801
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Affiliation(s)
| | - Luis A Juncos
- Department of Medicine and Division of Nephrology, and Department of Physiology, University of Mississippi Medical Center, Jackson, Mississippi
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802
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Hao L, Pan MS, Zheng Y, Wang RF. Effect of Cordyceps sinensis and Tripterygium wilfordii polyglycosidium on podocytes in rats with diabetic nephropathy. Exp Ther Med 2014; 7:1465-1470. [PMID: 24926327 PMCID: PMC4043575 DOI: 10.3892/etm.2014.1670] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Accepted: 03/03/2014] [Indexed: 11/24/2022] Open
Abstract
The aim of the present study was to investigate the effects of Cordyceps sinensis (CS) and Tripterygium wilfordii polyglycosidium (TWP) on podocytes in rats with diabetic nephropathy (DN). DN rat models were established and divided randomly into normal control (group A), DN (group B), CS (group C), TWP (group D) and CS and TWP groups (group E). After 12 weeks, levels of 24-h urinary protein, blood urea nitrogen (BUN), serum creatinine (SCR), white blood cells, blood glucose (GLU), aspartate aminotransferase, alanine aminotransferase and kidney weight (KW)/body weight (BW) were determined. Renal pathological changes were evaluated using hematoxylin and eosin staining, whereas the structural changes in the podocytes were observed under a transmission electron microscope. The expression levels of nephrin and podocin were evaluated using immunofluorescence staining. Compared with group A, the SCR and BUN levels in group B were higher (P<0.05) and the GLU, KW/BW and the 24-h urine protein were markedly higher (P<0.01). Moreover, incidences of glomerular disorders, chronic tubulointerstitial damage and glomerular podocyte lesions in groups B, C, D and E were observed, compared with group A. The high cortical expression of nephrin and podocin protein decreased. Compared with group B, the KW/BW and 24-h urinary protein level in groups C, D and E were lower (P<0.01). The glomeruli, tubules and podocytes exhibited pathomorphological improvements and the nephrin and podocin protein expression levels were higher in the nephridial tissue. A decrease in KW/BW and the 24-h urinary protein level, as well as improvements in glomerular disorder, chronic tubulointerstitial damage and glomerular podocyte lesions, were observed in groups C, D and E. Therefore, the results demonstrated that CS and TWP exhibited a protective effect on the podocytes of rats with DN. Moreover, CS combined with TWP increased this protective effect.
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Affiliation(s)
- Li Hao
- Department of Nephrology, The Second Affiliated Hospital of Anhui Medical University, Hefei, Anhui 230601, P.R. China
| | - Meng-Shu Pan
- Department of Nephrology, The Second Affiliated Hospital of Anhui Medical University, Hefei, Anhui 230601, P.R. China
| | - Yun Zheng
- Department of Nephrology, The Second Affiliated Hospital of Anhui Medical University, Hefei, Anhui 230601, P.R. China
| | - Rui-Feng Wang
- Department of Nephrology, The Second Affiliated Hospital of Anhui Medical University, Hefei, Anhui 230601, P.R. China
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803
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Manson JJ, Mills K, Jury E, Mason L, D'Cruz DP, Ni L, Saleem M, Mathieson P, Isenberg D, Rahman A. Pathogenic autoantibodies from patients with lupus nephritis cause reduced tyrosine phosphorylation of podocyte proteins, including tubulin. Lupus Sci Med 2014; 1:e000013. [PMID: 25396061 PMCID: PMC4225730 DOI: 10.1136/lupus-2014-000013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Revised: 03/10/2014] [Accepted: 03/14/2014] [Indexed: 11/04/2022]
Abstract
INTRODUCTION The tertiary structure of normal podocytes prevents protein from leaking into urine. Patients with lupus nephritis (LN) develop proteinuria, and kidney biopsies from these patients display a number of podocyte abnormalities including retraction of podocyte processes. Autoantibodies have been shown to deposit in the kidneys of patients and mice with LN and are believed to play a key role in causing renal inflammation and dysfunction. The objective of this research was to study the effects of IgG antibodies from patients with LN on cultured human podocytes. METHODS We exposed a human podocyte cell line to heat-inactivated (HI) plasma and purified polyclonal IgG from the following groups of subjects; patients with LN, patients with lupus without nephritis, patients with rheumatoid arthritis and healthy controls. We measured expression and intracellular distribution of podocyte-specific proteins and global phosphorylation of tyrosine. We then used mass spectrometry to identify the major protein targets of this phosphorylation. RESULTS HI LN plasma did not alter expression or cellular distribution of podocyte-specific proteins but caused a significant reduction in podocyte protein tyrosine phosphorylation compared with plasma from healthy controls (p=0.0008). This result was replicated using purified IgG but was not seen with plasma from rheumatoid arthritis or non-renal lupus patients. The dominant tyrosine phosphorylated protein in podocytes was 55 kDa in size and was identified as tubulin. CONCLUSIONS Since tubulin is an important component of podocyte major processes, these results suggest that autoantibodies from LN patients may exert an important pathogenic effect by dephosphorylation of this protein in podocytes.
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Affiliation(s)
- Jessica J Manson
- Division of Medicine , Centre for Rheumatology Research, University College London, Rayne Institute , London , UK
| | - Kevin Mills
- Clinical and Molecular Genetics Unit , Institute for Child Health and Great Ormond Street Hospital , London , UK
| | - Elizabeth Jury
- Division of Medicine , Centre for Rheumatology Research, University College London, Rayne Institute , London , UK
| | - Lesley Mason
- Division of Medicine , Centre for Rheumatology Research, University College London, Rayne Institute , London , UK
| | | | - Lan Ni
- Department of Renal Medicine , University of Bristol , Bristol , UK
| | - Moin Saleem
- Department of Renal Medicine , University of Bristol , Bristol , UK
| | - Peter Mathieson
- Department of Renal Medicine , University of Bristol , Bristol , UK
| | - David Isenberg
- Division of Medicine , Centre for Rheumatology Research, University College London, Rayne Institute , London , UK
| | - Anisur Rahman
- Division of Medicine , Centre for Rheumatology Research, University College London, Rayne Institute , London , UK
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804
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Potter SS, Brunskill EW. Building an atlas of gene expression driving kidney development: pushing the limits of resolution. Pediatr Nephrol 2014; 29:581-8. [PMID: 23996451 PMCID: PMC7540944 DOI: 10.1007/s00467-013-2602-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Revised: 07/18/2013] [Accepted: 07/18/2013] [Indexed: 02/06/2023]
Abstract
Changing gene expression patterns is the essential driver of developmental processes. Growth factors, micro-RNAs, long intergenic noncoding RNAs, and epigenetic marks, such as DNA methylation and histone modifications, all work by impacting gene expression. The key features of developing cells, including their ability to communicate with others, are defined primarily by their gene-expression profiles. It is therefore clear that a gene-expression atlas of the developing kidney can provide a useful tool for the developmental nephrology research community. Toward this end, the GenitoUrinary Development Molecular Anatomy Project (GUDMAP) consortium has worked to create an atlas of the changing gene-expression patterns that drive kidney development. In this article, the global gene-expression profiling strategies of GUDMAP are reviewed. The initial work used laser-capture microdissection to purify multiple compartments of the developing kidney, including cap mesenchyme, renal vesicle, S-shaped bodies, proximal tubules, and more, which were then gene-expression profiled using microarrays. Resolution of the atlas was then improved by using transgenic mice with specific cell types labeled with green fluorescent protein (GFP), allowing their purification and profiling. In addition, RNA-Seq replaced microarrays. Currently, the atlas is being pushed to the single-cell resolution using microfluidic approaches that allow high-throughput RNA-Seq analysis of hundreds of individual cells. Results can identify novel types of cells and define interesting heterogeneities present within cell populations.
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Affiliation(s)
- S Steven Potter
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave, Cincinnati, OH, 45229, USA,
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805
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Affiliation(s)
- Kumar Sharma
- Division of Nephrology-Hypertension, Center for Renal Translational Medicine, Institute of Metabolomic Medicine, Department of Medicine, University of California, San Diego, California; andDivision of Nephrology-Hypertension, Veterans Affairs San Diego Healthcare System, Veterans Medical Research Foundation, San Diego, California
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806
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Pippin JW, Glenn ST, Krofft RD, Rusiniak ME, Alpers CE, Hudkins K, Duffield JS, Gross KW, Shankland SJ. Cells of renin lineage take on a podocyte phenotype in aging nephropathy. Am J Physiol Renal Physiol 2014; 306:F1198-209. [PMID: 24647714 DOI: 10.1152/ajprenal.00699.2013] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Aging nephropathy is characterized by podocyte depletion accompanied by progressive glomerulosclerosis. Replacement of terminally differentiated podocytes by local stem/progenitor cells is likely a critical mechanism for their regeneration. Recent studies have shown that cells of renin lineage (CoRL), normally restricted to the kidney's extraglomerular compartment, might serve this role after an abrupt depletion in podocyte number. To determine the effects of aging on the CoRL reserve and if CoRL moved from an extra- to the intraglomerular compartment during aging, genetic cell fate mapping was performed in aging Ren1cCre × Rs-ZsGreen reporter mice. Podocyte number decreased and glomerular scarring increased with advanced age. CoRL number decreased in the juxtaglomerular compartment with age. There was a paradoxical increase in CoRL in the intraglomerular compartment at 52 and 64 wk of age, where a subset coexpressed the podocyte proteins nephrin, podocin, and synaptopodin. Transmission electron microscopy studies showed that a subset of labeled CoRL in the glomerulus displayed foot processes, which attached to the glomerular basement membrane. No CoRL in the glomerular compartment stained for renin. These results suggest that, despite a decrease in the reserve, a subpopulation of CoRL moves to the glomerulus after chronic podocyte depletion in aging nephropathy, where they acquire a podocyte-like phenotype. This suggests that they might serve as adult podocyte stem/progenitor cells under these conditions, albeit in insufficient numbers to fully replace podocytes depleted with age.
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Affiliation(s)
- Jeffrey W Pippin
- Division of Nephrology, University of Washington, Seattle, Washington
| | - Sean T Glenn
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York; and
| | - Ronald D Krofft
- Division of Nephrology, University of Washington, Seattle, Washington
| | - Michael E Rusiniak
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York; and
| | - Charles E Alpers
- Department of Pathology, University of Washington, Seattle, Washington
| | - Kelly Hudkins
- Department of Pathology, University of Washington, Seattle, Washington
| | - Jeremy S Duffield
- Division of Nephrology, University of Washington, Seattle, Washington
| | - Kenneth W Gross
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York; and
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807
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Casalena G, Krick S, Daehn I, Yu L, Ju W, Shi S, Tsai SY, D'Agati V, Lindenmeyer M, Cohen CD, Schlondorff D, Bottinger EP. Mpv17 in mitochondria protects podocytes against mitochondrial dysfunction and apoptosis in vivo and in vitro. Am J Physiol Renal Physiol 2014; 306:F1372-80. [PMID: 24598802 DOI: 10.1152/ajprenal.00608.2013] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mitochondrial dysfunction is increasingly recognized as contributing to glomerular diseases, including those secondary to mitochondrial DNA (mtDNA) mutations and deletions. Mitochondria maintain cellular redox and energy homeostasis and are a major source of intracellular reactive oxygen species (ROS) production. Mitochondrial ROS accumulation may contribute to stress-induced mitochondrial dysfunction and apoptosis and thereby to glomerulosclerosis. In mice, deletion of the gene encoding Mpv17 is associated with glomerulosclerosis, but the underlying mechanism remains poorly defined. Here we report that Mpv17 localizes to mitochondria of podocytes and its expression is reduced in several glomerular injury models and in human focal segmental glomerulosclerosis (FSGS) but not in minimal change disease. Using models of mild or severe nephrotoxic serum nephritis (NTSN) in Mpv17(+/+) wild-type (WT) and Mpv17(-/-) knockout mice, we found that Mpv17 deficiency resulted in increased proteinuria (mild NTSN) and renal insufficiency (severe NTSN) compared with WT. These lesions were associated with increased mitochondrial ROS generation and mitochondrial injury such as oxidative DNA damage. In vitro, podocytes with loss of Mpv17 function were characterized by increased susceptibility to apoptosis and ROS injury including decreased mitochondrial function, loss of mtDNA content, and change in mitochondrial configuration. In summary, the inner mitochondrial membrane protein Mpv17 in podocytes is essential for the maintenance of mitochondrial homeostasis and protects podocytes against oxidative stress-induced injury both in vitro and in vivo.
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Affiliation(s)
- Gabriela Casalena
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Stefanie Krick
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Ilse Daehn
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Liping Yu
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Wenjun Ju
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Shaolin Shi
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Su-yi Tsai
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Vivette D'Agati
- Department of Pathology, Columbia University, College of Physicians and Surgeons, New York, New York; and
| | - Maja Lindenmeyer
- Division of Nephrology and Institute of Physiology with Center of Integrative Human Physiology, University Hospital and University of Zurich, Zurich, Switzerland
| | - Clemens D Cohen
- Division of Nephrology and Institute of Physiology with Center of Integrative Human Physiology, University Hospital and University of Zurich, Zurich, Switzerland
| | - Detlef Schlondorff
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Erwin P Bottinger
- Division of Nephrology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York; Charles Bronfman Institute for Personalized Medicine, Icahn School of Medicine at Mount Sinai, New York, New York;
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808
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Wilson C, Dryer SE. A mutation in TRPC6 channels abolishes their activation by hypoosmotic stretch but does not affect activation by diacylglycerol or G protein signaling cascades. Am J Physiol Renal Physiol 2014; 306:F1018-25. [PMID: 24598806 DOI: 10.1152/ajprenal.00662.2013] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Canonical transient receptor potential-6 (TRPC6) channels have been implicated in the pathogenesis of kidney disease and in the regulation of vascular smooth muscle tone, podocyte function, and a variety of processes in other cell types. The question of whether their gating is intrinsically mechanosensitive has been controversial. In this study we have examined activation of two alleles of TRPC6 transiently expressed in CHO-K1 cells: the wild-type human TRPC6 channel, and TRPC6-N143S, an allele originally identified in a family with autosomal dominant familial focal and segmental glomerulosclerosis (FSGS). We observed that both channel variants carried robust cationic currents that could be evoked by application of membrane-permeable analogs of diacylglycerol (DAG) or by the P2Y receptor agonist ATP. The amplitudes and characteristics of currents evoked by the DAG analog or ATP were indistinguishable in cells expressing the two TRPC6 alleles. By contrast, hypoosmotic stretch evoked robust currents in wild-type TRPC6 channels but had no discernible effect on currents in cells expressing TRPC6-N143S, indicating that the mutant form lacks mechanosensitivity. Coexpression of TRPC6-N143S with wild-type TRPC6 or TRPC3 channels did not alter stretch-evoked responses compared with when TRPC3 channels were expressed by themselves, indicating that TRPC6-N143S does not function as a dominant-negative. These data indicate that mechanical activation and activation evoked by DAG or ATP occur through fundamentally distinct biophysical mechanisms, and they provide support for the hypothesis that protein complexes containing wild-type TRPC6 subunits can be intrinsically mechanosensitive.
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Affiliation(s)
- Cory Wilson
- Dept. of Biology and Biochemistry, Univ. of Houston, 4800 Calhoun, Houston, TX, 77204-5001.
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809
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Wang Y, Yu F, Song D, Wang SX, Zhao MH. Podocyte involvement in lupus nephritis based on the 2003 ISN/RPS system: a large cohort study from a single centre. Rheumatology (Oxford) 2014; 53:1235-44. [PMID: 24599917 DOI: 10.1093/rheumatology/ket491] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVE The podocyte lesion in LN is still an intriguing controversy. We assess the associations between podocyte lesions and clinico-pathological features in a large cohort of LN patients. METHODS The clinico-pathological data of 202 patients with renal biopsy-proven LN were retrospectively studied. The degree of podocyte lesions was assessed morphologically and its correlations with clinico-pathological parameters were further analysed. RESULTS The podocyte foot processes of most LN patients significantly effaced, reflected by the median foot process width (FPW) of 1397.39 nm, and 13 patients met the histological criteria of lupus podocytopathy. The FPW was correlated with proteinuria (r = 0.509, P < 0.001) and the cut-off value of FPW, >1240 nm, could differentiate nephrotic proteinuria from non-nephrotic proteinuria with sensitivity 81.5% and specificity 62.7%. The FPW varied significantly with different types of LN, and the patients with combined LN presented with the most severe lesions. The complete remission rate was significantly higher and the long-term renal outcome was better in the group with calcineurin inhibitors than that with other regimens in patients with FPW >1240 nm. CONCLUSION Podocyte damage was common in LN. Pure lupus podocytopathy might act as an extreme form of lupus podocyte lesion, and more patients might present with severe podocyte effacement concealed in different types of LN, which needs further investigation.
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Affiliation(s)
- Yan Wang
- Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China
| | - Feng Yu
- Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.
| | - Di Song
- Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China
| | - Su-Xia Wang
- Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China
| | - Ming-Hui Zhao
- Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China.Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China and Peking-Tsinghua Center for Life Sciences, Beijing, P.R. China
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810
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Xie X, Colberg-Poley AM, Das JR, Li J, Zhang A, Tang P, Jerebtsova M, Gutkind JS, Ray PE. The basic domain of HIV-tat transactivating protein is essential for its targeting to lipid rafts and regulating fibroblast growth factor-2 signaling in podocytes isolated from children with HIV-1-associated nephropathy. J Am Soc Nephrol 2014; 25:1800-13. [PMID: 24578133 DOI: 10.1681/asn.2013070710] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Podocyte injury has a critical role in the pathogenesis of HIV-associated nephropathy (HIVAN). The HIV-1 transactivator of transcription (Tat), combined with fibroblast growth factor-2 (FGF-2), can induce the dedifferentiation and proliferation of cultured human podocytes. Cellular internalization of Tat requires interactions with heparan sulfate proteoglycans and cholesterol-enriched lipid rafts (LRs). However, the specific distribution of Tat in human podocytes and its ability to associate with LRs have not been documented. Here, we found that Tat is preferentially recruited to LRs in podocytes isolated from children with HIVAN. Furthermore, we identified arginines in the basic domain (RKKRRQRRR) of Tat as essential for (1) targeting Tat to LRs, (2) Tat-mediated increases in the expression of Rho-A and matrix metalloproteinase-9 in LRs, and (3) Tat-mediated enhancement of FGF-2 signaling in human podocytes and HIV-transgenic mouse kidneys and the exacerbation of renal lesions in these mice. Tat carrying alanine substitutions in the basic domain (AKKAAQAAA) remained localized in the cytosol and did not associate with LRs or enhance FGF-2 signaling in cultured podocytes. These results show the specific association of Tat with LRs in podocytes isolated from children with HIVAN, confirm Tat as a regulator of FGF-2 signaling in LRs, and identify the key domain of Tat responsible for promoting these effects and aggravating renal injury in HIV-transgenic mice. Moreover, these results provide a molecular framework for developing novel therapies to improve the clinical outcome of children with HIVAN.
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Affiliation(s)
| | - Anamaris M Colberg-Poley
- Center for Genetic Medicine Research and Department of Pediatrics, George Washington University, Washington, DC; and
| | | | | | | | - Pingtao Tang
- Center for Genetic Medicine Research and Department of Pediatrics, George Washington University, Washington, DC; and
| | - Marina Jerebtsova
- Center for Genetic Medicine Research and Department of Pediatrics, George Washington University, Washington, DC; and
| | - J Silvio Gutkind
- Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland
| | - Patricio E Ray
- Center for Genetic Medicine Research and Department of Pediatrics, George Washington University, Washington, DC; and Division of Nephrology, Children's National Medical Center, Washington, DC;
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811
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Locatelli M, Buelli S, Pezzotta A, Corna D, Perico L, Tomasoni S, Rottoli D, Rizzo P, Conti D, Thurman JM, Remuzzi G, Zoja C, Morigi M. Shiga toxin promotes podocyte injury in experimental hemolytic uremic syndrome via activation of the alternative pathway of complement. J Am Soc Nephrol 2014; 25:1786-98. [PMID: 24578132 DOI: 10.1681/asn.2013050450] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Shiga toxin (Stx)-producing Escherichia coli is the offending agent of postdiarrhea-associated hemolytic uremic syndrome (HUS), a disorder of glomerular ischemic damage and widespread microvascular thrombosis. We previously documented that Stx induces glomerular complement activation, generating C3a responsible for microvascular thrombosis in experimental HUS. Here, we show that the presence of C3 deposits on podocytes is associated with podocyte damage and loss in HUS mice generated by the coinjection of Stx2 and LPS. Because podocyte adhesion to the glomerular basement membrane is mediated by integrins, the relevance of integrin-linked kinase (ILK) signals in podocyte dysfunction was evaluated. Podocyte expression of ILK increased after the injection of Stx2/LPS and preceded the upregulation of Snail and downregulation of nephrin and α-actinin-4. Factor B deficiency or pretreatment with an inhibitory antibody to factor B protected mice against Stx2/LPS-induced podocyte dysregulation. Similarly, pretreatment with a C3a receptor antagonist limited podocyte loss and changes in ILK, Snail, and α-actinin-4 expression. In cultured podocytes, treatment with C3a reduced α-actinin-4 expression and promoted ILK-dependent nuclear expression of Snail and cell motility. These results suggest that Stx-induced activation of the alternative pathway of complement and generation of C3a promotes ILK signaling, leading to podocyte dysfunction and loss in Stx-HUS.
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Affiliation(s)
- Monica Locatelli
- IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri," Centro Anna Maria Astori, Bergamo, Italy
| | - Simona Buelli
- IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri," Centro Anna Maria Astori, Bergamo, Italy
| | - Anna Pezzotta
- IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri," Centro Anna Maria Astori, Bergamo, Italy
| | - Daniela Corna
- IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri," Centro Anna Maria Astori, Bergamo, Italy
| | - Luca Perico
- IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri," Centro Anna Maria Astori, Bergamo, Italy
| | - Susanna Tomasoni
- IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri," Centro Anna Maria Astori, Bergamo, Italy
| | - Daniela Rottoli
- IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri," Centro Anna Maria Astori, Bergamo, Italy
| | - Paola Rizzo
- IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri," Centro Anna Maria Astori, Bergamo, Italy
| | - Debora Conti
- IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri," Centro Anna Maria Astori, Bergamo, Italy
| | - Joshua M Thurman
- Division of Nephrology and Hypertension, University of Colorado Denver School of Medicine, Aurora, Colorado; and
| | - Giuseppe Remuzzi
- IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri," Centro Anna Maria Astori, Bergamo, Italy; Unit of Nephrology and Dialysis, Azienda Ospedaliera Papa Giovanni XXIII, Bergamo, Italy
| | - Carlamaria Zoja
- IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri," Centro Anna Maria Astori, Bergamo, Italy
| | - Marina Morigi
- IRCCS - Istituto di Ricerche Farmacologiche "Mario Negri," Centro Anna Maria Astori, Bergamo, Italy;
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812
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Roshanravan H, Dryer SE. ATP acting through P2Y receptors causes activation of podocyte TRPC6 channels: role of podocin and reactive oxygen species. Am J Physiol Renal Physiol 2014; 306:F1088-97. [PMID: 24553432 DOI: 10.1152/ajprenal.00661.2013] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Extracellular ATP may contribute to Ca(2+) signaling in podocytes during tubuloglomerular feedback (TGF) and possibly as a result of local tissue damage. TRPC6 channels are Ca(2+)-permeable cationic channels that have been implicated in the pathophysiology of podocyte diseases. Here we show using whole cell recordings that ATP evokes robust activation of TRPC6 channels in mouse podocyte cell lines and in rat podocytes attached to glomerular capillaries in ex vivo glomerular explants. The EC50 for ATP is ~10 μM and is maximal at 100 μM, and currents were blocked by the P2 antagonist suramin. In terms of maximal currents that can be evoked, ATP is the strongest activator of podocyte TRPC6 that we have characterized to date. Smaller currents were observed in response to ADP, UTP, and UDP. ATP-evoked currents in podocytes were abolished by TRPC6 knockdown and by pretreatment with 10 μM SKF-96365 or 50 μM La(3+). ATP effects were also abolished by inhibiting G protein signaling and by the PLC/PLA2 inhibitor D-609. ATP effects on TRPC6 were also suppressed by knockdown of the slit diaphragm scaffolding protein podocin, and also by tempol, a membrane-permeable quencher of reactive oxygen species. Modulation of podocyte TRPC6 channels, especially in foot processes, could provide a mechanism for regulation of glomerular function by extracellular nucleotides, possibly leading to changes in permeation through slit diaphragms. These results raise the possibility that sustained ATP signaling could contribute to foot process effacement, Ca(2+)-dependent changes in gene expression, and/or detachment of podocytes.
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Affiliation(s)
- Hila Roshanravan
- Dept. of Biology and Biochemistry, Univ. of Houston, Houston, TX 77204-5001.
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813
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Abstract
Macroautophagy is a highly evolutionally conserved degradation process by which cytosolic materials (including macromolecules such as proteins and lipids) and damaged organelles are broken down to their basic components. The role of autophagy is not only the elimination of materials, but it also serves as a dynamic recycling system that produces new components and energy for cellular renovation and homeostasis. The association of autophagy with the organ physiology and pathogenesis of various disorders such as neurodegenerative diseases, cancer, infection and inflammatory bowel disease has been revealed in recent years. Autophagy also plays an essential role in cellular homeostasis in kidney and counteracts age-related stress and kidney diseases. Here, we critically review the current evidence regarding autophagy in the kidney, in particular as assessed with tissue- or cell lineage-specific autophagy-deficient mice. Better insight into the mechanisms underlying renoprotective roles of autophagy will pave the way toward novel therapies for kidney diseases.
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Affiliation(s)
- Yoshitsugu Takabatake
- Department of Geriatric Medicine and Nephrology (B6), Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Tomonori Kimura
- Department of Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, NM, USA
| | - Atsushi Takahashi
- Department of Geriatric Medicine and Nephrology (B6), Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Yoshitaka Isaka
- Department of Geriatric Medicine and Nephrology (B6), Osaka University Graduate School of Medicine, Suita, Osaka, Japan
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814
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Bi J, Pellenz CD, Krendel M. Visualization of cytoskeletal dynamics in podocytes using adenoviral vectors. Cytoskeleton (Hoboken) 2014; 71:145-56. [PMID: 24415679 DOI: 10.1002/cm.21162] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 01/03/2014] [Indexed: 02/01/2023]
Abstract
Glomerular visceral epithelial cells (podocytes) play a key role in maintaining selective protein filtration in the kidney. Podocytes have a complex cell shape characterized by the presence of numerous actin-rich processes, which cover the surface of glomerular capillaries and are connected by specialized cell-cell adhesion complexes (slit diaphragms). Human genetic studies and experiments in knockout mouse models show that actin filaments and actin-associated proteins are indispensable for the maintenance of podocyte shape, slit diaphragm integrity, and normal glomerular filtration. The ability to examine cytoskeletal protein organization and dynamics in podocytes and to test the effects of disease-associated mutations on protein localization provides valuable information for researchers aiming to dissect the molecular mechanisms of podocyte dysfunction. We describe how adenovirus-mediated transduction of cultured podocytes with DNA constructs can be used to reliably introduce fluorescently tagged cytoskeletal markers for live cell imaging with high efficiency and low toxicity. This technique can be used to study the dynamic reorganization of the podocyte cytoskeleton and to test the effects of novel mutations on podocyte cytoskeletal dynamics.
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Affiliation(s)
- Jing Bi
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York
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815
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Abstract
Cells possess adaptive biosynthetic systems to maintain cellular energy levels for survival under adverse environmental conditions. Autophagy is an evolutionarily conserved cellular catabolic process that breaks down and recycles cytosolic material including macromolecules and organelles through lysosomal degradation. This catabolic process, represented by macroautophagy, is induced by a variety of cellular stresses such as nutrient starvation, which causes a shortage of cellular energy for cells to maintain cellular homeostasis and essential biological activities. In contrast, upon nutrient availability, cells stimulate anabolic processes. The mechanistic/mammalian target of rapamycin, a serine/threonine protein kinase, is a key player in stimulating cellular anabolism in response to nutrients and growth factors, and plays a crucial role in suppressing autophagy activity. Growing evidence has suggested that autophagy activity is required for the maintenance and physiological functions of renal cells including proximal tubular cells and podocytes. In this article, we discuss recent progress in the regulation of autophagy by mechanistic/mammalian target of rapamycin signaling.
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Affiliation(s)
- Ken Inoki
- Life Sciences Institute, Department of Molecular and Integrative Physiology, Division of Nephrology, Department of Internal Medicine, University of Michigan, Ann Arbor, MI.
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816
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Abstract
Podocyte injury and loss critically contribute to the pathogenesis of proteinuric kidney diseases including diabetic nephropathy. Deregulated lipid metabolism with disturbed free fatty acid (FFA) metabolism is a characteristic of metabolically unhealthy obesity and type 2 diabetes and likely contributes to end-stage kidney disease irrespective of the underlying kidney disease. In the current review, we summarize recent findings related to FFAs and altered renal FFA metabolism with a special focus on podocytes. We will outline the opposing effects of saturated and monounsaturated FFAs and a particular emphasis will be given to the underlying molecular mechanisms involving insulin resistance and endoplasmic reticulum homeostasis. Finally, recent data suggesting a critical role of renal FFA metabolism to adapt to an altered lipid environment will be discussed.
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Affiliation(s)
- Jonas Sieber
- Division of Nephrology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
- *Correspondence: Jonas Sieber, Division of Nephrology, Massachusetts General Hospital, Harvard Medical School, 149 13th Street, Charlestown, MA 02129, USA e-mail: ; Andreas Werner Jehle, Department of Biomedicine, Molecular Nephrology, University Hospital Basel, Room 303, Hebelstrasse 20, Basel 4031, Switzerland e-mail:
| | - Andreas Werner Jehle
- Molecular Nephrology, Department of Biomedicine, University Hospital Basel, Basel, Switzerland
- Transplantation Immunology and Nephrology, Department of Internal Medicine, University Hospital Basel, Basel, Switzerland
- *Correspondence: Jonas Sieber, Division of Nephrology, Massachusetts General Hospital, Harvard Medical School, 149 13th Street, Charlestown, MA 02129, USA e-mail: ; Andreas Werner Jehle, Department of Biomedicine, Molecular Nephrology, University Hospital Basel, Room 303, Hebelstrasse 20, Basel 4031, Switzerland e-mail:
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817
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Abstract
Podocytes are specialized epithelial cells that cover the outer surfaces of glomerular capillaries. Unique cell junctions, known as slit diaphragms, which feature nephrin and Neph family proteins in addition to components of adherens, tight, and gap junctions, connect adjacent podocyte foot processes. Single gene disorders affecting the slit diaphragm result in nephrotic syndrome in humans, characterized by massive loss of protein across the capillary wall. In addition to specialized cell junctions, interconnecting podocytes also adhere to the glomerular basement membrane (GBM) of the capillary wall. The GBM is a dense network of secreted, extracellular matrix (ECM) components and contains tissue-restricted isoforms of collagen IV and laminin in addition to other structural proteins and ECM regulators such as proteases and growth factors. The specialized niche of the GBM provides a scaffold for endothelial cells and podocytes to support their unique functions and human genetic mutations in GBM components lead to renal failure, thus highlighting the importance of cell-matrix interactions in the glomerulus. Cells adhere to ECM via adhesion receptors, including integrins, syndecans, and dystroglycan and in particular the integrin heterodimer α3β1 is required to maintain barrier integrity. Therefore, the sophisticated function of glomerular filtration relies on podocyte adhesion both at cell junctions and at the interface with the ECM. In health, the podocyte coordinates signals from cell junctions and cell-matrix interactions, in response to environmental cues in order to regulate filtration and as our understanding of mechanisms that control cell adhesion in the glomerulus develops, then insight into the effects of disease will improve. The ultimate goal will be to develop targeted therapies to prevent or repair defects in the filtration barrier and to restore glomerular function.
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Affiliation(s)
- Rachel Lennon
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, The University of Manchester, Manchester, UK
- Institute of Human Development, Faculty of Medical and Human Sciences, The University of Manchester, Manchester, UK
- Department of Paediatric Nephrology, Manchester Academic Health Science Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK
- *Correspondence: Rachel Lennon, Wellcome Trust Centre for Cell-Matrix Research, The University of Manchester, Michael Smith Building, Manchester M13 9PT, UK e-mail:
| | - Michael J. Randles
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, The University of Manchester, Manchester, UK
- Institute of Human Development, Faculty of Medical and Human Sciences, The University of Manchester, Manchester, UK
| | - Martin J. Humphries
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, The University of Manchester, Manchester, UK
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818
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Abstract
Sphingolipids are components of the lipid rafts in plasma membranes, which are important for proper function of podocytes, a key element of the glomerular filtration barrier. Research revealed an essential role of sphingolipids and sphingolipid metabolites in glomerular disorders of genetic and non-genetic origin. The discovery that glucocerebrosides accumulate in Gaucher disease in glomerular cells and are associated with clinical proteinuria initiated intensive research into the function of other sphingolipids in glomerular disorders. The accumulation of sphingolipids in other genetic diseases including Tay-Sachs, Sandhoff, Fabry, hereditary inclusion body myopathy 2, Niemann-Pick, and nephrotic syndrome of the Finnish type and its implications with respect to glomerular pathology will be discussed. Similarly, sphingolipid accumulation occurs in glomerular diseases of non-genetic origin including diabetic kidney disease (DKD), HIV-associated nephropathy, focal segmental glomerulosclerosis (FSGS), and lupus nephritis. Sphingomyelin metabolites, such as ceramide, sphingosine, and sphingosine-1-phosphate have also gained tremendous interest. We recently described that sphingomyelin phosphodiesterase acid-like 3b (SMPDL3b) is expressed in podocytes where it modulates acid sphingomyelinase activity and acts as a master modulator of danger signaling. Decreased SMPDL3b expression in post-reperfusion kidney biopsies from transplant recipients with idiopathic FSGS correlates with the recurrence of proteinuria in patients and in experimental models of xenotransplantation. Increased SMPDL3b expression is associated with DKD. The consequences of differential SMPDL3b expression in podocytes in these diseases with respect to their pathogenesis will be discussed. Finally, the role of sphingolipids in the formation of lipid rafts in podocytes and their contribution to the maintenance of a functional slit diaphragm in the glomerulus will be discussed.
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Affiliation(s)
- Sandra Merscher
- Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology, Department of Medicine, University of Miami, Miami, FL, USA
- *Correspondence: Sandra Merscher, Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology, Department of Medicine, University of Miami, 1580 NW 10th Avenue, Batchelor Building, Room 628, Miami, FL 33136, USA e-mail: ; Alessia Fornoni, Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology, Department of Medicine, University of Miami, 1580 NW 10th Avenue, Batchelor Building, Room 633, Miami, FL 33136, USA e-mail:
| | - Alessia Fornoni
- Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology, Department of Medicine, University of Miami, Miami, FL, USA
- *Correspondence: Sandra Merscher, Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology, Department of Medicine, University of Miami, 1580 NW 10th Avenue, Batchelor Building, Room 628, Miami, FL 33136, USA e-mail: ; Alessia Fornoni, Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology, Department of Medicine, University of Miami, 1580 NW 10th Avenue, Batchelor Building, Room 633, Miami, FL 33136, USA e-mail:
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819
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Abstract
The evaluation and treatment of the heterogeneous group of kidney diseases poses a challenging field in pediatrics. Many of the pediatric disorders resulting in severe renal affection are exceedingly rare and therapeutic approaches have remained symptomatic for most of these disease entities. The insights obtained from cellular and molecular studies of rare disorders by recent genetic studies have now substantially changed our mechanistic understanding of various important pediatric renal diseases and positive examples of targeted treatment approaches are emerging. Three fields of recent breathtaking developments in pediatric nephrology are the pathophysiology of nephrotic syndrome and proteinuria, the molecular mechanisms underlying atypical hemolytic uremic syndrome, and the genetics and cellular biology of inherited cystic kidney diseases. In all three areas, the combined power of molecular basic science together with deeply characterizing clinical approaches has led to the establishment of novel pathophysiological principles and to the first clinical trials of targeted treatment approaches.
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Affiliation(s)
- Max Christoph Liebau
- Department of Pediatrics and Center for Molecular Medicine, University Hospital of Cologne , Cologne , Germany ; Nephrology Research Laboratory, Department II of Internal Medicine, University Hospital of Cologne , Cologne , Germany
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820
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Abstract
Proper podocyte function within the glomerulus demands a high and continuous energy supply that is mainly derived from the respiratory chain of the inner mitochondrial membrane. Dysregulations in the metabolic homeostasis of podocytes may result in podocyte damage and glomerular disease. This article highlights the current knowledge about podocyte energy supply by the respiratory chain. We review the regulation of mitochondrial oxidative metabolism with regard to podocytopathy and discuss the latest understanding of different mitochondrial dysfunctions of the podocyte in diabetic nephropathy and focal segmental glomerulosclerosis (FSGS). We discuss genetic forms of mitochondriopathy of the podocyte and end with recent knowledge about crosstalk between NADH and NADPH and potential therapeutic options for podocyte mitochondriopathy. We aim to raise awareness for the complex and interesting mechanisms of podocyte damage by impaired energy supply that, despite of novel findings in recent years, is poorly understood so far.
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Affiliation(s)
- Janina Müller-Deile
- Division of Nephrology and Hypertension, Department of Medicine, Hannover Medical School, Hannover, Germany
| | - Mario Schiffer
- Division of Nephrology and Hypertension, Department of Medicine, Hannover Medical School, Hannover, Germany
- *Correspondence: Mario Schiffer, Division of Nephrology, Hannover Medical School, Carl-Neuberg-Str. 1, Hannover 30625, Germany e-mail:
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821
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Merscher S, Pedigo CE, Mendez AJ. Metabolism, energetics, and lipid biology in the podocyte - cellular cholesterol-mediated glomerular injury. Front Endocrinol (Lausanne) 2014; 5:169. [PMID: 25352833 PMCID: PMC4196552 DOI: 10.3389/fendo.2014.00169] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Accepted: 09/28/2014] [Indexed: 12/12/2022] Open
Abstract
Chronic kidney disease (CKD) is associated with a high risk of death. Dyslipidemia is commonly observed in patients with CKD and is accompanied by a decrease in plasma high-density lipoprotein, and an increase in plasma triglyceride-rich lipoproteins and oxidized lipids. The observation that statins may decrease albuminuria but do not stop the progression of CKD indicates that pathways other than the cholesterol synthesis contribute to cholesterol accumulation in the kidneys of patients with CKD. Recently, it has become clear that increased lipid influx and impaired reverse cholesterol transport can promote glomerulosclerosis, and tubulointerstitial damage. Lipid-rafts are cholesterol-rich membrane domains with important functions in regulating membrane fluidity, membrane protein trafficking, and in the assembly of signaling molecules. In podocytes, which are specialized cells of the glomerulus, they contribute to the spatial organization of the slit diaphragm (SD) under physiological and pathological conditions. The discovery that podocyte-specific proteins such as podocin can bind and recruit cholesterol contributing to the formation of the SD underlines the importance of cholesterol homeostasis in podocytes and suggests cholesterol as an important regulator in the development of proteinuric kidney disease. Cellular cholesterol accumulation due to increased synthesis, influx, or decreased efflux is an emerging concept in podocyte biology. This review will focus on the role of cellular cholesterol accumulation in the pathogenesis of kidney diseases with a focus on glomerular diseases.
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Affiliation(s)
- Sandra Merscher
- Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology and Hypertension, Department of Medicine, University of Miami, Miami, FL, USA
- *Correspondence: Sandra Merscher, Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology and Hypertension, Department of Medicine, University of Miami,1580 NW 10th Ave, Batchelor Bldg, Room 628, Miami, FL 33136, USA e-mail:
| | - Christopher E. Pedigo
- Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology and Hypertension, Department of Medicine, University of Miami, Miami, FL, USA
| | - Armando J. Mendez
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Diabetes Research Institute, University of Miami, Miami, FL, USA
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822
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Abstract
Diabetes mellitus (DM) is the most common cause of chronic kidney disease and end stage renal disease. New onset diabetes mellitus after transplant (NODAT) has been described in approximately 30% of non-diabetic kidney-transplant recipients many years post transplantation. DM in patients with kidney transplantation constitutes a major comorbidity, and has significant impact on the patients and allografts' outcome. In addition to the major comorbidity and mortality that result from cardiovascular and other DM complications, long standing DM after kidney-transplant has significant pathological injury to the allograft, which results in lowering the allografts and the patients' survivals. In spite of the cumulative body of data on diabetic nephropathy (DN) in the native kidney, there has been very limited data on the DN in the transplanted kidney. In this review, we will shed the light on the risk factors that lead to the development of NODAT. We will also describe the impact of DM on the transplanted kidney, and the outcome of kidney-transplant recipients with NODAT. Additionally, we will present the most acceptable data on management of NODAT.
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Affiliation(s)
- Vasil Peev
- Department of Medicine, Rush University School of Medicine, Chicago, IL, USA
| | - Jochen Reiser
- Department of Medicine, Rush University School of Medicine, Chicago, IL, USA
- *Correspondence: Jochen Reiser, Rush University Medical Center, 1735 West Harrison Street, Cohn Building, Suite 724, Chicago, IL 60612, USA e-mail:
| | - Nada Alachkar
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
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823
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Laurin M, Dumouchel A, Fukui Y, Côté JF. The Rac-specific exchange factors Dock1 and Dock5 are dispensable for the establishment of the glomerular filtration barrier in vivo. Small GTPases 2013; 4:221-30. [PMID: 24365888 DOI: 10.4161/sgtp.27430] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Podocytes are specialized kidney cells that form the kidney filtration barrier through the connection of their foot processes. Nephrin and Neph family transmembrane molecules at the surface of podocytes interconnect to form a unique type of cell-cell junction, the slit diaphragm, which acts as a molecular sieve. The cytoplasmic tails of Nephrin and Neph mediate cytoskeletal rearrangement that contributes to the maintenance of the filtration barrier. Nephrin and Neph1 orthologs are essential to regulate cell-cell adhesion and Rac-dependent actin rearrangement during Drosophila myoblast fusion. We hypothesized here that molecules regulating myoblast fusion in Drosophila could contribute to signaling downstream of Nephrin and Neph1 in podocytes. We found that Nephrin engagement promoted recruitment of the Rac exchange factor Dock1 to the membrane. Furthermore, Nephrin overexpression led to lamellipodia formation that could be blocked by inhibiting Rac1 activity. We generated in vivo mouse models to investigate whether Dock1 and Dock5 contribute to the formation and maintenance of the kidney filtration barrier. Our results indicate that while Dock1 and Dock5 are expressed in podocytes, their functions are not essential for the development of the glomerular filtration barrier. Furthermore, mice lacking Dock1 were not protected from LPS-induced podocyte effacement. Our data suggest that Dock1 and Dock5 are not the important exchange factors regulating Rac activity during the establishment and maintenance of the glomerular barrier.
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Affiliation(s)
- Mélanie Laurin
- Institut de Recherches Cliniques de Montréal (IRCM); Montréal, QC, Canada; Département de Médecine (Programmes de Biologie Moléculaire); Université de Montréal; Montréal, QC, Canada
| | - Annie Dumouchel
- Institut de Recherches Cliniques de Montréal (IRCM); Montréal, QC, Canada
| | - Yoshinori Fukui
- Division of Immunogenetics; Department of Immunobiology and Neuroscience; Medical Institute of Bioregulation; Kyushu University; Fukuoda, Japan
| | - Jean-François Côté
- Institut de Recherches Cliniques de Montréal (IRCM); Montréal, QC, Canada; Département de Médecine (Programmes de Biologie Moléculaire); Université de Montréal; Montréal, QC, Canada; Département de Biochimie; Université de Montréal; Montréal, QC, Canada; Division of Experimental Medicine; McGill University; Montréal, QC, Canada
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824
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Rezende GM, Viana VS, Malheiros DMAC, Borba EF, Silva NAS, Silva C, Leon EP, Noronha IL, Bonfa E. Podocyte injury in pure membranous and proliferative lupus nephritis: distinct underlying mechanisms of proteinuria? Lupus 2013; 23:255-62. [PMID: 24356611 DOI: 10.1177/0961203313517152] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Proteinuria is a major feature of lupus nephritis (LN) and reflects podocyte injury. Analysis of podocyte biomarkers was performed attempting to identify if podocyte phenotype is distinct in pure membranous and proliferative LN. Expression of synaptopodin, Wilms tumor protein 1 (WT1), glomerular epithelial protein 1 (GLEPP1) and nephrin was evaluated in 52 LN biopsies by immunohistochemistry. Preserved synaptopodin expression was observed in only 10 (19.2%) of all biopsies while 42 (80.8%) had reduced expression. Both groups had comparable proteinuria at the time of biopsy (p = 0.22); however, in the mean follow-up of four years there was a tendency toward lower mean levels of proteinuria in patients with preserved synaptopodin staining (0.26±0.23 vs. 0.84±0.90 g/24 h, p = 0.05) compared with those with diminished expression. Thirty-nine (75%) biopsies were classified as proliferative and 13 (25%) as pure membranous. Comparison of podocyte biomarkers demonstrated a predominance of preserved staining of synaptopodin (69.2%), WT1 (69.2%), GLEPP1 (53.9%) and nephrin (60%) in the pure membranous group whereas only <10% of the proliferative showed preserved expression. Our data suggest that in proliferative forms there seems to occur structural podocyte damage, whereas in the pure membranous the predominant preserved pattern suggests a dysfunctional podocyte lesion that may account for the better long-term prognosis of proteinuria outcome.
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Affiliation(s)
- G M Rezende
- 1Division of Rheumatology; Department of Pathology; and Laboratory of Cellular, Genetic, and Molecular Nephrology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
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825
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Poveda J, Tabara LC, Fernandez-Fernandez B, Martin-Cleary C, Sanz AB, Selgas R, Ortiz A, Sanchez-Niño MD. TWEAK/Fn14 and Non-Canonical NF-kappaB Signaling in Kidney Disease. Front Immunol 2013; 4:447. [PMID: 24339827 PMCID: PMC3857575 DOI: 10.3389/fimmu.2013.00447] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 11/26/2013] [Indexed: 12/27/2022] Open
Abstract
The incidence of acute kidney injury (AKI) and chronic kidney disease (CKD) is increasing. However, there is no effective therapy for AKI and current approaches only slow down, but do not prevent progression of CKD. TWEAK is a TNF superfamily cytokine. A solid base of preclinical data suggests a role of therapies targeting the TWEAK or its receptor Fn14 in AKI and CKD. In particular TWEAK/Fn14 targeting may preserve renal function and decrease cell death, inflammation, proteinuria, and fibrosis in mouse animal models. Furthermore there is clinical evidence for a role of TWEAK in human kidney injury including increased tissue and/or urinary levels of TWEAK and parenchymal renal cell expression of the receptor Fn14. In this regard, clinical trials of TWEAK targeting are ongoing in lupus nephritis. Nuclear factor-kappa B (NF-κB) activation plays a key role in TWEAK-elicited inflammatory responses. Activation of the non-canonical NF-κB pathway is a critical difference between TWEAK and TNF. TWEAK activation of the non-canonical NF-κB pathways promotes inflammatory responses in tubular cells. However, there is an incomplete understanding of the role of non-canonical NF-κB activation in kidney disease and on its contribution to TWEAK actions in vivo.
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Affiliation(s)
- Jonay Poveda
- Department of Nephrology, IIS-Fundacion Jimenez Diaz, Universidad Autonoma de Madrid and IRSIN , Madrid , Spain
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826
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Abstract
It is becoming increasingly clear that the insulin responses of a number of different cell types within the kidney are important in the maintenance of normal renal function. This review summarizes our current understanding of renal insulin signalling, with specific focus on the podocyte, presenting recent evidence that suggests these responses are altered in systemic insulin-resistant states and chronic kidney disease via a number of different mechanisms.
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Affiliation(s)
- Abigail Lay
- Academic Renal Unit, Learning and Research Building, Southmead Hospital, School of Clinical Sciences, University of Bristol, Bristol BS10 5NB, UK
| | - Richard J Coward
- Academic Renal Unit, Learning and Research Building, Southmead Hospital, School of Clinical Sciences, University of Bristol, Bristol BS10 5NB, UK
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827
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Das R, Xu S, Quan X, Nguyen TT, Kong ID, Chung CH, Lee EY, Cha SK, Park KS. Upregulation of mitochondrial Nox4 mediates TGF-β-induced apoptosis in cultured mouse podocytes. Am J Physiol Renal Physiol 2013; 306:F155-67. [PMID: 24259511 DOI: 10.1152/ajprenal.00438.2013] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Injury to podocytes leads to the onset of chronic renal diseases characterized by proteinuria. Elevated transforming growth factor (TGF)-β in kidney tissue is associated with podocyte damage that ultimately results in apoptosis and detachment. We investigated the proapoptotic mechanism of TGF-β in immortalized mouse podocytes. Exogenous TGF-β1-induced podocyte apoptosis through caspase-3 activation, which was related to elevated ROS levels generated by selective upregulation of NADPH oxidase 4 (Nox4). In mouse podocytes, Nox4 was predominantly localized to mitochondria, and Nox4 upregulation by TGF-β1 markedly depolarized mitochondrial membrane potential. TGF-β1-induced ROS production and caspase activation were mitigated by an antioxidant, the Nox inhibitor diphenyleneiodonium, or small interfering RNA for Nox4. A TGF-β receptor I blocker, SB-431542, completely reversed the changes triggered by TGF-β1. Knockdown of either Smad2 or Smad3 prevented the increase of Nox4 expression, ROS generation, loss of mitochondrial membrane potential, and caspase-3 activation by TGF-β1. These results suggest that TGF-β1-induced mitochondrial Nox4 upregulation via the TGF-β receptor-Smad2/3 pathway is responsible for ROS production, mitochondrial dysfunction, and apoptosis, which may at least in part contribute to the development and progression of proteinuric glomerular diseases such as diabetic nephropathy.
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Affiliation(s)
- Ranjan Das
- Dept. of Physiology and Institute of Lifestyle Medicine, Yonsei Univ. Wonju College of Medicine, Ilsan-dong, Wonju, Gangwon-Do 220-701, Republic of Korea.
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828
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Srivastava T, Celsi GE, Sharma M, Dai H, McCarthy ET, Ruiz M, Cudmore PA, Alon US, Sharma R, Savin VA. Fluid flow shear stress over podocytes is increased in the solitary kidney. Nephrol Dial Transplant 2013; 29:65-72. [PMID: 24166460 DOI: 10.1093/ndt/gft387] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
BACKGROUND Glomerular hyperfiltration is emerging as the key risk factor for progression of chronic kidney disease (CKD). Podocytes are exposed to fluid flow shear stress (FFSS) caused by the flow of ultrafiltrate within Bowman's space. The mechanism of hyperfiltration-induced podocyte injury is not clear. We postulated that glomerular hyperfiltration in solitary kidney increases FFSS over podocytes. METHODS Infant Sprague-Dawley rats at 5 days of age and C57BL/6J 14-week-old adult mice underwent unilateral nephrectomy. Micropuncture and morphological studies were then performed on 20- and 60-day-old rats. FFSS over podocytes in uninephrectomized rats and mice was calculated using the recently published equation by Friedrich et al. which includes the variables-single nephron glomerular filtration rate (SNGFR), filtration fraction (f), glomerular tuft diameter (2RT) and width of Bowman's space (s). RESULTS Glomerular hypertrophy was observed in uninephrectomized rats and mice. Uninephrectomized rats on Day 20 showed a 2.0-fold increase in SNGFR, 1.0-fold increase in 2RT and 2.1-fold increase in FFSS, and on Day 60 showed a 1.9-fold increase in SNGFR, 1.3-fold increase in 2RT and 1.5-fold increase in FFSS, at all values of modeled 's'. Similarly, uninephrectomized mice showed a 2- to 3-fold increase in FFSS at all values of modeled SNGFR. CONCLUSIONS FFSS over podocytes is increased in solitary kidneys in both infant rats and adult mice. This increase is a consequence of increased SNGFR. We speculate that increased FFSS caused by reduced nephron number contributes to podocyte injury and promotes the progression of CKD.
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Affiliation(s)
- Tarak Srivastava
- Section of Nephrology, Children's Mercy Hospital and University of Missouri at Kansas City, Kansas City, MO, USA
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829
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Sakamoto K, Ueno T, Kobayashi N, Hara S, Takashima Y, Pastan I, Matsusaka T, Nagata M. The direction and role of phenotypic transition between podocytes and parietal epithelial cells in focal segmental glomerulosclerosis. Am J Physiol Renal Physiol 2013; 306:F98-F104. [PMID: 24154691 DOI: 10.1152/ajprenal.00228.2013] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Focal segmental glomerulosclerosis (FSGS) is a podocyte disease. Among the various histologies of FSGS, active epithelial changes, hyperplasia, as typically seen in the collapsing variant, indicates disease progression. Using a podocyte-specific injury model of FSGS carrying a genetic podocyte tag combined with double immunostaining by different sets of podocytes and parietal epithelial cell (PEC) markers [nestin/Pax8, Wilms' tumor-1 (WT1)/claudin1, and podocalyxin/Pax2], we investigated the direction of epithelial phenotypic transition and its role in FSGS. FSGS mice showed progressive proteinuria and renal dysfunction often accompanied by epithelial hyperplasia, wherein 5-bromo-4-chloro-3-indoyl β-d-galactoside (X-gal)-positive podocyte-tagged cells were markedly decreased. The average numbers of double-positive cells in all sets of markers were significantly increased in the FSGS mice compared with the controls. In addition, the average numbers of double-positive cells for X-gal/Pax8, nestin/Pax8 and podocalyxin/Pax2 staining in the FSGS mice were comparable, whereas those of WT1/claudin1 were significantly increased. When we divided glomeruli from FSGS mice into those with FSGS lesions and those without, double-positive cells tended to be more closely associated with glomeruli without FSGS lesions compared with those with FSGS lesions. Moreover, the majority of double-positive cells appeared to be isolated and very rarely associated with FSGS lesions (1/1,997 glomeruli). This study is the first to show the incidence and localization of epithelial cells with phenotypical changes in FSGS using a genetic tag. The results suggest that the major direction of epithelial phenotypic transition in cellular FSGS is from podocytes to PECs and that these cells were less represented in the active lesions of FSGS.
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Affiliation(s)
- Kazuo Sakamoto
- Kidney and Vascular Pathology, Faculty of Medicine, Univ. of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki, 305-8577, Japan.
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830
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do Nascimento JF, Canani LH, Gerchman F, Rodrigues PG, Joelsons G, dos Santos M, Pereira S, Veronese FV. Messenger RNA levels of podocyte-associated proteins in subjects with different degrees of glucose tolerance with or without nephropathy. BMC Nephrol 2013; 14:214. [PMID: 24103534 PMCID: PMC3853360 DOI: 10.1186/1471-2369-14-214] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 10/04/2013] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND To investigate gene expression of podocyte-specific proteins in urine of diabetes and prediabetes subjects and the association of these proteins with albuminuria. METHODS Fifteen controls, 19 prediabetes, and 67 diabetes subjects were included. Messenger RNA of nephrin, podocin, podocalyxin, synaptopodin, TRPC6, alpha-actinin-4, and TGF-β1 were measured using RT-PCR. Podocyte marker expression was correlated with albuminuria, glycemic control, and renal function. The diagnostic performance of the genes used to detect increased albuminuria was assessed using ROC curves and Poisson regressions. RESULTS Podocyte marker expression was significantly higher in diabetic subjects. Urinary nephrin was correlated with increasing levels of albuminuria; risk of albuminuria increased by 20% for every one-unit increase in the log10 of nephrin mRNA. Nephrinuria was found in 53%, 71%, and 90% of normo-, micro-, and macroalbuminuric diabetes subjects, respectively (p = 0.023). Urinary nephrin, podocalyxin, TRPC6, podocin, and alpha actinin-4 were correlated with glycemic control and albuminuria but not with renal function. CONCLUSIONS Diabetes subjects had higher urinary mRNA levels of podocyte proteins than nondiabetic subjects, even the normoalbuminuric patients. Nephrinuria was correlated with diabetic nephrophathy stage and predicted pathological albuminuria. Urinary mRNA levels of podocyte markers of prediabetic subjects did not differ from controls.
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Affiliation(s)
| | - Luis H Canani
- Division of Endocrinology, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil
| | - Fernando Gerchman
- Division of Endocrinology, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil
| | - Patricia G Rodrigues
- Post Graduate Program in Medicine: Medical Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Gabriel Joelsons
- Post Graduate Program in Medicine: Medical Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Mariane dos Santos
- Post Graduate Program in Medicine: Medical Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Sane Pereira
- Post Graduate Program in Medicine: Medical Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Francisco V Veronese
- Post Graduate Program in Medicine: Medical Sciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
- Division of Nephrology, Hospital de Clínicas de Porto Alegre, Ramiro Barcelos 2350, Porto Alegre, RS ZIP 90035-003, Brazil
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831
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Cheng C, Zheng Z, Shi C, Liu X, Ye Z, Lou T. Advanced glycation end-products reduce podocyte adhesion by activating the renin-angiotensin system and increasing integrin-linked kinase. Exp Ther Med 2013; 6:1494-1498. [PMID: 24255680 PMCID: PMC3829755 DOI: 10.3892/etm.2013.1312] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Accepted: 09/18/2013] [Indexed: 11/29/2022] Open
Abstract
The aim of this study was to investigate the effects of advanced glycation end-products (AGEs) on podocyte adhesion and the underlying mechanisms. Immortalized mouse podocytes were exposed to various conditions and podocyte adhesion was evaluated using a hexosaminidase assay. The expression levels of integrin-linked kinase (ILK) were measured by quantitative polymerase chain reaction (qPCR) and western blotting. Treatment with AGEs resulted in a significant, concentration-dependent reduction in podocyte adhesion (P<0.05) and an incremental rise in ILK expression up to a maximum of 100%. Pretreatment with losartan significantly prevented the upregulation of ILK and attenuated the loss of podocyte adhesion observed in podocytes exposed to AGEs (P<0.05). However, the adhesion of losartan-treated podocytes remained lower than that of the podocytes exposed to bovine serum albumin. The results indicate that AGEs reduce podocyte adhesion via the upregulation of ILK expression, which occurs partly through activation of the renin-angiotensin system in podocytes.
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Affiliation(s)
- Cailian Cheng
- Department of Nephrology, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong 510630, P.R. China
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832
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Abe Y, Sakairi T, Beeson C, Kopp JB. TGF-β1 stimulates mitochondrial oxidative phosphorylation and generation of reactive oxygen species in cultured mouse podocytes, mediated in part by the mTOR pathway. Am J Physiol Renal Physiol 2013; 305:F1477-90. [PMID: 24049142 DOI: 10.1152/ajprenal.00182.2013] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Transforming growth factor (TGF)-β has been associated with podocyte injury; we have examined its effect on podocyte bioenergetics. We studied transformed mouse podocytes, exposed to TGF-β1, using a label-free assay system, Seahorse XF24, which measures oxygen consumption rates (OCR) and extracellular acidification rates (ECAR). Both basal OCR and ATP generation-coupled OCR were significantly higher in podocytes exposed to 0.3-10 ng/ml of TGF-β1 for 24, 48, and 72 h. TGF-β1 (3 ng/ml) increased oxidative capacity 75%, and 96% relative to control after 48 and 72 h, respectively. ATP content was increased 19% and 30% relative to control after a 48- and 72-h exposure, respectively. Under conditions of maximal mitochondrial function, TGF-β1 increased palmitate-driven OCR by 49%. Thus, TGF-β1 increases mitochondrial oxygen consumption and ATP generation in the presence of diverse energy substrates. TGF-β1 did not increase cell number or mitochondrial DNA copy number but did increase mitochondrial membrane potential (MMP), which could explain the OCR increase. Reactive oxygen species (ROS) increased by 32% after TGF-β1 exposure for 48 h. TGF-β activated the mammalian target of rapamycin (mTOR) pathway, and rapamycin reduced the TGF-β1-stimulated increases in OCR, ECAR, ATP generation, cellular metabolic activity, and protein generation. Our data suggest that TGF-β1, acting, in part, via mTOR, increases mitochondrial MMP and OCR, resulting in increased ROS generation and that this may contribute to podocyte injury.
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833
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Isojima T, Harita Y, Furuyama M, Sugawara N, Ishizuka K, Horita S, Kajiho Y, Miura K, Igarashi T, Hattori M, Kitanaka S. LMX1B mutation with residual transcriptional activity as a cause of isolated glomerulopathy. Nephrol Dial Transplant 2013; 29:81-8. [PMID: 24042019 DOI: 10.1093/ndt/gft359] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Nail-patella syndrome (NPS) is a rare autosomal-dominant disorder caused by LMX1B mutation. In patients with the renal lesions typical of NPS without skeletal or nail findings, it is described as nail-patella-like renal disease (NPLRD). However, the pathogenesis of NPLRD is largely unknown. METHODS A 6-year-old girl with microscopic haematuria and mild proteinuria was diagnosed with NPLRD because of an aberrantly thickened glomerular basement membrane (GBM) and deposition of Type III collagen in the GBM observed by electron microscopy. Immunohistological analyses of podocyte protein expression were performed on biopsy tissues. Sequence analysis of LMX1B was performed, and the functional consequences of the detected mutation were analysed by luciferase reporter assay. RESULTS When analysing molecules that are important for podocyte development, maintenance and maturation, CD2AP expression was found to be altered in the podocytes. A novel LMX1B missense mutation (R246Q) was identified. Functional analyses revealed partial but significant impairment of R246Q transcriptional activity. However, no dominant-negative effect of R246Q was detected, which suggests that NPLRD is caused by LMX1B haploinsufficiency. CONCLUSIONS This is the first report on LMX1B mutation identified in a patient with NPLRD. Residual transcriptional activity would account for normality of the nails and patella in this case. Genetic and pathological analyses of additional cases would clarify the role of LMX1B in glomerulopathy without systemic symptoms, which, together with nephropathy in NPS, can be designated as 'LMX1B nephropathy'.
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Affiliation(s)
- Tsuyoshi Isojima
- Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
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834
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Miura K, Kurihara H, Horita S, Chikamoto H, Hattori M, Harita Y, Tsurumi H, Kajiho Y, Sawada Y, Sasaki S, Igarashi T, Kunishima S, Sekine T. Podocyte expression of nonmuscle myosin heavy chain-IIA decreases in idiopathic nephrotic syndrome, especially in focal segmental glomerulosclerosis. Nephrol Dial Transplant 2013; 28:2993-3003. [PMID: 24042022 DOI: 10.1093/ndt/gft350] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Previous studies have identified significant associations between the development of idiopathic focal segmental glomerulosclerosis (FSGS) and MYH9 encoding nonmuscle myosin heavy chain-IIA (NMMHC-IIA). However, these studies focused only on the linkage of MYH9 polymorphisms and development of FSGS. There have been no reports on pathological changes of NMMHC-IIA in human glomerular diseases. Here we report on the precise localization of NMMHC-IIA in podocytes and changes in NMMHC-IIA expression in pathological states in rats and humans. METHODS Immunocytochemical (immunofluorescence and immunoelectron microscopy) studies were performed to determine the precise localization of NMMHC-IIA. Expression levels of NMMHC-IIA were investigated in puromycin aminonucleoside (PAN)-treated rats; and expression levels of NMMHC-IIA and other podocyte-related proteins were investigated in glomeruli of patients with idiopathic FSGS and other heavy proteinuric glomerular diseases. RESULTS NMMHC-IIA was located primarily at the cell body and primary processes of podocytes; this localization is distinct from other podocyte-related molecules causing hereditary FSGS. In PAN-treated rat kidneys, expression levels of NMMHC-IIA in podocytes decreased. Immunohistochemical analysis revealed that expression levels of NMMHC-IIA markedly decreased in idiopathic nephrotic syndrome, especially FSGS, whereas it did not change in other chronic glomerulonephritis showing apparent proteinuria. Changes in NMMHC-IIA expression were observed in glomeruli where expression of nephrin and synaptopodin was maintained. CONCLUSIONS Considering previous genome-wide association studies and development of FSGS in patients with MYH9 mutations, the characteristic localization of NMMHC-IIA and the specific decrease in NMMHC-IIA expression in idiopathic nephrotic syndrome, especially FSGS, suggest the important role of NMMHC-IIA in the development of FSGS.
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Affiliation(s)
- Kenichiro Miura
- Department of Pediatrics, Faculty of Medicine, The University of Tokyo, Tokyo, Japan
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835
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Kim EY, Anderson M, Wilson C, Hagmann H, Benzing T, Dryer SE. NOX2 interacts with podocyte TRPC6 channels and contributes to their activation by diacylglycerol: essential role of podocin in formation of this complex. Am J Physiol Cell Physiol 2013; 305:C960-71. [PMID: 23948707 DOI: 10.1152/ajpcell.00191.2013] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Canonical transient receptor potential-6 (TRPC6) channels have been implicated in the pathophysiology of glomerular diseases. TRPC6 channels are typically activated by diacylglycerol (DAG) during PLC-dependent transduction cascades. TRPC6 channels can also be activated by reactive oxygen species (ROS). We previously showed that podocin is required for DAG analogs to produce robust activation of TRPC6 channels in podocytes. Here we show that endogenous TRPC6 channels in immortalized podocytes reciprocally coimmunoprecipitate with the catalytic subunit of the NADPH oxidase NOX2 (gp91(phox)). The NOX2-TRPC6 interaction was not detected in cells stably expressing a short hairpin RNA targeting podocin, although NOX2 and TRPC6 were present at normal levels. Application of a membrane-permeable DAG analog [1-oleoyl-2-acetyl-sn-glycerol (OAG)] increased generation of ROS in podocytes, but this effect was not detected in podocin knockdown cells. OAG also increased steady-state surface expression of the NOX2 regulatory subunit p47(phox). In whole cell recordings, TRPC6 activation by OAG was reduced in podocytes pretreated with the NOX2 inhibitor apocynin, by the pan-NOX inhibitor diphenylene iodonium, and by tempol, a ROS quencher. Cholesterol depletion and disruption of lipid rafts by methyl-β-cyclodextrin reduced activation of podocyte TRPC6 channels by OAG and also eliminated the NOX2-TRPC6 interaction as assessed by coimmunoprecipitation. These data suggest that active NOX2 assembles with TRPC6 at podocin-organized sterol-rich raft domains and becomes catalytically active in response to DAG. The localized production of ROS contributes to TRPC6 activation by chemical stimuli such as DAG. Podocin appears to be necessary for assembly of the NOX2-TRPC6 complex in lipid rafts.
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Affiliation(s)
- Eun Young Kim
- Department of Biology and Biochemistry, University of Houston, Houston, Texas
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836
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Weidemann F, Sanchez-Niño MD, Politei J, Oliveira JP, Wanner C, Warnock DG, Ortiz A. Fibrosis: a key feature of Fabry disease with potential therapeutic implications. Orphanet J Rare Dis 2013; 8:116. [PMID: 23915644 PMCID: PMC3750297 DOI: 10.1186/1750-1172-8-116] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 08/01/2013] [Indexed: 12/30/2022] Open
Abstract
Fabry disease is a rare X-linked hereditary disease caused by mutations in the AGAL gene encoding the lysosomal enzyme alpha-galactosidase A. Enzyme replacement therapy (ERT) is the current cornerstone of Fabry disease management. Involvement of kidney, heart and the central nervous system shortens life span, and fibrosis of these organs is a hallmark of the disease. Fibrosis was initially thought to result from tissue ischemia secondary to endothelial accumulation of glycosphingolipids in the microvasculature. However, despite ready clearance of endothelial deposits, ERT is less effective in patients who have already developed fibrosis. Several potential explanations of this clinical observation may impact on the future management of Fabry disease. Alternative molecular pathways linking glycosphingolipids and fibrosis may be operative; tissue injury may recruit secondary molecular mediators of fibrosis that are unresponsive to ERT, or fibrosis may represent irreversible tissue injury that limits the therapeutic response to ERT. We provide an overview of Fabry disease, with a focus on the assessment of fibrosis, the clinical consequences of fibrosis, and recent advances in understanding the cellular and molecular mechanisms of fibrosis that may suggest novel therapeutic approaches to Fabry disease.
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Affiliation(s)
- Frank Weidemann
- Department of Medicine, Divisions of Cardiology and Nephrology, The Comprehensive Heart Failure Center at the University of Würzburg, Würzburg, Germany
| | | | - Juan Politei
- Trinity Dupuytren Clinic, Neurology department, Buenos Aires, Argentina
| | | | - Christoph Wanner
- Department of Medicine, Divisions of Cardiology and Nephrology, The Comprehensive Heart Failure Center at the University of Würzburg, Würzburg, Germany
| | | | - Alberto Ortiz
- IIS-Fundacion Jimenez Diaz-UAM, IRSIN/REDINREN, Madrid, Spain
- Unidad de Dialisis, IIS-Fundacion Jimenez Diaz, Av Reyes católicos 2, Madrid, 28040, Spain
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837
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Yasuno K, Kamiie J, Shirota K. Analysis of ultrastructural glomerular basement membrane lesions and podocytes associated with proteinuria and sclerosis in Osborne-Mendel rats with progressive glomerulonephropathy. J Vet Sci 2013; 14:223-6. [PMID: 23814476 PMCID: PMC3694195 DOI: 10.4142/jvs.2013.14.2.223] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Revised: 09/11/2012] [Accepted: 10/23/2012] [Indexed: 11/20/2022] Open
Abstract
The renal glomeruli of 12 male Osborne-Mendel (OM) rats 3 to 24 weeks old were examined by electron microscopy. Effacement of podocyte foot processes (FPs) developed at 3 weeks of age and became progressively worse over time. Loss or dislocation of the slit membrane was also found. Vacuoles and osmiophilic lysosomes appeared in the podocytes starting at 6 weeks of age. Podocyte detachment from the glomerular basement membrane (GBM) was apparent at 18 weeks of age. Laminated GBM was occasionally observed in all animals. These features might lead to the development of spontaneous proteinuria and glomerulosclerosis in OM rats.
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Affiliation(s)
- Kyohei Yasuno
- Research Institute of Biosciences, School of Veterinary Medicine, Azabu University, Kanagawa 252-5201, Japan
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838
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Shen L, Lu G, Dong N, Ma Z, Ruan C. Simvastatin increases ADAMTS13 expression in podocytes. Thromb Res 2013; 132:94-9. [PMID: 23816135 DOI: 10.1016/j.thromres.2013.05.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Revised: 03/30/2013] [Accepted: 05/07/2013] [Indexed: 02/08/2023]
Abstract
INTRODUCTION ADAMTS13 is a specific von Willebrand factor-cleaving protease. Severe deficiency of ADAMTS13 is the main cause of thrombotic thrombocytopenic purpura. ADAMTS13 is mainly synthesized and released from hepatic stellate cells and endothelial cells, but is also expressed in other cells, including kidney podocytes. Simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, has a beneficial effect on atherosclerosis and also has anti-inflammatory and antithrombotic properties. A recent study indicates that ADAMTS13 reduces inflammatory plaque formation during early atherosclerosis in mice. In our study, we investigated the effects of simvastatin on inflammatory cytokines-induced ADAMTS13 expression in podocytes. MATERIALS AND METHODS A conditionally immortalized mouse podocyte cell line was utilized to study the expression of ADAMTS13 in podocytes. The influence of TNF-α, IL-4, IL-6 and simvastatin on ADAMTS13 was investigated. ADAMTS13 mRNA levels in podocytes were measured by using real-time PCR and protein levels were detected by Western blotting. RESULTS Simvastatin significantly up-regulated the expression levels of ADAMTS13 mRNA and protein in podocytes. IL-6 decreased ADAMTS13 expression, and TNF-α had no significant effects on ADAMTS13 expression in podocytes. IL-4 reduced ADAMTS13 mRNA expression but not its protein level. Simvastatin was able also reversed the inhibitory effect of IL-6. CONCLUSIONS We demonstrate that simvastatin increases the expression of ADAMTS13 in a dose-dependent manner in podocytes, which likely contributes to the antithrombotic property of statin. Different inflammatory cytokines have different effects on the levels of ADAMTS13 mRNA expression and protein within podocytes.
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Affiliation(s)
- Lei Shen
- Department of Nephrology, The First Affiliated Hospital of Soochow University, Suzhou 215006, Jiangsu, China
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839
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Bi J, Chase SE, Pellenz CD, Kurihara H, Fanning AS, Krendel M. Myosin 1e is a component of the glomerular slit diaphragm complex that regulates actin reorganization during cell-cell contact formation in podocytes. Am J Physiol Renal Physiol 2013; 305:F532-44. [PMID: 23761676 DOI: 10.1152/ajprenal.00223.2013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Glomerular visceral epithelial cells, also known as podocytes, are critical to both normal kidney function and the development of kidney disease. Podocyte actin cytoskeleton and their highly specialized cell-cell junctions (also called slit diaphragm complexes) play key roles in controlling glomerular filtration. Myosin 1e (myo1e) is an actin-based molecular motor that is expressed in renal glomeruli. Disruption of the Myo1e gene in mice and humans promotes podocyte injury and results in the loss of the integrity of the glomerular filtration barrier. Here, we have used biochemical and microscopic approaches to determine whether myo1e is associated with the slit diaphragm complexes in glomerular podocytes. Myo1e was consistently enriched in the slit diaphragm fraction during subcellular fractionation of renal glomeruli and colocalized with the slit diaphragm markers in mouse kidney. Live cell imaging studies showed that myo1e was recruited to the newly formed cell-cell junctions in cultured podocytes, where it colocalized with the actin filament cables aligned with the nascent contacts. Myo1e-null podocytes expressing FSGS-associated myo1e mutant (A159P) did not efficiently assemble actin cables along new cell-cell junctions. We have mapped domains in myo1e that were critical for its localization to cell-cell junctions and determined that the SH3 domain of myo1e tail interacts with ZO-1, a component of the slit diaphragm complex and tight junctions. These findings suggest that myo1e represents a component of the slit diaphragm complex and may contribute to regulating junctional integrity in kidney podocytes.
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Affiliation(s)
- J Bi
- Dept. of Cell and Developmental Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13210.
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840
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Shimoi A, Hatakeyama H, Miyoshi S, Watanabe M. Unchanged distribution density of anionic sites on the glomerular wall in rats with active heymann nephritis. J Toxicol Pathol 2013; 26:11-7. [PMID: 23723563 PMCID: PMC3620209 DOI: 10.1293/tox.26.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Accepted: 10/09/2012] [Indexed: 11/22/2022] Open
Abstract
In various kinds of glomerulonephritis, alteration of anionic charge on the glomerular basement membrane (GBM) and podocytes has been controversial for more than decade. To elucidate the relation between glomerular protein leakage and anionic sites on the glomerular wall, we examined the distribution of anionic sites on the GBM and podocytes of rats with active Heymann nephritis (AHN). Urinalysis for protein levels was conducted, and the kidneys were examined using electron microscopic cytochemistry for the assessment of anionic charge with two cationic probes. The anionic sites on podocytes were decreased in number in the AHN rats; however, the distributions of anionic sites on the GBM were similar in density to those seen in the control animals. From these results, we consider that the decrease in anionic charge density on podocytes might be attributable to protein leakage and that the charge barrier of the GBM is irrelevant to the protein leakage in AHN rats.
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Affiliation(s)
- Akihito Shimoi
- Ina Research Inc., 2148-188 Nishiminowa, Ina, Nagano 399-4501, Japan
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841
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Hale LJ, Hurcombe J, Lay A, Santamaría B, Valverde AM, Saleem MA, Mathieson PW, Welsh GI, Coward RJ. Insulin directly stimulates VEGF-A production in the glomerular podocyte. Am J Physiol Renal Physiol 2013; 305:F182-8. [PMID: 23698113 DOI: 10.1152/ajprenal.00548.2012] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Podocytes are critically important for maintaining the integrity of the glomerular filtration barrier and preventing albuminuria. Recently, it has become clear that to achieve this, they need to be insulin sensitive and produce an optimal amount of VEGF-A. In other tissues, insulin has been shown to regulate VEGF-A release, but this has not been previously examined in the podocyte. Using in vitro and in vivo approaches, in the present study, we now show that insulin regulates VEGF-A in the podocyte in both mice and humans via the insulin receptor (IR). Insulin directly increased VEGF-A mRNA levels and protein production in conditionally immortalized wild-type human and murine podocytes. Furthermore, when podocytes were rendered insulin resistant in vitro (using stable short hairpin RNA knockdown of the IR) or in vivo (using transgenic podocyte-specific IR knockout mice), podocyte VEGF-A production was impaired. Importantly, in vivo, this occurs before the development of any podocyte damage due to podocyte insulin resistance. Modulation of VEGF-A by insulin in the podocyte may be another important factor in the development of glomerular disease associated with conditions in which insulin signaling to the podocyte is deranged.
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Affiliation(s)
- L J Hale
- Academic and Children's Renal Unit, University of Bristol, Learning and Research building, Southmead Hospital, Bristol, United Kingdom
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842
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Anderson M, Kim EY, Hagmann H, Benzing T, Dryer SE. Opposing effects of podocin on the gating of podocyte TRPC6 channels evoked by membrane stretch or diacylglycerol. Am J Physiol Cell Physiol 2013; 305:C276-89. [PMID: 23657570 DOI: 10.1152/ajpcell.00095.2013] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Gain-of-function mutations in the transient receptor potential (TRP) cation channel subfamily C member 6 (TRPC6) gene and mutations in the NPHS2 gene encoding podocin result in nephrotic syndromes. The purpose of this study was to determine the functional significance of biochemical interactions between these proteins. We observed that gating of TRPC6 channels in podocytes is markedly mechanosensitive and can be activated by hyposmotic stretch or indentation of the plasma membrane. Stretch activation of cationic currents was blocked by small interfering RNA knockdown of TRPC6, as well as by SKF-96365 or micromolar La(3+). Stretch activation of podocyte TRPC6 persisted in the presence of inhibitors of phospholipase C (U-73122) and phospholipase A2 (ONO-RS-082). Robust stretch responses also persisted when recording electrodes contained guanosine 5'-O-(2-thiodiphosphate) at concentrations that completely suppressed responses to ANG II. Stretch responses were enhanced by cytochalasin D but were abolished by the peptide GsMTx4, suggesting that forces are transmitted to the channels through the plasma membrane. Podocin and TRPC6 interact at their respective COOH termini. Knockdown of podocin markedly increased stretch-evoked activation of TRPC6 but nearly abolished TRPC6 activation evoked by a diacylglycerol analog. These data suggest that podocin acts as a switch to determine the preferred mode of TRPC6 activation. They also suggest that podocin deficiencies will result in Ca(2+) overload in foot processes, as with gain-of-function mutations in the TRPC6 gene. Finally, they suggest that mechanical activation of TRP family channels and the preferred mode of TRP channel activation may depend on whether members of the stomatin/prohibitin family of hairpin loop proteins are present.
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Affiliation(s)
- Marc Anderson
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA
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843
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Bechtel W, Helmstädter M, Balica J, Hartleben B, Schell C, Huber TB. The class III phosphatidylinositol 3-kinase PIK3C3/VPS34 regulates endocytosis and autophagosome-autolysosome formation in podocytes. Autophagy 2013; 9:1097-9. [PMID: 23614954 DOI: 10.4161/auto.24634] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Phosphatidylinositol phosphates are key regulators of vesicle identity, formation and trafficking. In mammalian cells, the evolutionarily conserved class III PtdIns 3-kinase PIK3C3/VPS34 is part of a large multiprotein complex that catalyzes the localized phosphorylation of phosphatidylinositol to phosphatidylinositol-3-phosphate (PtdIns3P). We demonstrate that PIK3C3 has a key function in vesicular trafficking, endocytosis and autophagosome-autolysosome formation in the highly specialized glomerular podocytes.
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Affiliation(s)
- Wibke Bechtel
- Renal Division; University Hospital Freiburg; Freiburg, Germany
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844
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Yasuno K, Araki S, Sakashita H, Kobayashi R, Baba T, Kawakami H, Kamiie J, Ogihara K, Shirota K. Development of podocyte injuries in Osborne-Mendel rats is accompanied by reduced expression of podocyte proteins. J Comp Pathol 2013; 149:280-90. [PMID: 23582971 DOI: 10.1016/j.jcpa.2013.01.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Revised: 12/12/2012] [Accepted: 01/25/2013] [Indexed: 11/22/2022]
Abstract
Osborne-Mendel (OM) rats spontaneously develop glomerulopathy with progressive podocyte injury. Changes in protein expression levels in the foot processes of podocytes have been suggested to play an important role in the development of renal disease. The aim of this study was to investigate the temporal relationship between the expression of five podocyte proteins (nephrin, podocin, synaptopodin, α-actinin-4 and α3-integrin) and the development of podocyte injuries, proteinuria and glomerulosclerosis in OM rats. Male OM rats 5-20 weeks of age and age-matched Fischer 344 rats were used. Semiquantitative analysis of expression of the five podocyte proteins was performed by immunofluorescence labelling. Nephrin mRNA expression was determined by quantitative real-time reverse transcriptase polymerase chain reaction and nephrin protein expression was determined by mass spectrometry. Progressive reduction in expression of the podocyte proteins correlated with the progression of podocyte injuries, the development of proteinuria and the subsequent development of glomerulosclerosis. Nephrin mRNA expression and nephrin concentration also showed temporal decreases in OM rats. Altered expression of podocyte proteins preceded the development of proteinuria and glomerulosclerosis, suggesting that this event contributes to podocyte dysfunction and progression to glomerulosclerosis.
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845
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Schordan S, Grisk O, Schordan E, Miehe B, Rumpel E, Endlich K, Giebel J, Endlich N. OPN deficiency results in severe glomerulosclerosis in uninephrectomized mice. Am J Physiol Renal Physiol 2013; 304:F1458-70. [PMID: 23552865 DOI: 10.1152/ajprenal.00615.2012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Osteopontin (OPN) expression has been reported to be elevated in experimental models of renal injury such as arterial hypertension or diabetic nephropathy finally leading to focal segmental glomerulosclerosis (FSGS). FSGS is characterized by glomerular matrix deposition and loss or damage of podocytes that represent the main constituents of the glomerular filtration barrier. To evaluate the role of OPN in the kidney we investigated WT and OPN knockout mice (OPN-/-) without treatment, after uninephrectomy (UNX), as well as after UNX and desoxycorticosterone acetate (DOCA)-salt treatment with respect to urine parameters, glomerular morphology, and expression of podocyte markers. OPN-/- mice showed normal urine parameters while a thickening of the glomerular basement membrane was evident. Intriguingly, following UNX, OPN-/- mice exhibited prominent FSGS, proteinuria, and glomerular matrix deposition. Electron microscopy revealed bulgings of the glomerular basement membrane and occasionally an effacement of podocytes. After UNX and DOCA-salt treatment, severe glomerular lesions as well as proteinuria and albuminuria were seen in WT and OPN-/- mice. Moreover, we found a reduction of specific markers such as Wilm's tumor-1, podocin, and synaptopodin in both experimental groups indicating a loss of podocytes. Podocyte damage was accompanied by increased number of Ki-67-positive cells in the parietal epithelium of Bowman's capsule. We conclude that OPN plays a crucial role in adaptation of podocytes following renal ablation and is renoprotective when glomerular mechanical load is increased.
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Affiliation(s)
- Sandra Schordan
- Department of Anatomy and Cell Biology, Universitätsmedizin Greifswald, Greifswald, Germany
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846
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Chandel N, Sharma B, Husain M, Salhan D, Singh T, Rai P, Mathieson PW, Saleem MA, Malhotra A, Singhal PC. HIV compromises integrity of the podocyte actin cytoskeleton through downregulation of the vitamin D receptor. Am J Physiol Renal Physiol 2013; 304:F1347-57. [PMID: 23467424 DOI: 10.1152/ajprenal.00717.2012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Alterations in the podocyte actin cytoskeleton have been implicated in the development of proteinuric kidney diseases. In the present study, we evaluated the effect of HIV on the podocyte actin cytoskeleton and the mechanism involved. We hypothesized that HIV may be compromising the actin cytoskeleton via downregulation of the vitamin D receptor (VDR) of conditionally immortalized differentiated human podocytes (CIDHPs). HIV-transduced podocytes (HIV/CIDHPs) not only displayed downregulation of VDR but also showed activation of the renin-angiotensin system (RAS) in the form of enhanced expression of renin and increased production of ANG II. Moreover, CIDHPs lacking VDR displayed enhanced ANG II production, and treatment of HIV/CIDHPs with EB1089 (vitamin D3; VD) attenuated ANG II production. HIV/CIDHPs as well as ANG II-treated CIDHPs exhibited enhanced expression of cathepsin (CTS) L. Additionally, losartan (an ANG II type I receptor blocker) inhibited both HIV- and ANG II-induced podocyte cathepsin L expression. Furthermore, VD downregulated HIV-induced podocyte CTSL expression. Both losartan and free radical scavengers attenuated HIV- and ANG II-induced podocyte reactive oxygen species (ROS) generation. HIV also led to cytosolic CTSL accumulation through enhancement of podocyte lysosomal membrane permeabilization; on the other hand, VD, losartan, and superoxide dismutase (SOD) attenuated HIV-induced enhanced podocyte cytosolic CTSL accumulation. Morphological evaluation of HIV/CIDHPs revealed sparse actin filaments and attenuated expression of dynamin. Interestingly, podocytes lacking CTSL displayed enhanced dynamin expression, and HIV/CIDHPs expressing CTSL exhibited downregulation of dynamin. These findings indicate that HIV-induced downregulation of podocyte VDR and associated RAS activation and cytosolic CTSL accumulation compromised the actin cytoskeleton.
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Affiliation(s)
- Nirupama Chandel
- Department of Medicine and Immunology Center, Feinstein Institute for Medical Research, North Shore-Long Island Jewish Health System, Manhasset, NY, USA
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847
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Hofstra JM, Lainez S, van Kuijk WHM, Schoots J, Baltissen MPA, Hoefsloot LH, Knoers NVAM, Berden JHM, Bindels RJM, van der Vlag J, Hoenderop JGJ, Wetzels JFM, Nijenhuis T. New TRPC6 gain-of-function mutation in a non-consanguineous Dutch family with late-onset focal segmental glomerulosclerosis. Nephrol Dial Transplant 2013; 28:1830-8. [PMID: 23291369 DOI: 10.1093/ndt/gfs572] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Focal segmental glomerulosclerosis (FSGS) is a leading cause of steroid-resistant nephrotic syndrome. Hereditary FSGS is frequently caused by mutations in important structural podocyte proteins, including the slit diaphragm-associated transient receptor potential channel C6 (TRPC6). METHODS In five patients with biopsy-proven autosomal-dominant FSGS from five different Dutch families, all 13 exons of TRPC6 were sequenced. Upon identification of a novel TRPC6 sequence variant, the resultant amino acid change was introduced in the wild-type TRPC6 protein and functionally tested using patch-clamp analyses and cell-surface biotinylation experiments. RESULTS None of the previously described TRPC6 mutations were found in our cohort. In one family, we identified a novel c.524G>A sequence variant resulting in a p.Arg175Gln (R175Q) substitution in the TRPC6 protein. This sequence variant was absent in 449 control subjects and from public SNP databases. The mutation was located in the third ankyrin repeat domain (ANK3) in the cytoplasmic N-tail of TRPC6, important for protein-protein interaction and regulation of ion channel activity. Patch-clamp analyses of the mutant channel indeed showed an increased TRPC6 channel-mediated current. However, cell-surface expression of the mutant channel was not increased. CONCLUSIONS We identified a novel TRPC6 p.Arg175Gln gain-of-function mutation that shows increased TRPC6-mediated current, which is not due to altered cell-surface expression. This is the first mutation identified in ANK3 of the TRPC6 N-tail and is most likely responsible for the late-onset autosomal dominant FSGS in this family.
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Affiliation(s)
- Julia M Hofstra
- Department of Nephrology, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
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848
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Abstract
Podocytes are highly specialized epithelial cells localized in the kidney glomerulus. The distinct cell signaling events and unique cytoskeletal architecture tailor podocytes to withstand changes in hydrostatic pressure during glomerular filtration. Alteration of glomerular filtration leads to kidney disease and frequently manifests with proteinuria. It has been increasingly recognized that cell signaling and cytoskeletal dynamics are coupled more tightly to membrane trafficking than previously thought. Membrane trafficking coordinates the cross-talk between protein networks and signaling cascades in a spatially and temporally organized fashion and may be viewed as a communication highway between the cell exterior and interior. Membrane trafficking involves transport of cargo from the plasma membrane to the cell interior (i.e., endocytosis) followed by cargo trafficking to lysosomes for degradation or to the plasma membrane for recycling. Yet, recent studies indicate that the conventional classification does not fully reflect the complex and versatile nature of membrane trafficking. While the increasing complexity of elaborate protein scaffolds and signaling cascades is being recognized in podocytes, the role of membrane trafficking is less well understood. This review will focus on the role of membrane trafficking in podocyte health and disease.
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849
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Fang L, Radovits T, Szabó G, Mózes MM, Rosivall L, Kökény G. Selective phosphodiesterase-5 (PDE-5) inhibitor vardenafil ameliorates renal damage in type 1 diabetic rats by restoring cyclic 3',5' guanosine monophosphate (cGMP) level in podocytes. Nephrol Dial Transplant 2012. [PMID: 23203993 DOI: 10.1093/ndt/gfs391] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Diabetic nephropathy (DN) is characterized by podocyte damage and increased phosphodiesterase-5 (PDE-5) activity-exacerbating nitric oxide (NO)-cyclic 3',5' guanosine monophosphate (cGMP) pathway dysfunction. It has been shown that PDE-5 inhibition ameliorates DN. The role of podocytes in this mechanism remains unclear. We investigated how selective PDE-5 inhibition influences podocyte damage in streptozotocin (STZ) diabetic rats. METHODS Male Sprague-Dawley rats (250-300 g) were injected with STZ and divided into two groups: (i) STZ control (non-treated, STZ, n=6) and (ii) STZ+vardenafil treatment (10 mg/kg/day, STZ-Vard, n=8). Non-diabetic rats served as negative controls (Control, n=7). Following 8 weeks of treatment, immunohistochemical and molecular analysis of the kidneys were performed. RESULTS Diabetic rats had proteinuria, increased renal transforming growth factor (TGF)-β1 expression and podocyte damage when compared with controls. Vardenafil treatment resulted in preserved podocyte cGMP levels, less proteinuria, reduced renal TGF-β1 expression, desmin immunostaining in podocytes and restored both nephrin and podocin mRNA expression. Diabetes led to increased glomerular nitrotyrosine formation and renal neuronal nitric oxide synthase and endothelial nitric oxide synthase mRNA expression, but vardenafil did not influence these parameters. CONCLUSIONS Our data suggest that a dysfunctional NO-cGMP pathway exacerbates podocyte damage in diabetes. In conclusion, vardenafil treatment preserves podocyte function and reduces glomerular damage, which indicates therapeutic potential in patients with DN.
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Affiliation(s)
- Lilla Fang
- Institute of Pathophysiology, Semmelweis University, Budapest, Hungary
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850
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Kodama F, Asanuma K, Takagi M, Hidaka T, Asanuma E, Fukuda H, Seki T, Takeda Y, Hosoe-Nagai Y, Asao R, Horikoshi S, Tomino Y. Translocation of dendrin to the podocyte nucleus in acute glomerular injury in patients with IgA nephropathy. Nephrol Dial Transplant 2012; 28:1762-72. [PMID: 23143340 DOI: 10.1093/ndt/gfs500] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND It has been reported that podocytopenia has been occurring with increasing disease severity in patients with IgA nephropathy (IgAN). Dendrin is localized at the slit diaphragm (SD) in podocytes. We showed that dendrin translocates to the nucleus of injured podocytes in experimental nephritis and the nuclear dendrin promotes podocyte apoptosis. It is still unknown whether dendrin translocates from the SD to podocyte nucleus in IgAN. We investigated the presence of nuclear dendrin in patients with IgAN and the association between the translocated dendrin to the podocyte nucleus and disease activity. METHODS Fourteen adult patients with IgAN were enrolled. The pathological parameters were analyzed. Immunostaining of renal biopsy specimens and urinary sediments from IgAN or minimal change nephrotic syndrome (MCNS) as the control was performed. RESULTS A positive correlation was observed between an acute extracapillary change and the number of dendrin-positive nuclei. The location of dendrin in the nuclei was found in urinary podocytes of IgAN. The number of dendrin-positive nuclei in urinary podocytes of IgAN was significantly higher than that of MCNS. Urinary podocytes, which expressed the apoptosis marker annexin V, were also detected in IgAN. The translocation of dendrin to the podocyte nucleus as well as strong cathepsin L staining were detected in the glomeruli of IgAN. CONCLUSION An increasing number of dendrin-positive nuclei in the glomeruli suggest acute glomerular injury in IgAN. Apoptotic podocytes were detectable in the urine of IgAN. It appears that the translocation of dendrin to the podocyte nuclei enhances podocyte apoptosis in acute glomerular injury and leads to podocytopenia in patients with IgAN.
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Affiliation(s)
- Fumiko Kodama
- Division of Nephrology, Department of Internal Medicine, Juntendo University Faculty of Medicine, Tokyo, Japan
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