National Center for Cardiovascular Diseases, Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China (J.S.); and Department of Pharmacology and Medicine, University of Mississippi Medical Center, Jackson (F.F., Y.L., Y.F., L.A.J.).
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Wang L, Shen C, Liu H, Wang S, Chen X, Roman RJ, Juncos LA, Lu Y, Wei J, Zhang J, Yip KP, Liu R. Shear stress blunts tubuloglomerular feedback partially mediated by primary cilia and nitric oxide at the macula densa. Am J Physiol Regul Integr Comp Physiol 2015; 309:R757-66. [PMID: 26269519 PMCID: PMC4666931 DOI: 10.1152/ajpregu.00173.2015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 08/05/2015] [Indexed: 02/04/2023]
Abstract
The present study tested whether primary cilia on macula densa serve as a flow sensor to enhance nitric oxide synthase 1 (NOS1) activity and inhibit tubuloglomerular feedback (TGF). Isolated perfused macula densa was loaded with calcein red and 4,5-diaminofluorescein diacetate to monitor cell volume and nitric oxide (NO) generation. An increase in tubular flow rate from 0 to 40 nl/min enhanced NO production by 40.0 ± 1.2%. The flow-induced NO generation was blocked by an inhibitor of NOS1 but not by inhibition of the Na/K/2Cl cotransporter or the removal of electrolytes from the perfusate. NO generation increased from 174.8 ± 21 to 276.1 ± 24 units/min in cultured MMDD1 cells when shear stress was increased from 0.5 to 5.0 dynes/cm(2). The shear stress-induced NO generation was abolished in MMDD1 cells in which the cilia were disrupted using a siRNA to ift88. Increasing the NaCl concentration of the tubular perfusate from 10 to 80 mM NaCl in the isolated perfused juxtaglomerular preparation reduced the diameter of the afferent arteriole by 3.8 ± 0.1 μm. This response was significantly blunted to 2.5 ± 0.2 μm when dextran was added to the perfusate to increase the viscosity and shear stress. Inhibition of NOS1 blocked the effect of dextran on TGF response. In vitro, the effects of raising perfusate viscosity with dextran on tubular hydraulic pressure were minimized by reducing the outflow resistance to avoid stretching of tubular cells. These results suggest that shear stress stimulates primary cilia on the macula densa to enhance NO generation and inhibit TGF responsiveness.
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Affiliation(s)
- Lei Wang
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida
| | - Chunyu Shen
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida; Department of Forensic Pathology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; and
| | - Haifeng Liu
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida
| | - Shaohui Wang
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida
| | - Xinshan Chen
- Department of Forensic Pathology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; and
| | - Richard J Roman
- Department of Physiology/Pharmacology, University of Mississippi Medical Center, Jackson Mississippi
| | - Luis A Juncos
- Department of Physiology/Pharmacology, University of Mississippi Medical Center, Jackson Mississippi
| | - Yan Lu
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida; Department of Physiology/Pharmacology, University of Mississippi Medical Center, Jackson Mississippi
| | - Jin Wei
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida
| | - Jie Zhang
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida
| | - Kay-Pong Yip
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida
| | - Ruisheng Liu
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida;
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Abstract
Intrarenal autoregulatory mechanisms maintain renal blood flow (RBF) and glomerular filtration rate (GFR) independent of renal perfusion pressure (RPP) over a defined range (80-180 mmHg). Such autoregulation is mediated largely by the myogenic and the macula densa-tubuloglomerular feedback (MD-TGF) responses that regulate preglomerular vasomotor tone primarily of the afferent arteriole. Differences in response times allow separation of these mechanisms in the time and frequency domains. Mechanotransduction initiating the myogenic response requires a sensing mechanism activated by stretch of vascular smooth muscle cells (VSMCs) and coupled to intracellular signaling pathways eliciting plasma membrane depolarization and a rise in cytosolic free calcium concentration ([Ca(2+)]i). Proposed mechanosensors include epithelial sodium channels (ENaC), integrins, and/or transient receptor potential (TRP) channels. Increased [Ca(2+)]i occurs predominantly by Ca(2+) influx through L-type voltage-operated Ca(2+) channels (VOCC). Increased [Ca(2+)]i activates inositol trisphosphate receptors (IP3R) and ryanodine receptors (RyR) to mobilize Ca(2+) from sarcoplasmic reticular stores. Myogenic vasoconstriction is sustained by increased Ca(2+) sensitivity, mediated by protein kinase C and Rho/Rho-kinase that favors a positive balance between myosin light-chain kinase and phosphatase. Increased RPP activates MD-TGF by transducing a signal of epithelial MD salt reabsorption to adjust afferent arteriolar vasoconstriction. A combination of vascular and tubular mechanisms, novel to the kidney, provides for high autoregulatory efficiency that maintains RBF and GFR, stabilizes sodium excretion, and buffers transmission of RPP to sensitive glomerular capillaries, thereby protecting against hypertensive barotrauma. A unique aspect of the myogenic response in the renal vasculature is modulation of its strength and speed by the MD-TGF and by a connecting tubule glomerular feedback (CT-GF) mechanism. Reactive oxygen species and nitric oxide are modulators of myogenic and MD-TGF mechanisms. Attenuated renal autoregulation contributes to renal damage in many, but not all, models of renal, diabetic, and hypertensive diseases. This review provides a summary of our current knowledge regarding underlying mechanisms enabling renal autoregulation in health and disease and methods used for its study.
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Affiliation(s)
- Mattias Carlström
- Department of Medicine, Division of Nephrology and Hypertension and Hypertension, Kidney and Vascular Research Center, Georgetown University, Washington, District of Columbia; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden; and Department of Cell Biology and Physiology, UNC Kidney Center, and McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Christopher S Wilcox
- Department of Medicine, Division of Nephrology and Hypertension and Hypertension, Kidney and Vascular Research Center, Georgetown University, Washington, District of Columbia; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden; and Department of Cell Biology and Physiology, UNC Kidney Center, and McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - William J Arendshorst
- Department of Medicine, Division of Nephrology and Hypertension and Hypertension, Kidney and Vascular Research Center, Georgetown University, Washington, District of Columbia; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden; and Department of Cell Biology and Physiology, UNC Kidney Center, and McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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Liu ZZ, Schmerbach K, Lu Y, Perlewitz A, Nikitina T, Cantow K, Seeliger E, Persson PB, Patzak A, Liu R, Sendeski MM. Iodinated contrast media cause direct tubular cell damage, leading to oxidative stress, low nitric oxide, and impairment of tubuloglomerular feedback. Am J Physiol Renal Physiol 2014; 306:F864-72. [PMID: 24431205 DOI: 10.1152/ajprenal.00302.2013] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Iodinated contrast media (CM) have adverse effects that may result in contrast-induced acute kidney injury. Oxidative stress is believed to play a role in CM-induced kidney injury. We test the hypothesis that oxidative stress and reduced nitric oxide in tubules are consequences of CM-induced direct cell damage and that increased local oxidative stress may increase tubuloglomerular feedback. Rat thick ascending limbs (TAL) were isolated and perfused. Superoxide and nitric oxide were quantified using fluorescence techniques. Cell death rate was estimated using propidium iodide and trypan blue. The function of macula densa and tubuloglomerular feedback responsiveness were measured in isolated, perfused juxtaglomerular apparatuses (JGA) of rabbits. The expression of genes related to oxidative stress and the activity of superoxide dismutase (SOD) were investigated in the renal medulla of rats that received CM. CM increased superoxide concentration and reduced nitric oxide bioavailability in TAL. Propidium iodide fluorescence and trypan blue uptake increased more in CM-perfused TAL than in controls, indicating increased rate of cell death. There were no marked acute changes in the expression of genes related to oxidative stress in medullary segments of Henle's loop. SOD activity did not differ between CM and control groups. The tubuloglomerular feedback in isolated JGA was increased by CM. Tubular cell damage and accompanying oxidative stress in our model are consequences of CM-induced direct cell damage, which also modifies the tubulovascular interaction at the macula densa, and may therefore contribute to disturbances of renal perfusion and filtration.
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Affiliation(s)
- Zhi Zhao Liu
- Institut für Vegetative Physiologie, Charité, Universitätsmedizin Berlin, Berlin, Germany.
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Casellas D. Methods for imaging Renin-synthesizing, -storing, and -secreting cells. Int J Hypertens 2009; 2010:298747. [PMID: 20948562 PMCID: PMC2949082 DOI: 10.4061/2010/298747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Revised: 07/07/2009] [Accepted: 09/08/2009] [Indexed: 12/04/2022] Open
Abstract
Renin-producing cells have been the object of intense research efforts for the past fifty years within the field of hypertension. Two decades ago, research focused on the concept and characterization of the intrarenal renin-angiotensin system. Early morphological studies led to the concept of the juxtaglomerular apparatus, a minute organ that links tubulovascular structures and function at the single nephron level. The kidney, thus, appears as a highly "topological organ" in which anatomy and function are intimately linked. This point is reflected by a concurrent and constant development of functional and structural approaches. After summarizing our current knowledge about renin cells and their distribution along the renal vascular tree, particularly along glomerular afferent arterioles, we reviewed a variety of imaging techniques that permit a fine characterization of renin synthesis, storage, and release at the single-arteriolar, -cell, or -granule level. Powerful tools such as multiphoton microscopy and transgenesis bear the promises of future developments of the field.
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Affiliation(s)
- Daniel Casellas
- Groupe Rein et Hypertension (EA3127), Institut Universitaire de Recherche Clinique, 641 Avenue du Doyen Giraud, 34093 Montpellier Cédex 5, France
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Navar LG, Arendshorst WJ, Pallone TL, Inscho EW, Imig JD, Bell PD. The Renal Microcirculation. Microcirculation 2008. [DOI: 10.1016/b978-0-12-374530-9.00015-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
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Liu R, Persson AEG. Simultaneous changes of cell volume and cytosolic calcium concentration in macula densa cells caused by alterations of luminal NaCl concentration. J Physiol 2005; 563:895-901. [PMID: 15661823 PMCID: PMC1665624 DOI: 10.1113/jphysiol.2004.078154] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Cell volume and cytosolic Ca(2+) concentration ([Ca(2+)](i)) were measured in rabbit macula densa (MD) cells loaded with calcein and Fura Red using confocal microscopy. [Ca(2+)](i) was also analysed with Indo-1 and fura-2. We used isolated microperfused thick ascending limbs with attached glomerulus. The results showed that when the luminal NaCl concentration ('NaCl') was decreased from 35 to 10 mM, the cell volume decreased by 10.4%, and [Ca(2+)](i) increased by 9.5%. This increase was inhibited in Ca(2+)-free solution. When luminal [NaCl] was changed from 35 to 135 mM, the cell volume increased by 15.1%, and [Ca(2+)](i) did not change. The cell volume alterations were not different in Ca(2+)-free solutions. Using Indo-1, basal [Ca(2+)](i) in MD cells was 107.8 nM. When luminal [NaCl] was changed from 135 to 10 mm, [Ca(2)](i) increased by 23.5 nM. Using fura-2, the basal [Ca(2+)](i) in MD cells was 115.3 nM, and when luminal [NaCl] was changed from 135 or 35 to 10 mM, [Ca(2+)](i) change was 30.1 or 10.6 nM, respectively. An increase in [NaCl] caused no change in [Ca(2+)](i). In Ca(2+)-free solution, no change in [Ca(2+)](i) occurred. A stepwise decrease in luminal [NaCl] resulted in a sigmoid increase in [Ca(2+)](i) in MD cells. The steepest part of the curve was between 70 and 10 mM. In conclusion, we found that MD cells have cell volume regulation, and that [Ca(2+)](i) elevation caused by decreased luminal [NaCl] is independent of the cell volume.
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Affiliation(s)
- Ruisheng Liu
- Department of Medical Cell Biology, Uppsala University, BMC Box 571, S-75123 Uppsala, Sweden
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Abstract
Macula densa cells are renal sensor elements that detect changes in distal tubular fluid composition and transmit signals to the glomerular vascular elements. This tubuloglomerular feedback mechanism plays an important role in regulating glomerular filtration rate and blood flow. Macula densa cells detect changes in luminal sodium chloride concentration through a complex series of ion transport-related intracellular events. NaCl entry via a Na:K:2Cl cotransporter and Cl exit through a basolateral channel lead to cell depolarization and increases in cytosolic calcium. Na/H exchange (NHE2) results in cell alkalization, whereas intracellular [Na] is regulated by an apically located H(Na)-K ATPase and not by the traditional basolateral Na:K ATPase. Communication from macula densa cells to the glomerular vascular elements involves ATP release across the macula densa basolateral membrane through a maxi-anion channel. The adaptation of multi-photon microscopy is providing new insights into macula densa-glomerular signaling.
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Affiliation(s)
- P Darwin Bell
- Nephrology Research and Training Center, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
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Motoyama HI, Friedman PA. Calcium-sensing receptor regulation of PTH-dependent calcium absorption by mouse cortical ascending limbs. Am J Physiol Renal Physiol 2002; 283:F399-406. [PMID: 12167589 DOI: 10.1152/ajprenal.00346.2001] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Resting Ca(2+) absorption by cortical thick ascending limbs (CALs) is passive and proceeds through the paracellular pathway. In contrast, parathyroid hormone (PTH) stimulates active, transcellular Ca(2+) absorption (J(Ca)). The Ca(2+)-sensing receptor (CaSR) is expressed on serosal membranes of CALs. In the present study, we tested the hypothesis that activation of the CAL CaSR indirectly inhibits passive Ca(2+) transport and directly suppresses PTH-induced cellular J(Ca). To test this theory, we measured J(Ca) and Na absorption (J(Na)) by single perfused mouse CALs. Net absorption was measured microfluorimetrically in samples collected from tubules perfused and bathed in symmetrical HEPES-buffered solutions or those in which luminal Na(+) was reduced from 150 to 50 mM. We first confirmed that Gd(3+) activated the CaSR by measuring intracellular Ca(2+) concentration ([Ca(2+)](i)) in CALs loaded with fura 2. On stepwise addition of Gd(3+) to the bath, [Ca(2+)](i) increased, with a half-maximal rise at 30 microM Gd(3+). J(Ca) and transepithelial voltage (V(e),) were measured in symmetrical Na(+)-containing solutions. PTH increased J(Ca) by 100%, and 30 microM Gd(3+) inhibited this effect. V(e) was unchanged by either PTH or Gd(3+). Similarly, NPS R-467, an organic CaSR agonist, inhibited PTH-stimulated J(Ca) without altering V(e). Neither PTH nor Gd(3+) affected J(Na). Addition of bumetanide to the luminal perfusate abolished J(Na) and V(e). These results show that CaSR activation directly inhibited PTH-induced transcellular J(Ca) and that cellular Ca(2+) and Na(+) transport can be dissociated. To test the effect of CaSR activation on passive paracellular Ca(2+) transport, J(Ca) was measured under asymmetrical Na conditions, in which passive Ca(2+) transport dominates transepithelial absorption. PTH stimulated J(Ca) by 24% and was suppressed by Gd(3+). In this setting, Gd(3+) reduced V(e) by 32%, indicating that CaSR activation inhibited both transcellular and paracellular Ca(2+) transport. We conclude that the CaSR regulates both active transcellular and passive paracellular Ca(2+) reabsorption but has no effect on J(Na) by CALs.
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Affiliation(s)
- Hiroki I Motoyama
- Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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14
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Abstract
Recently, multiphoton excitation fluorescence microscopy has been developed that offers important advantages over confocal imaging, particularly for in vivo visualization of thick tissue samples. We used this state-of-the-art technique to capture high-quality images and study the function of otherwise inaccessible cell types and complex cell structures of the juxtaglomerular apparatus (JGA) in living preparations of the kidney. This structure has multiple cell types that exhibit a complex array of functions, which regulate the process of filtrate formation and renal hemodynamics. We report, for the first time, on high-resolution three-dimensional morphology and Z-sectioning through isolated, perfused kidney glomeruli, tubules, and JGA. Time-series images show how alterations in tubular fluid composition cause striking changes in single-cell volume of the unique macula densa tubular epithelium in situ and how they also affect glomerular filtration through alterations in associated structures within the JGA. In addition, calcium imaging of the glomerulus and JGA demonstrates the utility of this system in capturing the complexity of events and effects that are exerted by the specific hypertensive autacoid angiotensin II. This imaging approach to the study of isolated, perfused live tissue with multiphoton microscopy may be applied to other biological systems in which multiple cell types form a functionally integrated syncytium.
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Affiliation(s)
- János Peti-Peterdi
- Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, Okazaki 444-8585, Japan.
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15
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Peti-Peterdi J, Chambrey R, Bebok Z, Biemesderfer D, St John PL, Abrahamson DR, Warnock DG, Bell PD. Macula densa Na(+)/H(+) exchange activities mediated by apical NHE2 and basolateral NHE4 isoforms. Am J Physiol Renal Physiol 2000; 278:F452-63. [PMID: 10710550 DOI: 10.1152/ajprenal.2000.278.3.f452] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Functional and immunohistochemical studies were performed to localize and identify Na(+)/H(+) exchanger (NHE) isoforms in macula densa cells. By using the isolated perfused thick ascending limb with attached glomerulus preparation dissected from rabbit kidney, intracellular pH (pH(i)) was measured with fluorescence microscopy by using 2',7'-bis-(2-carboxyethyl)-5-(and -6) carboxyfluorescein. NHE activity was assayed by measuring the initial rate of Na(+)-dependent pH(i) recovery from an acid load imposed by prior lumen and bath Na(+) removal. Removal of Na(+) from the bath resulted in a significant, DIDS-insensitive, ethylisopropyl amiloride (EIPA)-inhibitable decrease in pH(i). This basolateral transporter showed very low affinity for EIPA and Hoechst 694 (IC(50) = 9.0 and 247 microM, respectively, consistent with NHE4). The recently reported apical NHE was more sensitive to inhibition by these drugs (IC(50) = 0.86 and 7.6 microM, respectively, consistent with NHE2). Increasing osmolality, a known activator of NHE4, greatly stimulated basolateral NHE. Immunohistochemical studies using antibodies against NHE1-4 peptides demonstrated expression of NHE2 along the apical and NHE4 along the basolateral, membrane, whereas NHE1 and NHE3 were not detected. These results suggest that macula densa cells functionally and immunologically express NHE2 at the apical membrane and NHE4 at the basolateral membrane. These two isoforms likely participate in Na(+) transport, pH(i), and cell volume regulation and may be involved in tubuloglomerular feedback signaling by these cells.
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Affiliation(s)
- J Peti-Peterdi
- Department of Medicine, Division of Nephrology and Nephrology Research and Training Center, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
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16
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Abstract
These studies examine the properties of an apical potassium (K+) channel in macula densa cells, a specialized group of cells involved in tubuloglomerular feedback signal transmission. To this end, individual glomeruli with thick ascending limbs (TAL) and macula densa cells were dissected from rabbit kidney and the TAL covering macula densa cells was removed. Using patch clamp techniques, we found a high density (up to 54 channels per patch) of K+ channels in the apical membrane of macula densa cells. An inward conductance of 41.1 +/- 4.8 pS was obtained in cell-attached patches (patch pipette, 140 mM K+). In inside-out patches (patch pipette, 140 mM; bath, 5 mM K+), inward currents of 1.1 +/- 0.1 pA (n = 11) were observed at 0 mV and single channel current reversed at a pipette potential of -84 mV giving a permeability ratio (PK/PNa) of over 100. In cell-attached patches, mean channel open probability (N,Po, where N is number of channels in the patch and Po is single channel open probability) was unaffected by bumetanide, but was reduced from 11.3 +/- 2.7 to 1.6 +/- 1.3 (n = 5, p < 0.02) by removal of bath sodium (Na+). Simultaneous removal of bath Na+ and calcium (Ca2+) prevented the Na(+)-induced decrease in N.Po indicating that the effect of Na+ removal on N.Po was probably mediated by stimulation of Ca2+ entry. This interpretation was supported by studies where ionomycin, which directly increases intracellular Ca2+, produced a fall in N.Po from 17.8 +/- 4.0 to 5.9 +/- 4.1 (n = 7, p < 0.02). In inside-out patches, the apical K+ channel was not sensitive to ATP but was directly blocked by 2 mM Ca2+ and by lowering bath pH from 7.4 to 6.8. These studies constitute the first single channel observations on macula densa cells and establish some of the characteristics and regulators of this apical K+ channel. This channel is likely to be involved in macula densa transepithelial Cl- transport and perhaps in the tubuloglomerular feedback signaling process.
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Affiliation(s)
- A M Hurst
- Groupe de Recherche en Transport Membranaire, Université de Montréal, Québec
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17
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Abstract
Recent studies have suggested that cytosolic calcium serves in the transmission of signals between distal tubular fluid and glomerular vascular elements. Since cAMP can modify calcium-mediated events, it was of interest to determine if agents that elevate intracellular cAMP could influence feedback responses and to assess the interaction of cAMP and intracellular calcium in the transmission of feedback signals. Stop flow pressure (SFP) was measured in the rat during retrograde microperfusion into the distal tubule at 15 nl/min. SFP averaged 37.5 +/- 0.5 mm Hg and decreased by 12.8 +/- 0.8 mm Hg (N = 44) during perfusion with an isotonic Ringer's solution. Addition of 3-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor, decreased the magnitude of SFP feedback responses; 89 +/- 4.5% (N = 16) inhibition was observed at an IBMX concentration of 500 microM. In addition, SFP decreased by only 3 +/- 1 mm Hg (N = 8) during perfusion with 10 mM dibutyryl cAMP in the presence of a low concentration of IBMX and by 1.6 +/- 0.7 mm Hg (N = 12) during perfusion with forskolin, an agent that stimulates adenylate cyclase activity. Calcium ionophore (A23187) significantly increased the magnitude of SFP feedback responses obtained with IBMX alone from 5 +/- 1.0 mm Hg (N = 9; 250 micron IBMX) to 10 +/- 1.2 mm Hg (N = 11). These results indicate that agents which elevate intracellular cAMP markedly attenuate tubuloglomerular feedback responses and that calcium ionophore can reverse the inhibitory effects of increased cAMP.
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