1
|
Shi Y, Duan H, Liu J, Shi X, Zhao M, Zhang Y. Association of triglyceride glucose index with the risk of acute kidney injury in patients with coronary revascularization: a cohort study. Diabetol Metab Syndr 2024; 16:117. [PMID: 38807249 PMCID: PMC11131318 DOI: 10.1186/s13098-024-01358-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Accepted: 05/21/2024] [Indexed: 05/30/2024] Open
Abstract
BACKGROUND The triglyceride glucose (TyG) index is a novel and reliable alternative marker for insulin resistance. Previous studies have shown that TyG index is closely associated with cardiovascular outcomes in cardiovascular diseases and coronary revascularization. However, the relationship between TyG index and renal outcomes of coronary revascularization is unclear. The purpose of this study was to investigate the correlation between TyG index and the risk of acute kidney injury (AKI) in patients with coronary revascularization. METHODS A retrospective cohort study was conducted to select eligible patients with coronary revascularization admitted to ICU in the medical information mart for intensive care IV (MIMIC-IV). According to the TyG index quartile, these patients were divided into four groups (Q1-Q4). The primary endpoint was the incidence of AKI, and secondary endpoints included 28-day mortality and the rate of renal replacement therapy (RRT) use in the AKI population. Multivariate Cox regression analysis and restricted cubic splines (RCS) were used to analyze TyG index association with AKI risk. Kaplan-Meier survival analysis was performed to assess the incidence of endpoints in the four groups. RESULTS In this study, 790 patients who underwent coronary revascularization surgery were included, and the incidence of AKI was 30.13%. Kaplan-Meier analysis showed that patients with a high TyG index had a significantly increased incidence of AKI (Log-rank P = 0.0045). Multivariate Cox regression analysis showed that whether TyG index was a continuous variable (HR 1.42, 95% CI 1.06-1.92, P = 0.018) or a categorical variable (Q4: HR 1.89, 95% CI 1.12-3.17, P = 0.017), and there was an independent association between TyG index and AKI in patients with coronary revascularization. The RCS curve showed a linear relationship between higher TyG index and AKI in this particular population (P = 0.078). In addition, Kaplan-Meier analysis showed a significantly increased risk of RRT application in a subset of AKI patients based on quartiles of TyG index (P = 0.029). CONCLUSION TyG index was significantly associated with increased risk of AKI and adverse renal outcomes in patients with coronary revascularization. This finding suggests that the TyG index may be useful in identifying people at high risk for AKI and poor renal outcomes in patients with coronary revascularization.
Collapse
Affiliation(s)
- Yue Shi
- Department of Nephrology, Xiyuan Hospital, China Academy of Chinese Medical Sciences, Beijing, 100091, China
| | - Hangyu Duan
- Department of Nephrology, Xiyuan Hospital, China Academy of Chinese Medical Sciences, Beijing, 100091, China
| | - Jing Liu
- Department of Nephrology, Xiyuan Hospital, China Academy of Chinese Medical Sciences, Beijing, 100091, China
- Beijing University of Chinese Medicine, Beijing, 100029, China
| | - Xiujie Shi
- Department of Nephrology, Xiyuan Hospital, China Academy of Chinese Medical Sciences, Beijing, 100091, China
| | - Mingming Zhao
- Department of Nephrology, Xiyuan Hospital, China Academy of Chinese Medical Sciences, Beijing, 100091, China.
| | - Yu Zhang
- Department of Nephrology, Xiyuan Hospital, China Academy of Chinese Medical Sciences, Beijing, 100091, China.
| |
Collapse
|
2
|
Staruschenko A, Ma R, Palygin O, Dryer SE. Ion channels and channelopathies in glomeruli. Physiol Rev 2023; 103:787-854. [PMID: 36007181 PMCID: PMC9662803 DOI: 10.1152/physrev.00013.2022] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 08/15/2022] [Accepted: 08/21/2022] [Indexed: 11/22/2022] Open
Abstract
An essential step in renal function entails the formation of an ultrafiltrate that is delivered to the renal tubules for subsequent processing. This process, known as glomerular filtration, is controlled by intrinsic regulatory systems and by paracrine, neuronal, and endocrine signals that converge onto glomerular cells. In addition, the characteristics of glomerular fluid flow, such as the glomerular filtration rate and the glomerular filtration fraction, play an important role in determining blood flow to the rest of the kidney. Consequently, disease processes that initially affect glomeruli are the most likely to lead to end-stage kidney failure. The cells that comprise the glomerular filter, especially podocytes and mesangial cells, express many different types of ion channels that regulate intrinsic aspects of cell function and cellular responses to the local environment, such as changes in glomerular capillary pressure. Dysregulation of glomerular ion channels, such as changes in TRPC6, can lead to devastating glomerular diseases, and a number of channels, including TRPC6, TRPC5, and various ionotropic receptors, are promising targets for drug development. This review discusses glomerular structure and glomerular disease processes. It also describes the types of plasma membrane ion channels that have been identified in glomerular cells, the physiological and pathophysiological contexts in which they operate, and the pathways by which they are regulated and dysregulated. The contributions of these channels to glomerular disease processes, such as focal segmental glomerulosclerosis (FSGS) and diabetic nephropathy, as well as the development of drugs that target these channels are also discussed.
Collapse
Affiliation(s)
- Alexander Staruschenko
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida
- Hypertension and Kidney Research Center, University of South Florida, Tampa, Florida
- James A. Haley Veterans Hospital, Tampa, Florida
| | - Rong Ma
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
| | - Oleg Palygin
- Division of Nephrology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Stuart E Dryer
- Department of Biology and Biochemistry, University of Houston, Houston, Texas
- Department of Biomedical Sciences, Tilman J. Fertitta Family College of Medicine, University of Houston, Houston, Texas
| |
Collapse
|
3
|
Hu S, Han R, Chen L, Qin W, Xu X, Shi J, Zhu X, Zhang M, Zeng C, Tang Z, Bao H, Liu Z. Upregulated LRRC55 promotes BK channel activation and aggravates cell injury in podocytes. J Exp Med 2021; 218:e20192373. [PMID: 33346797 PMCID: PMC7756252 DOI: 10.1084/jem.20192373] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 07/27/2020] [Accepted: 09/16/2020] [Indexed: 12/15/2022] Open
Abstract
Podocyte injury is a common hallmark in various glomerular diseases. The level of LRRC55 was increased in podocytes of patients with focal segmental glomerulosclerosis (FSGS), diabetic nephropathy (DN), and membranous nephropathy (MN). Upregulated LRRC55 and increased intracellular Ca2+ led to BK channel activation and the loss of intracellular potassium, resulting in apoptosome formation and caspase-3 activation in angiotensin II (Ang II)-treated podocytes. Knockout of Lrrc55 or the BK channel prevented the BK current and ameliorated podocyte injury in Ang II-treated mice. Upstream, NFATc3 regulated the expression of LRRC55. Increased LRRC55 expression in podocytes was also evident in animal models of FSGS, DN, and MN. Treatment with losartan or LRRC55 siRNA suppressed LRRC55 expression, prevented BK channel activation, and attenuated podocyte injury in animal models of FSGS, DN, and MN. In conclusion, upregulated LRRC55 promotes BK channel activation and aggravates cell injury in podocytes in FSGS, DN, and MN. LRRC55 inhibition may represent a new therapeutic approach for podocyte injury.
Collapse
Affiliation(s)
- Shuai Hu
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China
| | - Runhong Han
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China
| | - Long Chen
- National Standard Laboratory of Pharmacology for Chinese Materia Medica, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Weisong Qin
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China
| | - Xiaodong Xu
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China
| | - Jingsong Shi
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China
| | - Xiaodong Zhu
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China
| | - Mingchao Zhang
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China
| | - Caihong Zeng
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China
| | - Zheng Tang
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China
| | - Hao Bao
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China
| | - Zhihong Liu
- National Clinical Research Center of Kidney Diseases, Jinling Hospital, Nanjing University School of Medicine, Nanjing, China
| |
Collapse
|
4
|
Binz-Lotter J, Jüngst C, Rinschen MM, Koehler S, Zentis P, Schauss A, Schermer B, Benzing T, Hackl MJ. Injured Podocytes Are Sensitized to Angiotensin II-Induced Calcium Signaling. J Am Soc Nephrol 2020; 31:532-542. [PMID: 31924670 DOI: 10.1681/asn.2019020109] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 12/01/2019] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND Inhibition of angiotensin II (AngII) signaling, a therapeutic mainstay of glomerular kidney diseases, is thought to act primarily through regulating glomerular blood flow and reducing filtration pressure. Although extravascular actions of AngII have been suggested, a direct effect of AngII on podocytes has not been demonstrated in vivo. METHODS To study the effects of AngII on podocyte calcium levels in vivo, we used intravital microscopy of the kidney in mice expressing the calcium indicator protein GCaMP3. RESULTS In healthy animals, podocytes displayed limited responsiveness to AngII stimulation. In contrast, in animals subjected to either adriamycin-induced acute chemical injury or genetic deletion of the podocin-encoding gene Nphs2, the consequent podocyte damage and proteinuria rendered the cells responsive to AngII and resulted in AngII-induced calcium transients in significantly more podocytes. The angiotensin type 1 receptor blocker losartan could fully inhibit this response. Also, responsiveness to AngII was at least partly mediated through the transient receptor potential channel 6, which has been implicated in podocyte calcium handling. Interestingly, loss of a single Nphs2 allele also increased podocytes' responsiveness to AngII signaling. This direct effect of AngII on injured podocytes results in increased calcium transients, which can further aggravate the underlying kidney disease. CONCLUSIONS Our discovery that podocytes become sensitized to AngII-induced calcium signaling upon injury might explain results from large, randomized, controlled trials in which improved renal outcomes occur only in the subgroup of patients with proteinuria, indicating podocyte damage. Our findings also emphasize the need to treat every patient with a glomerular disease with either an angiotensin-converting enzyme inhibitor or an angiotensin type 1 receptor blocker.
Collapse
Affiliation(s)
- Julia Binz-Lotter
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; and
| | - Christian Jüngst
- Cologne Excellence Cluster on Cellular Stress Response in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Markus M Rinschen
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; and
| | - Sybille Koehler
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; and
| | - Peter Zentis
- Cologne Excellence Cluster on Cellular Stress Response in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Astrid Schauss
- Cologne Excellence Cluster on Cellular Stress Response in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Bernhard Schermer
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; and.,Cologne Excellence Cluster on Cellular Stress Response in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Thomas Benzing
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; and.,Cologne Excellence Cluster on Cellular Stress Response in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Matthias J Hackl
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; and
| |
Collapse
|
5
|
Inoue K, Tian X, Velazquez H, Soda K, Wang Z, Pedigo CE, Wang Y, Cross E, Groener M, Shin JW, Li W, Hassan H, Yamamoto K, Mundel P, Ishibe S. Inhibition of Endocytosis of Clathrin-Mediated Angiotensin II Receptor Type 1 in Podocytes Augments Glomerular Injury. J Am Soc Nephrol 2019; 30:2307-2320. [PMID: 31511362 PMCID: PMC6900791 DOI: 10.1681/asn.2019010053] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 08/04/2019] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Inhibition of the renin-angiotensin system remains a cornerstone in reducing proteinuria and progression of kidney failure, effects believed to be the result of reduction in BP and glomerular hyperfiltration. However, studies have yielded conflicting results on whether podocyte-specific angiotensin II (AngII) signaling directly induces podocyte injury. Previous research has found that after AngII stimulation, β-arrestin-bound angiotensin II receptor type 1 (AT1R) is internalized in a clathrin- and dynamin-dependent manner, and that Dynamin1 and Dynamin2 double-knockout mice exhibit impaired clathrin-mediated endocytosis. METHODS We used podocyte-specific Dyn double-knockout mice to examine AngII-stimulated AT1R internalization and signaling in primary podocytes and controls. We also examined the in vivo effect of AngII in these double-knockout mice through renin-angiotensin system blockers and through deletion of Agtr1a (which encodes the predominant AT1R isoform expressed in kidney, AT1aR). We tested calcium influx, Rac1 activation, and lamellipodial extension in control and primary podocytes of Dnm double-knockout mice treated with AngII. RESULTS We confirmed augmented AngII-stimulated AT1R signaling in primary Dnm double-knockout podocytes resulting from arrest of clathrin-coated pit turnover. Genetic ablation of podocyte Agtr1a in Dnm double-knockout mice demonstrated improved albuminuria and kidney function compared with the double-knockout mice. Isolation of podocytes from Dnm double-knockout mice revealed abnormal membrane dynamics, with increased Rac1 activation and lamellipodial extension, which was attenuated in Dnm double-knockout podocytes lacking AT1aR. CONCLUSIONS Our results indicate that inhibiting aberrant podocyte-associated AT1aR signaling pathways has a protective effect in maintaining the integrity of the glomerular filtration barrier.
Collapse
Affiliation(s)
- Kazunori Inoue
- Section of Nephrology, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
| | - Xuefei Tian
- Section of Nephrology, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
| | - Heino Velazquez
- Section of Nephrology, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
| | - Keita Soda
- Section of Nephrology, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
| | - Zhen Wang
- Section of Nephrology, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
| | - Christopher E Pedigo
- Section of Nephrology, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
| | - Ying Wang
- Section of Nephrology, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
| | - Elizabeth Cross
- Section of Nephrology, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
| | - Marwin Groener
- Section of Nephrology, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
| | - Jee-Won Shin
- Section of Nephrology, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
| | - Wei Li
- Section of Nephrology, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
| | - Hossam Hassan
- Section of Nephrology, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
| | - Koichi Yamamoto
- Department of Geriatric Medicine, Osaka University Graduate School of Medicine, Suita, Osaka, Japan; and
| | - Peter Mundel
- Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
| | - Shuta Ishibe
- Section of Nephrology, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut;
| |
Collapse
|
6
|
Molecular Mechanisms of Kidney Injury and Repair in Arterial Hypertension. Int J Mol Sci 2019; 20:ijms20092138. [PMID: 31052201 PMCID: PMC6539752 DOI: 10.3390/ijms20092138] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 04/25/2019] [Accepted: 04/28/2019] [Indexed: 02/06/2023] Open
Abstract
The global burden of chronic kidney disease is rising. The etiologies, heterogeneous, and arterial hypertension, are key factors contributing to the development and progression of chronic kidney disease. Arterial hypertension is induced and maintained by a complex network of systemic signaling pathways, such as the hormonal axis of the renin-angiotensin-aldosterone system, hemodynamic alterations affecting blood flow, oxygen supply, and the immune system. This review summarizes the clinical and histopathological features of hypertensive kidney injury and focusses on the interplay of distinct systemic signaling pathways, which drive hypertensive kidney injury in distinct cell types of the kidney. There are several parallels between hypertension-induced molecular signaling cascades in the renal epithelial, endothelial, interstitial, and immune cells. Angiotensin II signaling via the AT1R, hypoxia induced HIFα activation and mechanotransduction are closely interacting and further triggering the adaptions of metabolism, cytoskeletal rearrangement, and profibrotic TGF signaling. The interplay of these, and other cellular pathways, is crucial to balancing the injury and repair of the kidneys and determines the progression of hypertensive kidney disease.
Collapse
|
7
|
Schenk LK, Ousingsawat J, Skryabin BV, Schreiber R, Pavenstädt H, Kunzelmann K. Regulation and Function of TMEM16F in Renal Podocytes. Int J Mol Sci 2018; 19:ijms19061798. [PMID: 29912162 PMCID: PMC6032267 DOI: 10.3390/ijms19061798] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Revised: 06/12/2018] [Accepted: 06/14/2018] [Indexed: 12/13/2022] Open
Abstract
The Ca2+-activated phospholipid scramblase and ion channel TMEM16F is expressed in podocytes of renal glomeruli. Podocytes are specialized cells that form interdigitating foot processes as an essential component of the glomerular filter. These cells, which participate in generation of the primary urine, are often affected during primary glomerular diseases, such as glomerulonephritis and secondary hypertensive or diabetic nephropathy, which always leads to proteinuria. Because the function of podocytes is known to be controlled by intracellular Ca2+ signaling, it is important to know about the role of Ca2+-activated TMEM16F in these cells. To that end, we generated an inducible TMEM16F knockdown in the podocyte cell line AB8, and produced a conditional mouse model with knockout of TMEM16F in podocytes and renal epithelial cells of the nephron. We found that knockdown of TMEM16F did not produce proteinuria or any obvious phenotypic changes. Knockdown of TMEM16F affected cell death of tubular epithelial cells but not of glomerular podocytes when analyzed in TUNEL assays. Surprisingly, and in contrast to other cell types, TMEM16F did not control intracellular Ca2+ signaling and was not responsible for Ca2+-activated whole cell currents in podocytes. TMEM16F levels in podocytes were enhanced after inhibition of the endolysosomal pathway and after treatment with angiotensin II. Renal knockout of TMEM16F did not compromise renal morphology and serum electrolytes. Taken together, in contrast to other cell types, such as platelets, bone cells, and immune cells, TMEM16F shows little effect on basal properties of podocytes and does not appear to be essential for renal function.
Collapse
Affiliation(s)
- Laura K Schenk
- Department of Nephrology, Hypertension and Rheumatology, University Hospital Muenster, 48149 Muenster, Germany.
| | - Jiraporn Ousingsawat
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany.
| | - Boris V Skryabin
- Transgenic Animal and Genetic Engineering Models (TRAM), Department of Medicine, Westfälischen, Wilhelms⁻Universität Münster, 48149 Münster, Germany.
| | - Rainer Schreiber
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany.
| | - Hermann Pavenstädt
- Department of Nephrology, Hypertension and Rheumatology, University Hospital Muenster, 48149 Muenster, Germany.
| | - Karl Kunzelmann
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany.
| |
Collapse
|
8
|
Höhne M, Frese CK, Grahammer F, Dafinger C, Ciarimboli G, Butt L, Binz J, Hackl MJ, Rahmatollahi M, Kann M, Schneider S, Altintas MM, Schermer B, Reinheckel T, Göbel H, Reiser J, Huber TB, Kramann R, Seeger-Nukpezah T, Liebau MC, Beck BB, Benzing T, Beyer A, Rinschen MM. Single-nephron proteomes connect morphology and function in proteinuric kidney disease. Kidney Int 2018; 93:1308-1319. [PMID: 29530281 DOI: 10.1016/j.kint.2017.12.012] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 12/01/2017] [Accepted: 12/14/2017] [Indexed: 12/25/2022]
Abstract
In diseases of many parenchymatous organs, heterogeneous deterioration of individual functional units determines the clinical prognosis. However, the molecular characterization at the level of such individual subunits remains a technological challenge that needs to be addressed in order to better understand pathological mechanisms. Proteinuric glomerular kidney diseases are frequent and assorted diseases affecting a fraction of glomeruli and their draining tubules to variable extents, and for which no specific treatment exists. Here, we developed and applied a mass spectrometry-based methodology to investigate heterogeneity of proteomes from individually isolated nephron segments from mice with proteinuric kidney disease. In single glomeruli from two different mouse models of sclerotic glomerular disease, we identified a coherent protein expression module consisting of extracellular matrix protein deposition (reflecting glomerular sclerosis), glomerular albumin (reflecting proteinuria) and LAMP1, a lysosomal protein. This module was associated with a loss of podocyte marker proteins while genetic ablation of LAMP1-correlated lysosomal proteases could ameliorate glomerular damage in vivo. Furthermore, proteomic analyses of individual glomeruli from patients with genetic sclerotic and non-sclerotic proteinuric diseases revealed increased abundance of lysosomal proteins, in combination with a decreased abundance of mutated gene products. Thus, altered protein homeostasis (proteostasis) is a conserved key mechanism in proteinuric kidney diseases. Moreover, our technology can capture intra-individual variability in diseases of the kidney and other tissues at a sub-biopsy scale.
Collapse
Affiliation(s)
- Martin Höhne
- Department II of Internal Medicine, University of Cologne, Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany; Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Cologne, Germany
| | - Christian K Frese
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Florian Grahammer
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Department of Medicine IV, Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Claudia Dafinger
- Department II of Internal Medicine, University of Cologne, Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany; Department of Pediatrics, Division of Pediatric Nephrology, University Hospital of Cologne, Cologne, Germany
| | | | - Linus Butt
- Department II of Internal Medicine, University of Cologne, Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
| | - Julia Binz
- Department II of Internal Medicine, University of Cologne, Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
| | - Matthias J Hackl
- Department II of Internal Medicine, University of Cologne, Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
| | - Mahdieh Rahmatollahi
- Department II of Internal Medicine, University of Cologne, Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
| | - Martin Kann
- Department II of Internal Medicine, University of Cologne, Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
| | - Simon Schneider
- Department of Medicine IV, Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Bernhard Schermer
- Department II of Internal Medicine, University of Cologne, Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany; Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Cologne, Germany
| | - Thomas Reinheckel
- Institut of Molecular Medicine and Cell Research, Faculty of Medicine, University of Freiburg, Freiburg, Germany; BIOSS Centre for Biological Signalling Studies and Center for Biological Systems Analysis (ZBSA), Albert-Ludwigs-University, Freiburg, Germany
| | - Heike Göbel
- Institute of Pathology, University Hospital Cologne, Cologne, Germany
| | - Jochen Reiser
- Rush University Medical Center, Chicago, Illinois, USA
| | - Tobias B Huber
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Department of Medicine IV, Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany; BIOSS Centre for Biological Signalling Studies and Center for Biological Systems Analysis (ZBSA), Albert-Ludwigs-University, Freiburg, Germany
| | - Rafael Kramann
- Division of Nephrology, RWTH Aachen University, Aachen, Germany
| | | | - Max C Liebau
- Department II of Internal Medicine, University of Cologne, Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany; Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Cologne, Germany; Department of Pediatrics, Division of Pediatric Nephrology, University Hospital of Cologne, Cologne, Germany
| | - Bodo B Beck
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany; Department of Human Genetics, University Hospital Cologne, Cologne, Germany
| | - Thomas Benzing
- Department II of Internal Medicine, University of Cologne, Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany; Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Cologne, Germany
| | - Andreas Beyer
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany; Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Cologne, Germany
| | - Markus M Rinschen
- Department II of Internal Medicine, University of Cologne, Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany; Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Cologne, Germany.
| |
Collapse
|
9
|
Actin dynamics at focal adhesions: a common endpoint and putative therapeutic target for proteinuric kidney diseases. Kidney Int 2018; 93:1298-1307. [PMID: 29678354 DOI: 10.1016/j.kint.2017.12.028] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 12/07/2017] [Accepted: 12/13/2017] [Indexed: 01/02/2023]
Abstract
Proteinuria encompasses diverse causes including both genetic diseases and acquired forms such as diabetic and hypertensive nephropathy. The basis of proteinuria is a disturbance in size selectivity of the glomerular filtration barrier, which largely depends on the podocyte: a terminally differentiated epithelial cell type covering the outer surface of the glomerulus. Compromised podocyte structure is one of the earliest signs of glomerular injury. The phenotype of diverse animal models and podocyte cell culture firmly established the essential role of the actin cytoskeleton in maintaining functional podocyte structure. Podocyte foot processes, actin-based membrane extensions, contain 2 molecularly distinct "hubs" that control actin dynamics: a slit diaphragm and focal adhesions. Although loss of foot processes encompasses disassembly of slit diaphragm multiprotein complexes, as long as cells are attached to the glomerular basement membrane, focal adhesions will be the sites in which stress due to filtration flow is counteracted by forces generated by the actin network in foot processes. Numerous studies within last 20 years have identified actin binding and regulatory proteins as well as integrins as essential components of signaling and actin dynamics at focal adhesions in podocytes, suggesting that some of them may become novel, druggable targets for proteinuric kidney diseases. Here we review evidence supporting the idea that current treatments for chronic kidney diseases beneficially and directly target the podocyte actin cytoskeleton associated with focal adhesions and suggest that therapeutic reagents that target the focal adhesion-regulated actin cytoskeleton in foot processes have potential to modernize treatments for chronic kidney diseases.
Collapse
|
10
|
Dupont V, Debrumetz A, Wynckel A, Rieu P. [How to explain glomerular filtration rate decrease in intra-abdominal hypertension?]. Nephrol Ther 2017; 14:24-28. [PMID: 29173983 DOI: 10.1016/j.nephro.2017.04.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/02/2017] [Accepted: 04/04/2017] [Indexed: 11/19/2022]
Abstract
Intra-abdominal hypertension (IAH) is a frequent and serious condition affecting critical care patients. IAH diagnostic needs intravesical pressure (IVP) measurement which is recommended for monitoring patients presenting IAH risk factors. IVP monitoring is probably insufficient in daily practice. This could be explained by lack of knowledge about IAH physiopathology, which leads to absence of therapeutic target. Acute kidney injury (AKI) is the earliest and most described organ dysfunction associated with IAH. Moreover, AKI gravity seems to correlates with IAH severity. Physiopathological aspects explaining glomerular filtration rate (GFR) decrease with IAH are probably multifactorial and not completely understood. The role of renal venous congestion is essential to explain AKI in IAH. GFR decrease may reflect a "glomerular capillary shunt" due to a decrease of renal plasmatic flow. Monitoring IVP in daily practice in patients presenting risk factors of IAH would improve knowledge about this condition and the associated AKI.
Collapse
Affiliation(s)
- Vincent Dupont
- Service de néphrologie, CHU de Reims, 45, rue Cognacq-Jay, 51092 Reims cedex, France.
| | - Alexandre Debrumetz
- Service de néphrologie, CHU de Reims, 45, rue Cognacq-Jay, 51092 Reims cedex, France
| | - Alain Wynckel
- Service de néphrologie, CHU de Reims, 45, rue Cognacq-Jay, 51092 Reims cedex, France
| | - Philippe Rieu
- Service de néphrologie, CHU de Reims, 45, rue Cognacq-Jay, 51092 Reims cedex, France
| |
Collapse
|
11
|
Schenk LK, Möller-Kerutt A, Klosowski R, Wolters D, Schaffner-Reckinger E, Weide T, Pavenstädt H, Vollenbröker B. Angiotensin II regulates phosphorylation of actin-associated proteins in human podocytes. FASEB J 2017; 31:5019-5035. [PMID: 28768720 DOI: 10.1096/fj.201700142r] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 07/17/2017] [Indexed: 02/02/2023]
Abstract
Within the kidney, angiotensin II (AngII) targets different cell types in the vasculature, tubuli, and glomeruli. An important part of the renal filtration barrier is composed of podocytes with their actin-rich foot processes. In this study, we used stable isotope labeling with amino acids in cell culture coupled to mass spectrometry to characterize relative changes in the phosphoproteome of human podocytes in response to short-term treatment with AngII. In 4 replicates, we identified a total of 17,956 peptides that were traceable to 2081 distinct proteins. Bioinformatic analyses revealed that among the increasingly phosphorylated peptides are predominantly peptides that are related to actin filaments, cytoskeleton, lamellipodia, mammalian target of rapamycin, and MAPK signaling. Among others, this screening approach highlighted the increased phosphorylation of actin-bundling protein, l-plastin (LCP1). AngII-dependent phosphorylation of LCP1 in cultured podocytes was mediated by the kinases ERK, p90 ribosomal S6 kinase, PKA, or PKC. LCP1 phosphorylation increased filopodia formation. In addition, treatment with AngII led to LCP1 redistribution to the cell margins, membrane ruffling, and formation of lamellipodia. Our data highlight the importance of AngII-triggered actin cytoskeleton-associated signal transduction in podocytes.-Schenk, L. K., Möller-Kerutt, A., Klosowski, R., Wolters, D., Schaffner-Reckinger, E., Weide, T., Pavenstädt, H., Vollenbröker, B. Angiotensin II regulates phosphorylation of actin-associated proteins in human podocytes.
Collapse
Affiliation(s)
- Laura K Schenk
- Medizinischen Klinik und Poliklinik D, Universitätsklinikum Münster, Munster, Germany
| | - Annika Möller-Kerutt
- Medizinischen Klinik und Poliklinik D, Universitätsklinikum Münster, Munster, Germany
| | - Rafael Klosowski
- Analytische Chemie, Biomolekulare Massenspektrometrie, Ruhr-Universität Bochum, Bochum, Germany
| | - Dirk Wolters
- Analytische Chemie, Biomolekulare Massenspektrometrie, Ruhr-Universität Bochum, Bochum, Germany
| | - Elisabeth Schaffner-Reckinger
- Laboratory of Cytoskeleton and Cell Plasticity, Life Sciences Research Unit, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Thomas Weide
- Medizinischen Klinik und Poliklinik D, Universitätsklinikum Münster, Munster, Germany
| | - Hermann Pavenstädt
- Medizinischen Klinik und Poliklinik D, Universitätsklinikum Münster, Munster, Germany
| | - Beate Vollenbröker
- Medizinischen Klinik und Poliklinik D, Universitätsklinikum Münster, Munster, Germany;
| |
Collapse
|
12
|
Podocyte directed therapy of nephrotic syndrome-can we bring the inside out? Pediatr Nephrol 2016; 31:393-405. [PMID: 25939817 DOI: 10.1007/s00467-015-3116-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 04/08/2015] [Accepted: 04/09/2015] [Indexed: 12/15/2022]
Abstract
Several of the drugs currently used for the treatment of glomerular diseases are prescribed for their immunotherapeutic or anti-inflammatory properties, based on the current understanding that glomerular diseases are mediated by immune responses. In recent years our understanding of podocytic signalling pathways and the crucial role of genetic predispositions in the pathology of glomerular diseases has broadened. Delineation of those signalling pathways supports the hypothesis that several of the medications and immunosuppressive agents used to treat glomerular diseases directly target glomerular podocytes. Several central downstream signalling pathways merge into regulatory pathways of the podocytic actin cytoskeleton and its connection to the slit diaphragm. The slit diaphragm and the cytoskeleton of the foot process represent a functional unit. A breakdown of the cytoskeletal backbone of the foot processes leads to internalization of slit diaphragm molecules, and internalization of slit diaphragm components in turn negatively affects cytoskeletal signalling pathways. Podocytes display a remarkable ability to recover from complete effacement and to re-form interdigitating foot processes and intact slit diaphragms after pharmacological intervention. This ability indicates an active inside-out signalling machinery which stabilizes integrin complex formations and triggers the recycling of slit diaphragm molecules from intracellular compartments to the cell surface. In this review we summarize current evidence from patient studies and model organisms on the direct impact of immunosuppressive and supportive drugs on podocyte signalling pathways. We highlight new therapeutic targets that may open novel opportunities to enhance and stabilize inside-out pathways in podocytes.
Collapse
|
13
|
Ilatovskaya DV, Palygin O, Levchenko V, Staruschenko A. Single-channel Analysis and Calcium Imaging in the Podocytes of the Freshly Isolated Glomeruli. J Vis Exp 2015:e52850. [PMID: 26167808 DOI: 10.3791/52850] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Podocytes (renal glomerular epithelial cells) are known to regulate glomerular permeability and maintain glomerular structure; a key role for these cells in the pathogenesis of various renal diseases has been established since podocyte injury leads to proteinuria and foot process effacement. It was previously reported that various endogenous agents may cause a dramatic overload in intracellular Ca(2+) concentration in podocytes, presumably leading to albuminuria, and this likely occurs via calcium-conducting ion channels. Therefore, it appeared important to study calcium handling in the podocytes both under normal conditions and in various pathological states. However, available experimental approaches have remained somewhat limited to cultured and transfected cells. Although they represent a good basic model for such studies, they are essentially extracted from the native environment of the glomerulus. Here we describe the methodology of studying podocytes as a part of the freshly isolated whole glomerulus. This preparation retains the functional potential of the podocytes, which are still attached to the capillaries; therefore, podocytes remain in the environment that conserves the major parts of the glomeruli filtration apparatus. The present manuscript elaborates on two experimental approaches that allow 1) real-time detection of calcium concentration changes with the help of ratiometric confocal fluorescence microscopy, and 2) the recording of the single ion channels activity in the podocytes of the freshly isolated glomeruli. These methodologies utilize the advantages of the native environment of the glomerulus that enable researchers to resolve acute changes in the intracellular calcium handling in response to applications of various agents, measure basal concentration of calcium within the cells (for instance, to evaluate disease progression), and assess and manipulate calcium conductance at the level of single ion channels.
Collapse
Affiliation(s)
| | - Oleg Palygin
- Department of Physiology, Medical College of Wisconsin
| | | | | |
Collapse
|
14
|
Schießl IM, Kattler V, Castrop H. In Vivo Visualization of the Antialbuminuric Effects of the Angiotensin-Converting Enzyme Inhibitor Enalapril. J Pharmacol Exp Ther 2015; 353:299-306. [DOI: 10.1124/jpet.114.222125] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
15
|
Rinschen MM, Pahmeyer C, Pisitkun T, Schnell N, Wu X, Maaß M, Bartram MP, Lamkemeyer T, Schermer B, Benzing T, Brinkkoetter PT. Comparative phosphoproteomic analysis of mammalian glomeruli reveals conserved podocin C-terminal phosphorylation as a determinant of slit diaphragm complex architecture. Proteomics 2015; 15:1326-31. [PMID: 25420462 DOI: 10.1002/pmic.201400235] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 09/10/2014] [Accepted: 11/20/2014] [Indexed: 11/06/2022]
Abstract
Glomerular biology is dependent on tightly controlled signal transduction networks that control phosphorylation of signaling proteins such as cytoskeletal regulators or slit diaphragm proteins of kidney podocytes. Cross-species comparison of phosphorylation events is a powerful mean to functionally prioritize and identify physiologically meaningful phosphorylation sites. Here, we present the result of phosphoproteomic analyses of cow and rat glomeruli to allow cross-species comparisons. We discovered several phosphorylation sites with potentially high biological relevance, e.g. tyrosine phosphorylation of the cytoskeletal regulator synaptopodin and the slit diaphragm protein neph-1 (Kirrel). Moreover, cross-species comparisons revealed conserved phosphorylation of the slit diaphragm protein nephrin on an acidic cluster at the intracellular terminus and conserved podocin phosphorylation on the very carboxyl terminus of the protein. We studied a highly conserved podocin phosphorylation site in greater detail and show that phosphorylation regulates affinity of the interaction with nephrin and CD2AP. Taken together, these results suggest that species comparisons of phosphoproteomic data may reveal regulatory principles in glomerular biology. All MS data have been deposited in the ProteomeXchange with identifier PXD001005 (http://proteomecentral.proteomexchange.org/dataset/PXD001005).
Collapse
Affiliation(s)
- Markus M Rinschen
- Department II of Internal Medicine and Center for Molecular Medicine, University of Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany; Systems Biology of Ageing Cologne (Sybacol), University of Cologne, Cologne, Germany
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
The Hippo pathway is controlled by Angiotensin II signaling and its reactivation induces apoptosis in podocytes. Cell Death Dis 2014; 5:e1519. [PMID: 25393475 PMCID: PMC4260734 DOI: 10.1038/cddis.2014.476] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 10/02/2014] [Accepted: 10/03/2014] [Indexed: 01/10/2023]
Abstract
The Hippo pathway fulfills a crucial function in controlling the balance between proliferation, differentiation and apoptosis in cells. Recent studies showed that G protein-coupled receptors (GPCRs) serve as upstream regulators of Hippo signaling, that either activate or inactivate the Hippo pathway via the large tumor suppressor kinase (LATS) and its substrate, the co-transcription factor Yes-associated protein (YAP). In this study, we focused on the Angiotensin II type 1 receptor (AT1R), which belongs to the GPCR family and has an essential role in the control of blood pressure and water homeostasis. We found that Angiotensin II (Ang II) inactivates the pathway by decreasing the activity of LATS kinase; therefore, leading to an enhanced nuclear shuttling of unphosphorylated YAP in HEK293T cells. This shuttling of YAP is actin-dependent as disruption of the actin cytoskeleton inhibited dephosphorylation of LATS and YAP. Interestingly, in contrast to HEK293T cells, podocytes, which are a crucial component of the glomerular filtration barrier, display a predominant nuclear YAP localization in vivo and in vitro. Moreover, stimulation with Ang II did not alter Hippo pathway activity in podocytes, which show a deactivated pathway. Reactivation of the LATS kinase activity in podocytes resulted in an increased cytoplasmic YAP localization accompanied by a strong induction of apoptosis. Thus, our work indicates that the control of LATS activation and subsequent YAP localization is important for podocyte homeostasis and survival.
Collapse
|
17
|
Gao N, Wang H, Zhang X, Yang Z. The inhibitory effect of angiotensin II on BKCa channels in podocytes via oxidative stress. Mol Cell Biochem 2014; 398:217-22. [PMID: 25234195 DOI: 10.1007/s11010-014-2221-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Accepted: 09/13/2014] [Indexed: 01/11/2023]
Abstract
Angiotensin II (Ang II) is an important active substance of the renin-angiotensin system (RAS). The present study has confirmed that abnormalities of Ang II may be related with cerebrovascular diseases, endocrine diseases, cardiovascular diseases, liver diseases, such as: cerebral hypoxia, diabetes, obesity, atrial fibrillation, and liver cirrhosis. However, understanding effects of Ang II on podocytes is not enough. This study was to investigate the effects of oxidative stress on the large conductance, Ca(2+)-activated K(+) channels (BKCa). Results from the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay showed that Ang II induced podocyte death in a concentration-dependent manner. The measurement of superoxide dismutase (SOD) generation demonstrated that Ang II decreased the total SOD of cellular levels. Meaningfully, pretreatment of a type of ROS scavenger formulations named N-(mercaptopropionyl)-glycine (N-MPG) could inhibit podocyte apoptosis induced by Ang II. Meanwhile, patch-clamp technique was used in this study to detect the effects of Ang II on currents of BKCa channel in podocytes. The results indicated that Ang II inhibited the current amplitude of BKCa channel and decreased the slope of I-V curve. Ang II also made the activation curves of BKCa channel shift to the left. These results may provide a theoretical basis for potential treatment of chronic glomerular disease in the future.
Collapse
Affiliation(s)
- Na Gao
- School of Medicine, State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Tumor Microenvironment and Neurovascular Regulation, Nankai University, Tianjin, 300071, China
| | | | | | | |
Collapse
|
18
|
Ilatovskaya DV, Palygin O, Chubinskiy-Nadezhdin V, Negulyaev YA, Ma R, Birnbaumer L, Staruschenko A. Angiotensin II has acute effects on TRPC6 channels in podocytes of freshly isolated glomeruli. Kidney Int 2014; 86:506-14. [PMID: 24646854 PMCID: PMC4149864 DOI: 10.1038/ki.2014.71] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 12/18/2013] [Accepted: 01/16/2014] [Indexed: 12/16/2022]
Abstract
A key role for podocytes in the pathogenesis of proteinuric renal diseases has
been established. Angiotensin II causes depolarization and increased intracellular calcium
concentration in podocytes; members of the cation TRPC channels family, particularly
TRPC6, are proposed as proteins responsible for calcium flux. Angiotensin II evokes
calcium transient through TRPC channels and mutations in the gene encoding the TRPC6
channel result in the development of focal segmental glomerulosclerosis. Here we examined
the effects of angiotensin II on intracellular calcium ion levels and endogenous channels
in intact podocytes of freshly isolated decapsulated mouse glomeruli. An ion channel with
distinct TRPC6 properties was identified in wild type, but was absent in TRPC6 knockout
mice. Single channel electrophysiological analysis found that angiotensin II acutely
activated native TRPC-like channels in both podocytes of freshly isolated glomeruli and
TRPC6 channels transiently overexpressed in CHO cells; the effect was mediated by changes
in the channel open probability. Angiotensin II evoked intracellular calcium transients in
the wild type podocytes, which was blunted in TRPC6 knockout glomeruli. Pan-TRPC inhibitors
gadolinium and SKF 96365 reduced the response in wild type glomerular epithelial cells,
whereas the transient in TRPC6 knockout animals was not affected. Thus, angiotensin
II-dependent activation of TRPC6 channels in podocytes may have a significant role in the
development of kidney diseases.
Collapse
Affiliation(s)
- Daria V Ilatovskaya
- 1] Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA [2] Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russian Federation
| | - Oleg Palygin
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | | | - Yuri A Negulyaev
- 1] Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russian Federation [2] Department of Medical Physics, St. Petersburg State Polytechnical University, St. Petersburg, Russian Federation
| | - Rong Ma
- Department of Integrative Physiology and Cardiovascular Research Institute, University of North Texas Health Science Center, Fort Worth, Texas, USA
| | - Lutz Birnbaumer
- Transmembrane Signaling Group, National Institutes of Health, Research Triangle Park, North Carolina, USA
| | | |
Collapse
|
19
|
Anderson M, Roshanravan H, Khine J, Dryer SE. Angiotensin II activation of TRPC6 channels in rat podocytes requires generation of reactive oxygen species. J Cell Physiol 2014; 229:434-42. [PMID: 24037962 DOI: 10.1002/jcp.24461] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 08/27/2013] [Indexed: 11/06/2022]
Abstract
Angiotensin II (AII) plays a major role in the progression of chronic kidney diseases. Podocytes are essential components of the ultrafiltration apparatus, and are targets for AII signaling. AII has been shown to increase generation of reactive oxygen species (ROS) in podocytes. Canonical transient receptor potential-6 (TRPC6) channels stimulate Ca(2+) influx in podocytes, and have been implicated in glomerular disease. We observed that AII increased cationic currents in rat podocytes in an isolated glomerulus preparation in which podocytes are still attached to the underlying capillary. This effect was completely blocked by SKF-96365, by micromolar La(3+) , and by siRNA knockdown of TRPC6, indicating that TRPC6 is the primary source of Ca(2+) influx mobilized by endogenously expressed angiotensin II receptors in these cells. These responses were also blocked by the AT1R antagonist losartan, the phospholipase C inhibitor D-609, and by inhibition of G protein signaling. The pan-protein kinase C inhibitor chelerythrine had no effect. Importantly, pretreating podocytes with the ROS quencher manganese (III) tetrakis (4-benzoic acid) porphyrin chloride (MnTBAP) eliminated AII activation of TRPC6. Significant reductions of AII effects on podocyte TRPC6 were also observed after pretreatment with NADPH oxidase inhibitors apocynin or diphenylene iodonium (DPI). These data suggest that ROS production permits activation of TRPC6 channels by G protein and PLC-dependent cascades initiated by AII acting on AT1Rs in podocytes. This pathway also provides a basis whereby two forms of cellular stress-oxidative stress and Ca(2+) overload-converge on common pathways relevant to disease.
Collapse
Affiliation(s)
- Marc Anderson
- Department of Biology and Biochemistry, University of Houston, Houston, Texas
| | | | | | | |
Collapse
|
20
|
|
21
|
Nistala R, Whaley-Connell A. Resistance to insulin and kidney disease in the cardiorenal metabolic syndrome; role for angiotensin II. Mol Cell Endocrinol 2013; 378:53-8. [PMID: 23416840 PMCID: PMC3711952 DOI: 10.1016/j.mce.2013.02.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Revised: 01/03/2013] [Accepted: 02/06/2013] [Indexed: 12/14/2022]
Abstract
The presence of insulin resistance is increasingly recognized as an important contributor to early stage kidney disease independent of the contribution of diabetes. Important in this relationship is the strong correlation between hyperinsulinemia and low levels of albuminuria (e.g. microalbuminuria). Recent work highlight mechanisms for glomerular/tubulointerstitial injury with excess insulin and emerging evidence identifies a unique role for insulin metabolic signaling and altered handling of salt reabsorption at the level of the proximal tubule. Evidence is also emerging for the role of insulin signaling in the glomerulus both epithelial and endothelial. Central to the mechanism of injury is inappropriate activation of the RAAS.
Collapse
Affiliation(s)
- Ravi Nistala
- University of Missouri School of Medicine, Diabetes and Cardiovascular Center, Departments of Internal Medicine, Divisions of Nephrology and Hypertension, United States; Dialysis Clinics Inc., Lemone Industrial Blvd., Columbia MO, United States.
| | | |
Collapse
|
22
|
Schießl IM, Castrop H. Angiotensin II AT2 receptor activation attenuates AT1 receptor-induced increases in the glomerular filtration of albumin: a multiphoton microscopy study. Am J Physiol Renal Physiol 2013; 305:F1189-200. [PMID: 23946289 DOI: 10.1152/ajprenal.00377.2013] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In this study, we assessed the acute effects of angiotensin II on the albumin glomerular sieving coefficient (GSC) using intravital microscopy. The experiments were performed on Munich Wistar Froemter (MWF) rats. Alexa-Fluor-594 albumin was injected intravenously, and the fluorescence intensity in the glomerular capillaries and Bowman's space was determined to calculate the albumin GSC. The GSC was measured before and during the constant infusion of angiotensin II (10 ng·min(-1)·kg(-1) body wt). Baseline mean arterial pressure (MAP) was 99 ± 5 mmHg and stabilized at 137 ± 5 mmHg during angiotensin II infusion. The baseline GSC averaged 0.00044 ± 4.8 × 10(-5) and increased by 286 ± 44% after angiotensin II infusion (P < 0.0001). The proximal tubular Alexa-Fluor-594 albumin uptake was enhanced during angiotensin II infusion (518% of the baseline value during angiotensin II vs. 218% in controls; P < 0.0001). No change in GSC was observed when the AT1 antagonist losartan was injected before the start of angiotensin II infusion. The AT2 antagonist PD123319 increased the baseline GSC from 0.00052 ± 3.6 × 10(-5) to 0.00074 ± 8.2 × 10(-5) (P = 0.02) without altering the MAP. During angiotensin II infusion with losartan, PD123319 increased the albumin GSC from 0.00037 ± 5.8 × 10(-5) to 0.00115 ± 0.00015 (P = 0.001). When the renal perfusion pressure was mechanically controlled, the GSC increased from 0.0007 ± 0.00019 to 0.0025 ± 0.00063 during angiotensin II infusion (P = 0.047), similar to what was observed when the renal perfusion pressure was allowed to increase. In summary, AT1 activation acutely increases the albumin GSC. This effect appears to be largely independent of changes in the renal perfusion pressure. The AT2 receptor partially attenuates the proteinuric effects of the AT1 receptor.
Collapse
Affiliation(s)
- Ina Maria Schießl
- Institute of Physiology, Univ. of Regensburg, Universitätsstr. 31, 93040 Regensburg, Germany.
| | | |
Collapse
|
23
|
Abstract
Ca(2+)-mediated remodeling of the actin cytoskeleton is a dynamic process that regulates cell motility through the modulation of rho guanosine triphosphatase (GTPase) signaling. Kidney podocytes are unique, pericyte-like cells with a complex cellular organization consisting of a cell body, major processes, and foot processes (FPs). The FPs form a characteristic interdigitating pattern with FPs of neighboring podocytes, leaving in between filtration slits that are covered by the slit diaphragm (SD). The actin-based FP and the SD form the final barrier to proteinuria. Mutations affecting several podocyte proteins cause disruption of the filtration barrier and rearrangement of the highly dynamic podocyte actin cytoskeleton. Proteins regulating the plasticity of the podocyte actin cytoskeleton are therefore of critical importance for sustained kidney barrier function. Dynamic regulation of the actin-based contractile apparatus in podocyte FPs is essential for sustained kidney filter function. Thus, the podocyte represents an excellent model system to study calcium signaling and actin dynamics in a physiologic context. Here, we discuss the regulation of podocyte actin dynamics by angiotensin or bradykinin-mediated calcium influx and downstream Rho GTPase signaling pathways and how these pathways are operative in other cells including fibroblasts and cancer cells.
Collapse
Affiliation(s)
- Anna Greka
- Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, 149 13th St, Charlestown, MA 02129, USA.
| | | |
Collapse
|
24
|
Wennmann DO, Hsu HH, Pavenstädt H. The renin-angiotensin-aldosterone system in podocytes. Semin Nephrol 2013; 32:377-84. [PMID: 22958492 DOI: 10.1016/j.semnephrol.2012.06.009] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The renin-angiotensin-aldosterone system (RAAS) plays a critical role in kidney function and its inhibition reduces proteinuria and preserves kidney function in patients with chronic kidney disease. Recent studies have shown that podocytes generate many components of the RAAS and they express receptors of RAAS, including angiotensin II, mineralocorticoid, and prorenin receptors. Crucial functions of podocytes, such as contraction, apoptosis, autophagocytosis, and cytoskeletal organization, have been shown to be regulated by the angiotensin II type 1 receptors. An activation of the glomerular RAAS and protection from podocyte injury by RAAS inhibitors have been shown in many glomerular diseases. Exploring the interaction between the local RAAS and the signaling involved in RAAS activation in podocytes will lead to new therapeutic strategies of podocyte protection.
Collapse
Affiliation(s)
- Dirk Oliver Wennmann
- Department of Internal Medicine D, University Hospital Münster, Münster, Germany
| | | | | |
Collapse
|
25
|
Ilatovskaya DV, Staruschenko A. Single-channel analysis of TRPC channels in the podocytes of freshly isolated Glomeruli. Methods Mol Biol 2013; 998:355-69. [PMID: 23529444 PMCID: PMC4181531 DOI: 10.1007/978-1-62703-351-0_28] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
One of the most important functions of the kidney is the filtration of the blood that takes place in the glomeruli. Glomerular epithelial cells (podocytes) have several functions, including regulation of the filtration process and glomerular basement membrane turnover. Dysfunction of podocytes is a major cause of glomerular kidney diseases. Gain-of-function mutations in the TRPC6 channel underlie a subset of familial forms of focal segmental glomerulosclerosis (FSGS). While growing evidence supports an important role of TRPC channels in podocytes, the regulation of these channels has yet to be investigated in freshly isolated glomeruli. Native settings in glomeruli provide, by all means, the most appropriate as well as one of the most challenging environments to study ion channel regulation. Thus, it is important to develop new methods that would better reflect the native settings of the podocytes. To address this question, we have established an experimental approach that allows studying podocytes in the freshly isolated decapsulated intact glomeruli. Here we describe the preparation of the rat glomeruli for patch-clamping, focusing on special conditions required for single-channel analysis of TRPC channels. Several tricks useful for cell-attached patch-clamping of the glomerular podocytes and solutions appropriate for registration of the TRPC channels are also provided.
Collapse
|
26
|
Shimizu A, Zhong J, Miyazaki Y, Hosoya T, Ichikawa I, Matsusaka T. ARB protects podocytes from HIV-1 nephropathy independently of podocyte AT1. Nephrol Dial Transplant 2012; 27:3169-75. [PMID: 22422866 DOI: 10.1093/ndt/gfs033] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Angiotensin I-converting enzyme inhibitors and angiotensin receptor blockers protect podocytes more effectively than other anti-hypertensive drugs. Transgenic rats overexpressing angiotensin II Type 1 (AT1) receptor selectively in podocytes have been shown to develop glomerulosclerosis. The prevailing hypothesis is that angiotensin II has a capacity of directly acting on the AT1 receptor of podocytes to induce injury. We therefore investigated the mechanism of reno-protective effect of AT1 receptor in a mouse model of HIV-1 nephropathy. METHODS We generated transgenic mice carrying the HIV-1 gene (control/HIV-1) or both HIV-1 gene and podocyte-selectively nullified AT1 gene (AT1KO/HIV-1). In these mice, we measured urinary protein or albumin excretion and performed histological analysis. RESULTS At 8 months of age, AT1KO/HIV-1 (n = 13) and control/HIV-1 (n = 15) mice were statistically indistinguishable with respect to urinary albumin/creatinine ratio (median 2.5 versus 9.1 mg/mg), glomerulosclerosis (median 0.63 versus 0.45 on 0-4 scale) and downregulation of nephrin (median 6.90 versus 7.02 on 0-8 scale). In contrast to the observed lack of effect of podocyte-specific AT1KO, systemic AT1 inhibition with AT1 blocker (ARB) significantly attenuated proteinuria and glomerulosclerosis in HIV-1 mice. CONCLUSION These results indicate that the protective effect of ARB is mediated through its receptors on cells other than podocytes, such as efferent arteriolar smooth muscle cells.
Collapse
Affiliation(s)
- Akihiro Shimizu
- Department of Internal Medicine, Tokai University School of Medicine, Isehara, Kanagawa, Japan.
| | | | | | | | | | | |
Collapse
|
27
|
Camici M, Galetta F, Abraham N, Carpi A. Obesity-related glomerulopathy and podocyte injury: a mini review. Front Biosci (Elite Ed) 2012; 4:1058-1070. [PMID: 22201936 PMCID: PMC5560488 DOI: 10.2741/e441] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Obesity-related glomerulopathy (ORG) is morphologically defined as focal segmental glomerulosclerosis and glomerulomegaly. Podocyte hypertrophy and reduced density are related to proteinuria which in a portion of patients is in the nephrotic range and evolvs towards renal failure. This article reviews the pathogenetic mechanisms of podocyte injury or dysfunction and lists new possible antiproteinuric strategies based on pharmaceutical targeting of the reported pathogenetic mechanisms. The pathogenetic mechnisms discussed include: renin angiotensin system, plasminogen activation inhibitor-1 (PAI-1), lipid metabolism, adiponectin, macrophages and proinflammatory cytokines, oxidative stress. The proposed antiproteinuric strategies include: AT2 receptor blockers; adipokine complement C19 TNF-related protein-1 blocker; selective PAI-1 inhibitor; farnesoid x receptor activation; increase of circulating adiponectin; selective antiinflammatory drugs; more potent antioxidants (Heme oxigenase, NOX4 inhibitors). However, because ORG is a rare disease, the need for a long term pharmaceutical approach in obese proteinuric patients should be carefully evaluated and limited to the cases with progressive loss of renal function.
Collapse
Affiliation(s)
| | - Fabio Galetta
- Department of Internal Medicine, University of Pisa, Italy
| | - Nader Abraham
- Department of Physiology and Pharmacology, University of Toledo, USA
| | - Angelo Carpi
- Department of Reproduction and Ageing, University of Pisa, Italy
| |
Collapse
|
28
|
Camici M, Galetta F, Abraham N, Carpi A. Obesity-related glomerulopathy and podocyte injury: a mini review. Front Biosci (Elite Ed) 2012. [PMID: 22201936 DOI: 10.2741/441] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Obesity-related glomerulopathy (ORG) is morphologically defined as focal segmental glomerulosclerosis and glomerulomegaly. Podocyte hypertrophy and reduced density are related to proteinuria which in a portion of patients is in the nephrotic range and evolvs towards renal failure. This article reviews the pathogenetic mechanisms of podocyte injury or dysfunction and lists new possible antiproteinuric strategies based on pharmaceutical targeting of the reported pathogenetic mechanisms. The pathogenetic mechnisms discussed include: renin angiotensin system, plasminogen activation inhibitor-1 (PAI-1), lipid metabolism, adiponectin, macrophages and proinflammatory cytokines, oxidative stress. The proposed antiproteinuric strategies include: AT2 receptor blockers; adipokine complement C19 TNF-related protein-1 blocker; selective PAI-1 inhibitor; farnesoid x receptor activation; increase of circulating adiponectin; selective antiinflammatory drugs; more potent antioxidants (Heme oxigenase, NOX4 inhibitors). However, because ORG is a rare disease, the need for a long term pharmaceutical approach in obese proteinuric patients should be carefully evaluated and limited to the cases with progressive loss of renal function.
Collapse
|
29
|
Abstract
As an integral member of the filtration barrier in the kidney glomerulus, the podocyte is in a unique geographical position: It is exposed to chemical signals from the urinary space (Bowman's capsule), it receives and transmits chemical and mechanical signals to/from the glomerular basement membrane upon which it elaborates, and it receives chemical and mechanical signals from the vascular space with which it also communicates. As with every cell, the ability of the podocyte to receive signals from the surrounding environment and to translate them to the intracellular milieu is dependent largely on molecules residing on the cell membrane. These molecules are the first-line soldiers in the ongoing battle to sense the environment, to respond to friendly signals, and to defend against injurious foes. In this review, we take a membrane biologist's view of the podocyte, examining the many membrane receptors, channels, and other signaling molecules that have been implicated in podocyte biology. Although we attempt to be comprehensive, our goal is not to capture every membrane-mediated pathway but rather to emphasize that this approach may be fruitful in understanding the podocyte and its unique properties.
Collapse
Affiliation(s)
- Anna Greka
- Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
| | | |
Collapse
|
30
|
Greka A, Mundel P. Balancing calcium signals through TRPC5 and TRPC6 in podocytes. J Am Soc Nephrol 2011; 22:1969-80. [PMID: 21980113 DOI: 10.1681/asn.2011040370] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Calcium (Ca(2+)) ions are important mediators of cellular homeostasis owing to their ability to elicit a dynamic, transient, and tightly regulated range of biochemical responses. More than a decade ago, a nonselective, Ca(2+)-permeable, cationic conductance was identified in podocytes downstream of angiotensin II (Ang II) signaling, but its molecular structure remained elusive. Six years ago, transient receptor potential canonical 6 (TRPC6) mutations were found in families with hereditary FSGS, and TRPC5 and TRPC6 channels are now known as the Ca(2+) influx pathways for this previously described, nonselective, cationic current in podocytes. Ang II activation engages this Ca(2+) influx to modulate the actin cytoskeleton in podocytes. These discoveries dovetail with previously described regulation of actin dynamics by the Ca(2+)-activated phosphatase, calcineurin, and the emergence of Rho GTPases as critical regulators of podocyte function in health and disease. Understanding the interconnected signaling regulated by Ca(2+) currents offers potential new therapeutic targets and highlights the notion that synergistic therapies targeting multiple levels of biochemistry may be useful in treating proteinuric kidney disease.
Collapse
Affiliation(s)
- Anna Greka
- Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA.
| | | |
Collapse
|
31
|
Angiotensin II contributes to podocyte injury by increasing TRPC6 expression via an NFAT-mediated positive feedback signaling pathway. THE AMERICAN JOURNAL OF PATHOLOGY 2011; 179:1719-32. [PMID: 21839714 DOI: 10.1016/j.ajpath.2011.06.033] [Citation(s) in RCA: 168] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Revised: 05/09/2011] [Accepted: 06/10/2011] [Indexed: 01/31/2023]
Abstract
The transient receptor potential channel C6 (TRPC6) is a slit diaphragm-associated protein in podocytes involved in regulating glomerular filter function. Gain-of-function mutations in TRPC6 cause hereditary focal segmental glomerulosclerosis (FSGS), and several human acquired proteinuric diseases show increased glomerular TRPC6 expression. Angiotensin II (AngII) is a key contributor to glomerular disease and may regulate TRPC6 expression in nonrenal cells. We demonstrate that AngII regulates TRPC6 mRNA and protein levels in cultured podocytes and that AngII infusion enhances glomerular TRPC6 expression in vivo. In animal models for human FSGS (doxorubicin nephropathy) and increased renin-angiotensin system activity (Ren2 transgenic rats), glomerular TRPC6 expression was increased in an AngII-dependent manner. TRPC6 expression correlated with glomerular damage markers and glomerulosclerosis. We show that the regulation of TRPC6 expression by AngII and doxorubicin requires TRPC6-mediated Ca(2+) influx and the activation of the Ca(2+)-dependent protein phosphatase calcineurin and its substrate nuclear factor of activated T cells (NFAT). Accordingly, calcineurin inhibition by cyclosporine decreased TRPC6 expression and reduced proteinuria in doxorubicin nephropathy, whereas podocyte-specific inducible expression of a constitutively active NFAT mutant increased TRPC6 expression and induced severe proteinuria. Our findings demonstrate that the deleterious effects of AngII on podocytes and its pathogenic role in glomerular disease involve enhanced TRPC6 expression via a calcineurin/NFAT positive feedback signaling pathway.
Collapse
|
32
|
Downregulation of the antioxidant protein peroxiredoxin 2 contributes to angiotensin II-mediated podocyte apoptosis. Kidney Int 2011; 80:959-969. [PMID: 21814176 PMCID: PMC3257043 DOI: 10.1038/ki.2011.250] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Podocytes have a significant role in establishing selective permeability of the glomerular filtration barrier. Sustained renin–angiotensin–aldosterone system activation is crucial to the pathogenesis of podocyte injury, but the mechanisms by which angiotensin II modulates podocyte survival due to physiological or injurious stimuli remain unclear. Here, we used proteomic analysis to find new mediators of angiotensin II–induced podocyte injury. Antioxidant protein peroxiredoxin 2 expression was decreased in cultured podocytes stimulated with angiotensin II. Peroxiredoxin 2 was found to be expressed in podocytes in vivo, and its expression was decreased in the glomeruli of rats transgenic for angiotensin II type 1 receptors in a podocyte-specific manner, or in rats infused with angiotensin II. Downregulation of peroxiredoxin 2 in podocytes resulted in increased reactive oxygen species release, protein overoxidation, and inhibition of the Akt pathway. Both treatment with angiotensin II and downregulation of peroxiredoxin 2 expression led to apoptosis of podocytes. Thus, peroxiredoxin 2 is an important modulator of angiotensin II–induced podocyte injury.
Collapse
|
33
|
Diez-Sampedro A, Lenz O, Fornoni A. Podocytopathy in diabetes: a metabolic and endocrine disorder. Am J Kidney Dis 2011; 58:637-46. [PMID: 21719174 DOI: 10.1053/j.ajkd.2011.03.035] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Accepted: 03/04/2011] [Indexed: 12/17/2022]
Abstract
Diabetic nephropathy (DN) represents a major public health cost. Tight glycemic and blood pressure control can dramatically slow, but not stop, the progression of the disease, and a large number of patients progress toward end-stage renal disease despite currently available interventions. An early and key event in the development of DN is loss of podocyte function (or glomerular visceral epithelial cells) from the kidney glomerulus, where they contribute to the integrity of the glomerular filtration barrier. Recent evidence suggests that podocytes can be the direct target of circulating hormones, lipids, and adipokines that are affected in diabetes. We review the clinical and experimental evidence implicating novel endocrine and metabolic pathways in the pathogenesis of podocyte dysfunction and the development of DN.
Collapse
Affiliation(s)
- Ana Diez-Sampedro
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, FL, USA
| | | | | |
Collapse
|
34
|
NSAIDs acutely inhibit TRPC channels in freshly isolated rat glomeruli. Biochem Biophys Res Commun 2011; 408:242-7. [PMID: 21473850 DOI: 10.1016/j.bbrc.2011.04.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Accepted: 04/01/2011] [Indexed: 11/20/2022]
Abstract
Using a novel approach for analysis of TRPC channel activity, we report here that NSAIDs are involved into regulation of TRPC channels in the podocytes of the freshly isolated decapsulated glomeruli. Fluorescence and electron microscopy techniques confirmed the integrity of podocytes in the glomeruli. Western blotting showed that TRPC1, 3 and 6 are highly expressed in the glomeruli. Single-channel patch clamp analysis revealed cation currents with distinct TRPC properties. This is the first report describing single TRPC-like currents in glomerular podocytes. Furthermore, our data provide a novel mechanism of NSAIDs regulation of TRPC channels, which might be implicated in maintaining the glomerular filtration barrier.
Collapse
|
35
|
Campbell KN, Raij L, Mundel P. Role of angiotensin II in the development of nephropathy and podocytopathy of diabetes. Curr Diabetes Rev 2011; 7:3-7. [PMID: 21067505 PMCID: PMC3690294 DOI: 10.2174/157339911794273973] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 09/10/2010] [Indexed: 01/03/2023]
Abstract
Diabetic kidney disease is the leading cause of end-stage renal disease worldwide. Podocytes are highly differentiated, pericyte-like cells that are essential for normal function of the kidney filter. Loss of podocytes is a hallmark of progressive kidney diseases including diabetic nephropathy. Podocytes are a direct target for angiotensin II - mediated injury by altered expression and distribution of podocyte proteins. Additionally, angiotensin II promotes podocyte injury indirectly by increasing calcium influx and production of reactive oxygen species. Notwithstanding the convincing rationale for angiotensin II blockade as a treatment modality, the incidence of diabetes-related end stage renal disease has increased steadily despite widespread use of angiotensin converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs). Recently published clinical trials have rekindled a debate on the safety and efficacy of dual blockade of the renin-angiotensin system (RAS). This review summarizes the rationale for blockade of angiotensin II as a therapeutic target in treating diabetic kidney disease, including the critical role played by podocytes. Recent relevant clinical trials on the role of RAS blockade in the treatment of diabetic kidney disease are discussed.
Collapse
Affiliation(s)
- Kirk N Campbell
- Department of Medicine, Leonard Miller School of Medicine, University of Miami, 1580 NW 10th Avenue, Miami, FL 33136, USA.
| | | | | |
Collapse
|
36
|
Matsusaka T, Asano T, Niimura F, Kinomura M, Shimizu A, Shintani A, Pastan I, Fogo AB, Ichikawa I. Angiotensin receptor blocker protection against podocyte-induced sclerosis is podocyte angiotensin II type 1 receptor-independent. Hypertension 2010; 55:967-73. [PMID: 20142565 DOI: 10.1161/hypertensionaha.109.141994] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
In the present study, we tested the hypothesis that the renoprotective effect of an angiotensin receptor blocker depends on the angiotensin II type 1 (AT(1)) receptor on podocytes. For this purpose, we generated podocyte-specific knockout mice for the AT(1) gene (Agtr1a) and crossed with NEP25, in which selective podocyte injury can be induced by immunotoxin, anti-Tac(Fv)-PE38. Four weeks after the addition of anti-Tac(Fv)-PE38, urinary albumin:creatinine ratio was not attenuated in Agtr1a knockout/NEP25 mice (n=18) compared with that in control NEP25 mice (n=13; 8.08+/-2.41 in knockout versus 4.84+/-0.73 in control). Both strains of mice showed similar degrees of sclerosis (0.66+/-0.17 versus 0.82+/-0.27 on a 0 to 4 scale) and downregulation of nephrin (5.78+/-0.45 versus 5.65+/-0.58 on a 0 to 8 scale). In contrast, AT(1) antagonist or an angiotensin I-converting enzyme inhibitor, but not hydralazine, remarkably attenuated proteinuria and sclerosis in NEP25 mice. Moreover, continuous angiotensin II infusion induced microalbuminuria similarly in both Agtr1a knockout and wild-type mice. Thus, angiotensin inhibition can protect podocytes and prevent the development of glomerulosclerosis independent of podocyte AT(1). Possible mechanisms include inhibitory effects on AT(1) of other cells or through mechanisms independent of AT(1). Our study further demonstrates that measures that directly affect only nonpodocyte cells can have beneficial effects even when sclerosis is triggered by podocyte-specific injury.
Collapse
Affiliation(s)
- Taiji Matsusaka
- Departments of Pediatrics, Vanderbilt University Medical Center, Nashville, Tenn, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Ghayur MN, Janssen LJ. Real-time Imaging of Ca-handling in Intact Renal Glomeruli Using Confocal Microscopy. MEDICAL HYPOTHESES AND RESEARCH : MHR 2009; 5:47-56. [PMID: 22287941 PMCID: PMC3266942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Glomeruli are filtering units in the kidneys. Being multicellular and complex in structure, many aspects of glomerular function are yet to be elucidated. Most studies use glomerular cells in culture, which may exhibit altered physiology compared to native cells. Confocal microscopy has opened new avenues in exploring in situ glomerular function and physiology. In this report, we propose experimenting with glomerular cells in renal cortical slices and isolated intact glomeruli for Ca(2+)-handling studies. Cortical slices (100 μm thick) were obtained from mice while intact glomeruli were isolated from rats using the sieving method. These were loaded with fluo-4 and then placed in a confocal microscope. Fluo-4 was excited using a 488 nm photodiode laser and images were collected at 1 frame/sec. Changes in average fluorescence intensity (AFI) were interpreted as changes in [Ca(2+)](i). AFI increased to 37.1 ± 6.7% and 84.3 ± 20.9% with Ang II (0.01 and 0.1 μM respectively). Norepinephrine (10 μM), arginine vasopressin (0.1 μM) and K(+) (30 mM) also elevated AFI by 26.5 ± 6.8%, 22.3 ± 1.0% and 39.8 ± 10.3% respectively in the glomerular cells. Likewise in isolated glomeruli, Ang II (0.1-10 μM), K(+) (30-90 mM) and endothelin-1 (0.01-1 μM), all showed elevation in [Ca(2+)](i). These results give an impetus for future studies examining Ca(2+)-handling by confocal microscopy in glomerular cells using renal cortical slices and isolated intact glomeruli. The results support the utility of this system for study of glomerular physiology and pharmacology.
Collapse
Affiliation(s)
- Muhammad Nabeel Ghayur
- Department of Medicine, McMaster University, St. Joseph's Hospital, Hamilton, Ontario, Canada
| | | |
Collapse
|
38
|
Hsu HH, Hoffmann S, Endlich N, Velic A, Schwab A, Weide T, Schlatter E, Pavenstädt H. Mechanisms of angiotensin II signaling on cytoskeleton of podocytes. J Mol Med (Berl) 2008; 86:1379-94. [PMID: 18773185 DOI: 10.1007/s00109-008-0399-y] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 07/12/2008] [Accepted: 08/01/2008] [Indexed: 01/16/2023]
Abstract
Podocytes are significant in establishing the glomerular filtration barrier. Sustained rennin-angiotensin system (RAS) activation is crucial in the pathogenesis of podocyte injury and causes proteinuria. This study demonstrates that angiotensin II (Ang II) caused a reactive oxygen species (ROS)-dependent rearrangement of cortical F-actin and a migratory phenotype switch in cultured mouse podocytes with stable Ang II type 1 receptor (AT1R) expression. Activated small GTPase Rac-1 and phosphorylated ezrin/radixin/moesin (ERM) proteins provoked Ang II-induced F-actin cytoskeletal remodeling. This work also shows increased expression of Rac-1 and phosphorylated ERM proteins in cultured podocytes, and in glomeruli of podocyte-specific AT1R transgenic rats (Neph-hAT1 TGRs). The free radical scavenger DMTU eliminated Ang II-induced cell migration, ERM protein phosphorylation and cortical F-actin remodeling, indicating that ROS mediates the influence of Rac-1 on podocyte AT1R signaling. Heparin, a potent G-coupled protein kinase 2 inhibitor, was found to abolish ERM protein phosphorylation and cortical F-actin ring formation in Ang II-treated podocytes, indicating that phosphorylated ERM proteins are the cytoskeletal effector in AT1R signaling. Moreover, Ang II stimulation triggered down-regulation of alpha actinin-4 and reduced focal adhesion expression in podocytes. Signaling inhibitor assay of Ang II-treated podocytes reveals that Rac-1, RhoA, and F-actin reorganization were involved in expressional regulation of alpha actinin-4 in AT1R signaling. With persistent RAS activation, the Ang II-induced phenotype shifts from being dynamically stable to adaptively migratory, which may eventually exhaust podocytes with a high actin cytoskeletal turnover, causing podocyte depletion and focal segmental glomerulosclerosis.
Collapse
Affiliation(s)
- Hsiang-Hao Hsu
- Department of Medicine D, Division of General Internal Medicine and Nephrology, University Hospital Muenster, Albert-Schweitzer-Str. 33, 48149 Muenster, Germany
| | | | | | | | | | | | | | | |
Collapse
|
39
|
Saleem MA, Zavadil J, Bailly M, McGee K, Witherden IR, Pavenstadt H, Hsu H, Sanday J, Satchell SC, Lennon R, Ni L, Bottinger EP, Mundel P, Mathieson PW. The molecular and functional phenotype of glomerular podocytes reveals key features of contractile smooth muscle cells. Am J Physiol Renal Physiol 2008; 295:F959-70. [PMID: 18684887 PMCID: PMC2576149 DOI: 10.1152/ajprenal.00559.2007] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The glomerular podocyte is a highly specialized cell, with the ability to ultrafilter blood and support glomerular capillary pressures. However, little is known about either the genetic programs leading to this functionality or the final phenotype. We approached this question utilizing a human conditionally immortalized cell line, which differentiates from a proliferating epithelial phenotype to a differentiated form. We profiled gene expression during several time points during differentiation and grouped the regulated genes into major functional categories. A novel category of genes that was upregulated during differentiation was of smooth muscle-related molecules. We further examined the smooth muscle phenotype and showed that podocytes consistently express the differentiated smooth muscle markers smoothelin and calponin and the specific transcription factor myocardin, both in vitro and in vivo. The contractile contribution of the podocyte to the glomerular capillary is controversial. We demonstrated using two novel techniques that podocytes contract vigorously in vitro when differentiated and in real time were able to demonstrate that angiotensin II treatment decreases monolayer resistance, morphologically correlating with enhanced contractility. We conclude that the mature podocyte in vitro possesses functional apparatus of contractile smooth muscle cells, with potential implications for its in vivo ability to regulate glomerular dynamic and permeability characteristics.
Collapse
Affiliation(s)
- Moin A Saleem
- Academic and Children's Renal Unit, University of Bristol, Lifeline Bldg., Southmead Hospital, Bristol, BS10 5NB, United Kingdom.
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Stirban A, Rösen P, Tschoepe D. Complications of type 1 diabetes: new molecular findings. ACTA ACUST UNITED AC 2008; 75:328-51. [DOI: 10.1002/msj.20057] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
|
41
|
Studying channel and receptor physiology in podocytes. Kidney Int 2008; 73:364. [PMID: 18195704 DOI: 10.1038/sj.ki.5002669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
42
|
Whaley-Connell A, Habibi J, Nistala R, Cooper SA, Karuparthi PR, Hayden MR, Rehmer N, DeMarco VG, Andresen BT, Wei Y, Ferrario C, Sowers JR. Attenuation of NADPH oxidase activation and glomerular filtration barrier remodeling with statin treatment. Hypertension 2008; 51:474-80. [PMID: 18172055 DOI: 10.1161/hypertensionaha.107.102467] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Activation of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase by angiotensin II is integral to the formation of oxidative stress in the vasculature and the kidney. 3-Hydroxy-3-methylglutaryl-coenzyme A reductase inhibition is associated with reductions of oxidative stress in the vasculature and kidney and associated decreases in albuminuria. Effects of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibition on oxidative stress in the kidney and filtration barrier integrity are poorly understood. To investigate, we used transgenic TG(mRen2)27 (Ren2) rats, which harbor the mouse renin transgene and renin-angiotensin system activation, and an immortalized murine podocyte cell line. We treated young, male Ren2 and Sprague-Dawley rats with rosuvastatin (20 mg/kg IP) or placebo for 21 days. Compared with controls, we observed increases in systolic blood pressure, albuminuria, renal NADPH oxidase activity, and 3-nitrotryosine staining, with reductions in the rosuvastatin-treated Ren2. Structural changes on light and transmission electron microscopy, consistent with periarteriolar fibrosis and podocyte foot-process effacement, were attenuated with statin treatment. Nephrin expression was diminished in the Ren2 kidney and trended to normalize with statin treatment. Angiotensin II-dependent increases in podocyte NADPH oxidase activity and subunit expression (NOX2, NOX4, Rac, and p22(phox)) and reactive oxygen species generation were decreased after in vitro statin treatment. These data support a role for increased NADPH oxidase activity and subunit expression with resultant reactive oxygen species formation in the kidney and podocyte. Furthermore, statin attenuation of NADPH oxidase activation and reactive oxygen species formation in the kidney/podocyte seems to play roles in the abrogation of oxidative stress-induced filtration barrier injury and consequent albuminuria.
Collapse
Affiliation(s)
- Adam Whaley-Connell
- University of Missouri-Columbia School of Medicine, Department of Internal Medicine, Division of Nephrology, MA436, DC043.0, One Hospital Dr, Columbia, MO 65212, USA.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
43
|
GHAYUR MUHAMMADN, KREPINSKY JOANC, JANSSEN LUKEJ. CONTRACTILITY OF THE RENAL GLOMERULUS AND MESANGIAL CELLS: LINGERING DOUBTS AND STRATEGIES FOR THE FUTURE. MEDICAL HYPOTHESES AND RESEARCH : MHR 2008; 4:1-9. [PMID: 22287940 PMCID: PMC3266944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Kidneys can be divided into four components: glomeruli, tubules, interstitium and blood vessels. The renal glomerulus consists of a network of capillaries covered with epithelial cells called podocytes. The entire glomerular tuft is structurally supported by mesangial cells which are contractile in nature and resemble vascular smooth muscle cells. Mesangial cells are secretory, producing growth factors and matrix proteins which have a role in both normal glomerular development and in pathologic states. They have also been shown to take the role of macrophages. The importance of mesangial cell contraction to glomerular physiology remains debated. It is postulated that mesangial cell contraction can attenuate the glomerular filtration rate by decreasing the renal ultrafiltration coefficient through a decrease in capillary surface area and capillary permeability. The physiology of mesangial cell contraction has been studied primarily utilizing cultured cells. The physiological status of receptors and ion channels may be doubtful, however, given the phenotypic changes cells are known to acquire in culture conditions. The contractility of renal glomeruli has been less well studied. In this report, we review the available data regarding the contractility of mesangial cell and of renal glomeruli. Moreover, we suggest newer techniques that can be used with whole glomeruli, thereby improving upon the data collected using previous techniques and cultured cells.
Collapse
Affiliation(s)
| | | | - LUKE J. JANSSEN
- Correspondence: Luke J. Janssen, PhD, Department of Medicine, McMaster University, St. Joseph’s Hospital, Room L-314, 50 Charlton Avenue East, Hamilton, Ontario L8N 4A6, Canada, Tel: (905) 522 1155 (Ext. 35912), Fax: (905) 540 6510,
| |
Collapse
|
44
|
Kwoh C, Shannon MB, Miner JH, Shaw A. Pathogenesis of nonimmune glomerulopathies. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2007; 1:349-74. [PMID: 18039119 DOI: 10.1146/annurev.pathol.1.110304.100119] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Nonimmune glomerulopathies are an area of significant research. This review discusses the development of focal segmental glomerulosclerosis, with particular attention to the role of the podocyte in the initiation of glomerulosclerosis and the contribution to glomerulosclerosis from capillary hypertension and soluble factors such as transforming growth factor beta, platelet-derived growth factor, vascular endothelial growth factor, and angiotensin. The effects of these factors on endothelial and mesangial cells are also discussed. In addition, we review our current understanding of the slit diaphragm (a specialized cell junction found in the kidney), slit diaphragm-associated proteins (including nephrin, podocin, alpha-actinin-4, CD2-associated protein, and transient receptor potential channel 6), and the role of these proteins in glomerular disease. We also discuss the most recent research on the pathogenesis of collapsing glomerulosclerosis, human immunodeficiency virus associated nephropathy, Denys-Drash, diabetic nephropathy, Alport syndrome, and other diseases related to the interaction between the podocyte and the glomerular basement membrane.
Collapse
Affiliation(s)
- Christopher Kwoh
- Renal Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63113, USA.
| | | | | | | |
Collapse
|
45
|
Reiser J, Mundel P. Dual effects of RAS blockade on blood pressure and podocyte function. Curr Hypertens Rep 2007; 9:403-8. [DOI: 10.1007/s11906-007-0074-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
|
46
|
Ideura H, Hiromura K, Hiramatsu N, Shigehara T, Takeuchi S, Tomioka M, Sakairi T, Yamashita S, Maeshima A, Kaneko Y, Kuroiwa T, Kopp JB, Nojima Y. Angiotensin II provokes podocyte injury in murine model of HIV-associated nephropathy. Am J Physiol Renal Physiol 2007; 293:F1214-21. [PMID: 17652372 DOI: 10.1152/ajprenal.00162.2007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Conditional transgenic mice that express one of the human immunodeficiency virus (HIV)-1 accessory genes, vpr, selectively in podocytes using a podocin promoter and a tetracycline-inducible system develop renal injuries similar to those of patients with HIV-associated nephropathy (HIVAN). We have shown that a heminephrectomy accelerates podocyte injury, which is alleviated by angiotensin II (ANG II) type 1 receptor blocker (ARB). The current study further explores the role of ANG II in the genesis of HIVAN in this murine model. With ANG II infusion, heavy proteinuria was observed at 1 wk after the initiation of doxycycline administration to induce vpr expression in podocytes. Severe morphological and phenotypical changes in the podocytes were observed at 2 wk, together with extensive glomerulosclerosis. Norepinephrine infusion, instead of ANG II, increased the systemic blood pressure to the same level as that achieved using ANG II. However, albuminuria and glomerular injury were modest in norepinephrine-infused mice. Treatment with an ARB, olmesartan, almost completely inhibited glomerular injury. In contrast, lowering the blood pressure with a vasodilator, hydralazine, partially decreased albuminuria but did not produce any histological changes. ANG II infusion alone without doxycycline resulted in a lower level of albuminuria and minimal histological changes. These data demonstrate that excessive ANG II accelerates vpr-induced podocyte injury in a mouse model of HIVAN.
Collapse
Affiliation(s)
- Hiroshi Ideura
- Department of Medicine and Clinical Science, Gunma University Graduste School of Medicine, Maebashi, Gunma, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
47
|
Hiramatsu N, Hiromura K, Shigehara T, Kuroiwa T, Ideura H, Sakurai N, Takeuchi S, Tomioka M, Ikeuchi H, Kaneko Y, Ueki K, Kopp JB, Nojima Y. Angiotensin II type 1 receptor blockade inhibits the development and progression of HIV-associated nephropathy in a mouse model. J Am Soc Nephrol 2007; 18:515-27. [PMID: 17229913 DOI: 10.1681/asn.2006030217] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
HIV-associated nephropathy (HIVAN) is characterized by a collapsed glomerular capillary tuft with hyperplasia and hypertrophy of podocytes. Recently generated were conditional transgenic mice (podocin/Vpr) that express one of the HIV-1 accessory genes, vpr, selectively in podocytes using podocin promoter and Tet-on system. These transgenic mice developed renal injury similar to HIVAN when treated with doxycycline for 8 to 12 wk. This study demonstrated that nephron reduction by heminephrectomy markedly enhanced phenotypic changes of podocytes and led to severe FSGS within 4 wk. Nephrotic-range proteinuria was observed already at 2 wk, together with dedifferentiation and dysregulation of podocytes, indicated by decreased expression of nephrin, synaptopodin, and Wilms' tumor 1 protein and increased expression of Ki-67. The acceleration of phenotypic changes of podocytes, proteinuria, and subsequent glomerulosclerosis by heminephrectomy was almost completely inhibited by angiotensin II type 1 receptor (AT1R) blocker olmesartan. In contrast, the renoprotective effect of the calcium channel antagonist azelnidipine was minimal, although it lowered systemic BP to the same level as olmesartan, demonstrating that the inhibitory effect of AT1R blocker was independent of systemic BP. Olmesartan also reduced proteinuria and prevented glomerulosclerosis even by the delayed treatment, which was initiated after the podocyte injury appeared. These data suggest that nephron reduction exaggerates podocyte injury and subsequent glomerulosclerosis, possibly through glomerular hypertension, in the mouse model of HIVAN. AT1R blockade could be beneficial in the treatment of HIVAN by ameliorating podocyte injury by avoiding the vicious cycle of nephron reduction and glomerular hypertension.
Collapse
Affiliation(s)
- Noriyuki Hiramatsu
- Department of Medicine and Clinical Science, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma 371-8511, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
48
|
Whaley-Connell AT, Chowdhury NA, Hayden MR, Stump CS, Habibi J, Wiedmeyer CE, Gallagher PE, Tallant EA, Cooper SA, Link CD, Ferrario C, Sowers JR. Oxidative stress and glomerular filtration barrier injury: role of the renin-angiotensin system in the Ren2 transgenic rat. Am J Physiol Renal Physiol 2006; 291:F1308-14. [PMID: 16788142 DOI: 10.1152/ajprenal.00167.2006] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
TG(mRen2)27 (Ren2) transgenic rats overexpress the mouse renin gene, manifest hypertension, and exhibit increased tissue ANG II levels and oxidative stress. Evidence indicates that elevated tissue ANG II contributes to oxidative stress, increases in glomerular macromolecular permeability, and consequent albuminuria. Furthermore, angiotensin type 1 receptor (AT1R) blockers reduce albuminuria and slow progression of renal disease. However, it is not known whether improvements in glomerular filtration barrier integrity and albuminuria during treatment are related to reductions in oxidative stress and/or kidney renin-angiotensin system (RAS) activity. To investigate the renal protective effects of AT1R blockade, we treated young (6-7 wk old) male Ren2 rats with valsartan (Ren2-V; 30 mg/kg) for 3 wk and measured urine albumin, kidney malondialdehyde (MDA), RAS component mRNAs, and NADPH oxidase subunits (gp91(phox) and Rac1) compared with age-matched untreated Ren2 and Sprague-Dawley (S-D) rats. Basement membrane thickness, slit pore diameter and number, and foot process base width were measured by transmission electron microscopy (TEM). Results indicate that AT1R blockade lowered systolic blood pressure (30%), albuminuria (91%), and kidney MDA (80%) in Ren2-V compared with untreated Ren2 rats. Increased slit pore number and diameter and reductions in basement membrane thickness and podocyte foot process base width were strongly associated with albuminuria and significantly improved following AT1R blockade. AT1R blockade was also associated with increased angiotensin-converting enzyme-2 and neprilysin expression, demonstrating a beneficial shift in balance of renal RAS. Thus reductions in blood pressure, albuminuria, and tissue oxidative stress with AT1R blockade were associated with improved indexes of glomerular filtration barrier integrity and renal RAS in Ren2 rats.
Collapse
Affiliation(s)
- Adam T Whaley-Connell
- Department of Internal Medicine, University of Missouri School of Medicine, 1 Hospital Dr., MA410 Medical Science Bldg., Columbia, MO 65212, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
49
|
Whaley-Connell A, Pavey BS, Afroze A, Bakris GL. Obesity and Insulin Resistance As Risk Factors for Chronic Kidney Disease. ACTA ACUST UNITED AC 2006; 1:209-14; quiz 215-6. [PMID: 17679819 DOI: 10.1111/j.1559-4564.2006.05631.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The cardiometabolic syndrome is a state of metabolic and vascular dysregulation. The cardiometabolic syndrome is clinically composed of a cluster of metabolic abnormalities including insulin resistance/hyperinsulinemia, central/visceral obesity, dyslipidemia, hypertension, microalbuminuria, fibrinolytic and inflammatory abnormalities, endothelial dysfunction, oxidative stress, and hypercoagulability, which collectively lead to an increased risk of cardiovascular and renal outcomes. The development of microalbuminuria is now accepted as a marker of systemic endothelial dysfunction and, if it progresses to macroalbuminuria (i.e., >200 mg/d albuminuria), then kidney disease is evident. Collectively, visceral obesity, insulin resistance/hyperinsulinemia, and other components of the cardiometabolic syndrome lead to an increased risk of microalbuminuria and progressive loss of renal function. Hence, aggressive management of risk factors for the metabolic syndrome, nonpharmacologic and pharmacologic, is essential to prevent or delay the progressive loss of renal function and chronic kidney disease.
Collapse
Affiliation(s)
- Adam Whaley-Connell
- Department of Internal Medicine, Division of Nephrology, University of Missouri School of Medicine, Columbia, MO, USA.
| | | | | | | |
Collapse
|
50
|
|