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Telang AC, Ference-Salo JT, McElliott MC, Chowdhury M, Beamish JA. Sustained alterations in proximal tubule gene expression in primary culture associate with HNF4A loss. Sci Rep 2024; 14:22927. [PMID: 39358473 PMCID: PMC11447228 DOI: 10.1038/s41598-024-73861-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Accepted: 09/22/2024] [Indexed: 10/04/2024] Open
Abstract
Primary cultures of proximal tubule cells are widely used to model the behavior of kidney epithelial cells in vitro. However, de-differentiation of primary cells upon culture has been observed and appreciated for decades, yet the mechanisms driving this phenomenon remain poorly understood. This confounds the interpretation of experiments using primary kidney epithelial cells and prevents their use to engineer functional kidney tissue ex vivo. In this report, we measure the dynamics of cell-state transformations in early primary culture of mouse proximal tubules to identify key pathways and processes that correlate with and may drive de-differentiation. Our data show that the loss of proximal-tubule-specific genes is rapid, uniform, and sustained even after confluent, polarized epithelial monolayers develop. This de-differentiation occurs uniformly across many common culture condition variations. Changes in early culture were strongly associated with the loss of HNF4A. Exogenous re-expression of HNF4A can promote expression of a subset of proximal tubule genes in a de-differentiated proximal tubule cell line. Using genetically labeled proximal tubule cells, we show that selective pressures very early in culture influence which cells grow to confluence. Together, these data indicate that the loss of in vivo function in proximal tubule cultures occurs very early and suggest that the sustained loss of HNF4A is a key regulatory event mediating this change.
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Affiliation(s)
- Asha C Telang
- Division of Nephrology, Department of Internal Medicine, University of Michigan, 1500 E. Medical Center Drive, SPC 5364, Ann Arbor, MI, 48109, USA
| | - Jenna T Ference-Salo
- Division of Nephrology, Department of Internal Medicine, University of Michigan, 1500 E. Medical Center Drive, SPC 5364, Ann Arbor, MI, 48109, USA
| | - Madison C McElliott
- Division of Nephrology, Department of Internal Medicine, University of Michigan, 1500 E. Medical Center Drive, SPC 5364, Ann Arbor, MI, 48109, USA
| | - Mahboob Chowdhury
- Division of Nephrology, Department of Internal Medicine, University of Michigan, 1500 E. Medical Center Drive, SPC 5364, Ann Arbor, MI, 48109, USA
| | - Jeffrey A Beamish
- Division of Nephrology, Department of Internal Medicine, University of Michigan, 1500 E. Medical Center Drive, SPC 5364, Ann Arbor, MI, 48109, USA.
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Saad S, Zhang J, Yong R, Yaghobian D, Wong MG, Kelly DJ, Chen XM, Pollock CA. Role of the EGF receptor in PPARγ-mediated sodium and water transport in human proximal tubule cells. Diabetologia 2013; 56:1174-82. [PMID: 23370527 DOI: 10.1007/s00125-013-2835-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2012] [Accepted: 01/04/2013] [Indexed: 01/17/2023]
Abstract
AIM/HYPOTHESIS This study aimed to determine the interaction between the EGF receptor (EGFR) and peroxisome proliferator-activated receptor γ (PPARγ) and the role of EGFR in sodium and water transport in the proximal tubule. METHODS Primary human proximal tubule cells (PTCs) were exposed to high glucose in the presence and absence of pioglitazone. Total and phospho-EGFR levels and EGFR mRNA expression were determined by western blot and real-time PCR, respectively. Sodium-hydrogen exchanger-3 (NHE3), PPARγ and aquaporin 1 (AQP1) levels were determined by western blot. The role of EGFR was elucidated using the EGFR tyrosine kinase inhibitor, PKI166. The role of PPARγ in high-glucose conditions was determined using specific PPARγ small interfering (si)RNA. P-EGFR, PPARγ, AQP1 and NHE3 production in a rat model of diabetes (streptozotocin-induced hypertensive Ren-2 transgenic [mRen2]27 rats) and controls, with or without pioglitazone treatment, was determined by immunohistochemistry. The PPARγ and EGFR interaction was determined by chromatin immunoprecipitation assay, and the effect of pioglitazone on EGFR activation by luciferase assay. RESULTS PTCs exposed to both high glucose and pioglitazone increased protein abundance of P-EGFR, NHE3, AQP1 and PPARγ. Pioglitazone-induced upregulation of NHE3 and AQP1 was abolished by PKI166. High-glucose-induced increases in P-EGFR, NHE3 and AQP1 were decreased with PPARγ siRNA. AQP1 and NHE3 but not PPARγ were increased in a diabetic rat model and further increased by pioglitazone treatment. Pioglitazone induced PPARγ binding to the EGFR promoter and subsequent downstream activation. CONCLUSIONS/INTERPRETATION Our data suggest that EGFR activation mediates PPARγ-induced sodium and water reabsorption via upregulation of NHE3 and AQP1 channels in the proximal tubule. EGFR inhibition may be a therapeutic strategy in the treatment of diabetic nephropathy and in limiting salt and water retention, which currently restricts the use of PPARγ agonists.
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Affiliation(s)
- S Saad
- Renal Research Laboratories, Kolling Institute of Medical Research, Royal North Shore Hospital, Kolling Building, St Leonards, NSW 2065, Australia.
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Yesudas R, Snyder R, Abbruscato T, Thekkumkara T. Functional role of sodium glucose transporter in high glucose-mediated angiotensin type 1 receptor downregulation in human proximal tubule cells. Am J Physiol Renal Physiol 2012; 303:F766-74. [PMID: 22647632 DOI: 10.1152/ajprenal.00651.2011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previously, we have demonstrated human angiotensin type 1 receptor (hAT(1)R) promoter architecture with regard to the effect of high glucose (25 mM)-mediated transcriptional repression in human proximal tubule epithelial cells (hPTEC; Thomas BE, Thekkumkara TJ. Mol Biol Cell 15: 4347-4355, 2004). In the present study, we investigated the role of glucose transporters in high glucose-mediated hAT(1)R repression in primary hPTEC. Cells were exposed to normal glucose (5.5 mM) and high glucose (25 mM), followed by determination of hyperglycemia-mediated changes in receptor expression and glucose transporter activity. Exposure of cells to high glucose resulted in downregulation of ANG II binding (4,034 ± 163.3 to 1,360 ± 154.3 dpm/mg protein) and hAT(1)R mRNA expression (reduced 60.6 ± 4.643%) at 48 h. Under similar conditions, we observed a significant increase in glucose uptake (influx) in cells exposed to hyperglycemia. Our data indicated that the magnitude of glucose influx is concentration and time dependent. In euglycemic cells, inhibiting sodium-glucose cotransporters (SGLTs) with phlorizin and facilitative glucose transporters (GLUTs) with phloretin decreased glucose influx by 28.57 ± 0.9123 and 54.33 ± 1.202%, respectively. However, inhibiting SGLTs in cells under hyperglycemic conditions decreased glucose influx by 53.67 ± 2.906%, while GLUT-mediated glucose uptake remained unaltered (57.67 ± 3.180%). Furthermore, pretreating cells with an SGLT inhibitor reversed high glucose-mediated downregulation of the hAT(1)R, suggesting an involvement of SGLT in high glucose-mediated hAT(1)R repression. Our results suggest that in hPTEC, hyperglycemia-induced hAT(1)R downregulation is largely mediated through SGLT-dependent glucose influx. As ANG II is an important modulator of hPTEC transcellular sodium reabsorption and function, glucose-mediated changes in hAT(1)R gene expression may participate in the pathogenesis of diabetic renal disease.
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Affiliation(s)
- Rekha Yesudas
- Department of Biomedical Sciences, Texas Tech University Health Sciences Center,1300 Coulter Dr., Amarillo, TX 79106, USA
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Valente MJ, Henrique R, Costa VL, Jerónimo C, Carvalho F, Bastos ML, de Pinho PG, Carvalho M. A rapid and simple procedure for the establishment of human normal and cancer renal primary cell cultures from surgical specimens. PLoS One 2011; 6:e19337. [PMID: 21573239 PMCID: PMC3087760 DOI: 10.1371/journal.pone.0019337] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Accepted: 03/28/2011] [Indexed: 01/31/2023] Open
Abstract
The kidney is a target organ for the toxicity of several xenobiotics and is also highly susceptible to the development of malignant tumors. In both cases, in vitro studies provide insight to cellular damage, and represent adequate models to study either the mechanisms underlying the toxic effects of several nephrotoxicants or therapeutic approaches in renal cancer. The development of efficient methods for the establishment of human normal and tumor renal cell models is hence crucial. In this study, a technically simple and rapid protocol for the isolation and culture of human proximal tubular epithelial cells and human renal tumor cells from surgical specimens is presented. Tumor and normal tissues were processed by using the same methodology, based on mechanical disaggregation of tissue followed by enzymatic digestion and cell purification by sequential sieving. The overall procedure takes roughly one hour. The resulting cell preparations have excellent viabilities and yield. Establishment of primary cultures from all specimens was achieved successfully. The origin of primary cultured cells was established through morphological evaluation. Normal cells purity was confirmed by immunofluorescent staining and reverse transcription-polymerase chain reaction analysis for expression of specific markers.
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Affiliation(s)
- Maria João Valente
- REQUIMTE - Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal
- * E-mail: (MJV); (MC)
| | - Rui Henrique
- Department of Pathology, Portuguese Oncology Institute-Porto, Porto, Portugal
- Department of Pathology and Molecular Immunology, Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal
- Cancer Epigenetics Group – Research Center, Portuguese Oncology Institute-Porto, Porto, Portugal
| | - Vera L. Costa
- Cancer Epigenetics Group – Research Center, Portuguese Oncology Institute-Porto, Porto, Portugal
| | - Carmen Jerónimo
- Department of Pathology and Molecular Immunology, Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal
- Cancer Epigenetics Group – Research Center, Portuguese Oncology Institute-Porto, Porto, Portugal
| | - Félix Carvalho
- REQUIMTE - Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal
| | - Maria L. Bastos
- REQUIMTE - Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal
| | - Paula Guedes de Pinho
- REQUIMTE - Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal
| | - Márcia Carvalho
- REQUIMTE - Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal
- Faculty of Health Sciences, University Fernando Pessoa, Porto, Portugal
- * E-mail: (MJV); (MC)
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Vesey DA, Qi W, Chen X, Pollock CA, Johnson DW. Isolation and primary culture of human proximal tubule cells. Methods Mol Biol 2009; 466:19-24. [PMID: 19148604 DOI: 10.1007/978-1-59745-352-3_2] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Primary cultures of renal proximal tubule cells (PTC) have been widely used to investigate tubule cell function. They provide a model system where confounding influences of renal haemodynamics, cell heterogeneity, and neural activity are eliminated. Additionally they are likely to more closely resemble PTC in vivo than established kidney cell lines, which are often virally immortalised and are of uncertain origin. This chapter describes a method used in our laboratories to isolate and culture pure populations of human PTC. The cortex is dissected away from the medulla and minced finely. Following collagenase digestion, the cells are passed through a sieve and separated on a Percoll density gradient. An almost pure population of tubule fragments form a band at the base of the gradient. Cultured in a hormonally defined serum-free growth media, they form a tightly packed monolayer that retains the differentiated characteristics of PTC for up to three passages.
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Affiliation(s)
- David A Vesey
- Centre for Kidney Disease Research, Department of Medicine, University of Queensland, Princess Alexandra Hospital, Woolloongabba, Queensland, Australia
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Vesey DA, Kruger WA, Poronnik P, Gobé GC, Johnson DW. Proinflammatory and proliferative responses of human proximal tubule cells to PAR-2 activation. Am J Physiol Renal Physiol 2007; 293:F1441-9. [PMID: 17699557 DOI: 10.1152/ajprenal.00088.2007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Despite the abundant expression of protease-activated receptor (PAR)-2 in the kidney, its relevance to renal physiology is not well understood. A role for this receptor in inflammation and cell proliferation has recently been suggested in nonrenal tissues. The aims of this study were to demonstrate that human proximal tubule cells (PTC) express functional PAR-2 and to investigate whether its activation can mediate proinflammatory and proliferative responses in these cells. Primary human PTC were cultured under serum-free conditions with or without the PAR-2-activating peptide SLIGKV-NH2 (up to 800 microM), a control peptide, VKGILS-NH2 (200 microM), or trypsin (0.01-100 nM). PAR-2 expression (RT-PCR), intracellular Ca2+ mobilization (fura-2 fluorimetry), DNA synthesis (thymidine incorporation), fibronectin production (ELISA, Western blotting), and monocyte chemotactic protein (MCP)-1 secretion (ELISA) were measured. Trypsinogen expression in kidney and PTC cultures was determined by immunohistochemistry and Western blotting. In the kidney PTC were the predominant cell type expressing PAR-2. SLIGKV-NH2, but not VKGILS-NH2, stimulated a rapid concentration-dependent mobilization of intracellular Ca2+ and ERK1/2 phosphorylation and, by 24 h, increases in DNA synthesis, fibronectin secretion, and MCP-1 secretion. These delayed responses appeared to be independent of ERK1/2. Trypsin produced similar rapid but not delayed responses. Trypsinogen was weakly expressed by PTC in the kidney and in culture. In summary, PTC are the main site of PAR-2 expression in the human kidney. In PTC cultures SLIGKV-NH2 initiates proinflammatory and proliferative responses. Trypsinogen expressed within the kidney has the potential to contribute to PAR-2 activation in certain circumstances.
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Affiliation(s)
- David A Vesey
- 1Centre for Kidney Disease Research, University of Queensland Department of Medicine, Princess Alexandra Hospital, Brisbane, Qld 4102, Australia.
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Vesey DA, Cheung CW, Kruger WA, Poronnik P, Gobe G, Johnson DW. Thrombin stimulates proinflammatory and proliferative responses in primary cultures of human proximal tubule cells. Kidney Int 2005; 67:1315-29. [PMID: 15780084 DOI: 10.1111/j.1523-1755.2005.00209.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Fibrin deposition is frequently observed within the tubulointerstitium in various forms of chronic renal disease. This suggests the presence of active components of the coagulation pathway, which may contribute to the progressive deterioration in renal function. The aim of this study was to investigate the proinflammatory and fibroproliferative effects of the coagulation protease thrombin on human proximal tubular cells (PTC) in culture. METHODS Primary cultures of PTC were established from normal kidney tissue and grown under serum-free conditions with or without thrombin or the protease-activated receptor (PAR) activating peptides TFLLRN-NH(2), SLIGKV-NH(2), and SFLLRN-NH(2) (100 to 400 micromol/L). DNA synthesis (thymidine incorporation), intracellular Ca(2+) mobilization (fura-2 fluorimetry), fibronectin secretion [enzyme-linked immunosorbent assay (ELISA), immunoblotting], monocyte chemoattractant protein-1 (MCP-1) secretion (ELISA), and transforming growth factor-beta1 (TGF-beta1) secretion (ELISA) were measured. Reverse transcription-polymerase chain reaction (RT-PCR) was used to assess PAR mRNA expression in these cells. RESULTS Thrombin enhanced DNA synthesis, fibronectin secretion, MCP-1 secretion, and TGF-beta1 secretion in a concentration-dependent manner. Cell injury [lactate dehydrogenase (LDH) release] and cellular protein levels were unaffected. RT-PCR showed that cultures of PTC expressed mRNA transcripts for the thrombin receptors PAR-1 and PAR-3, but not PAR-4. Thrombin and each of the PAR activating peptides enhanced intracellular calcium mobilization. However, the other effects of thrombin were only fully reproduced by the PAR-2-specific peptide, SLIGKV-NH(2), only partially by SFLLRN-NH(2), (a PAR-1 peptide that can activate PAR-2), and not at all by the PAR-1-specific peptide, TFLLRN-NH(2). Thrombin-induced DNA synthesis, fibronectin, and MCP-1 secretion were unaffected by a TGF-beta neutralizing antibody, the matrix metalloproteinase (MMP) inhibitor, GM6001 and the epidermal growth factor (EGF) receptor kinase inhibitor AG1478. CONCLUSION Thrombin initiates both proinflammatory and fibroproliferative responses in human PTC. These responses which are dependent on its protease activity appear not to be mediated by PAR-1 activation, the autocrine action of thrombin-induced TGF-beta1 secretion, MMP activation, or EGF receptor transactivation. The proinflammatory and fibroproliferative actions of thrombin on human PTC may help explain the extent of tubulointerstitial fibrosis observed in kidney diseases where fibrin deposition is evident.
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Affiliation(s)
- David A Vesey
- Department of Renal Medicine, University of Queensland, Princess Alexandra Hospital, Brisbane, Queenlsand, Australia.
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Saad S, Stevens VA, Wassef L, Poronnik P, Kelly DJ, Gilbert RE, Pollock CA. High glucose transactivates the EGF receptor and up-regulates serum glucocorticoid kinase in the proximal tubule. Kidney Int 2005; 68:985-97. [PMID: 16105029 DOI: 10.1111/j.1523-1755.2005.00492.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Serum glucocorticoid regulated kinase (SGK-1) is induced in the kidney in diabetes mellitus. However, its role in the proximal tubule is unclear. This study determined the expression and functional role of SGK-1 in PTCs in high glucose conditions. As the epidermal growth factor (EGF) receptor is activated by both EGF and other factors implicated in diabetic nephropathy, the relationship of SGK-1 with EGFR activity was assessed. METHODS mRNA and protein expression of SGK-1 and mRNA expression of the sodium hydrogen exchanger NHE3 were measured in human PTCs exposed to 5 mmol/L (control) and 25 mmol/L (high) glucose. The effects of SGK-1 on cell growth, apoptosis, and progression through the cell cycle and NHE3 mRNA were examined following overexpression of SGK-1 in PTCs. The role of EGFR activation in observed changes was assessed by phospho-EGFR expression, and response to the EGFR blocker PKI166. SGK-1 expression was then assessed in vivo in a model of streptozotocin-induced diabetes mellitus type 2. RESULTS A total of 25 mmol/L glucose and EGF (10 ng/mL) increased SGK-1 mRNA (P < 0.005 and P < 0.002, respectively) and protein (both P < 0.02) expression. High glucose and overexpression of SGK-1 increased NHE3 mRNA (P < 0.05) and EGFR phosphorylation (P < 0.01), which were reversed by PKI166. SGK-1 overexpression increased PTC growth (P < 0.0001), progression through the cell cycle (P < 0.001), and increased NHE3 mRNA (P < 0.01), which were all reversed with PKI166. Overexpression of SGK-1 also protected against apoptosis induced in the PTCs (P < 0.0001). Up-regulation of tubular SGK-1 mRNA in diabetes mellitus was confirmed in vivo. Oral treatment with PKI166 attenuated this increase by 51%. No EGF protein was detectable in PTCs, suggestive of phosphorylation of the EGFR by high glucose and downstream induction of SGK-1. CONCLUSION The effects of high glucose on PTC proliferation, reduced apoptosis and increased NHE3 mRNA levels are mediated by EGFR-dependent up-regulation of SGK-1.
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Affiliation(s)
- Sonia Saad
- Kolling Institute Royal North Shore Hospital, University of Sydney, Sydney, Australia
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Morais C, Westhuyzen J, Pat B, Gobe G, Healy H. High ambient glucose is effect neutral on cell death and proliferation in human proximal tubular epithelial cells. Am J Physiol Renal Physiol 2005; 289:F401-9. [PMID: 15827344 DOI: 10.1152/ajprenal.00408.2004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In vitro models of diabetic nephropathy that assess the role of hyperglycemia on proximal tubular cell turnover commonly compare cells in a high-glucose medium (25 or 30 mM) with a low-glucose medium (5 to 6.1 mM). Any cellular growth changes observed are usually attributed to the effect of high glucose. We hypothesize that in such experiments, glucose concentrations in the low-glucose medium may decline during the course of the experiments to levels that inhibit cell growth leading to the comparative conclusion that high glucose induces hyperplasia and/or hypertrophy. In this study, primary cultures of human proximal tubular epithelial cells (PTEC) and immortalized HK-2 cells were exposed to low (5 mM) or high (17, 30, or 47 mM) glucose for up to 6 days (PTEC) and 48 h (HK-2). When culture media were not replenished, low glucose induced a significant increase in necrosis and release of lactate dehydrogenase and a decrease in proliferation, metabolic activity, and protein content without any changes in apoptosis. High-glucose media failed to induce any of these changes. Glucose was undetectable in the low-glucose culture medium after 72 h. No significant differences were observed between any of the treatment groups when culture media were replenished daily. We conclude that regular replenishment of culture media is necessary to prevent the emergence of artifactual and misleading differences between high- and low-glucose groups. The current knowledge of the pathophysiology of high glucose based on cell culture systems may need to be reevaluated.
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Affiliation(s)
- Christudas Morais
- Conjoint Renal Laboratory, Queensland Health Pathology Service, Royal Brisbane, Australia
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Vesey DA, Cheung C, Endre Z, Gobé G, Johnson DW. Role of protein kinase C and oxidative stress in interleukin-1beta-induced human proximal tubule cell injury and fibrogenesis. Nephrology (Carlton) 2005; 10:73-80. [PMID: 15705185 DOI: 10.1111/j.1440-1797.2005.00363.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Interleukin (IL)-1beta, a pro-inflammatory macrophage-derived cytokine, is implicated as a key mediator of interstitial fibrosis and tubular loss or injury in progressive renal insufficiency. This study investigates some of the mechanisms of action of IL-1beta on the proximal tubule. METHODS Confluent cultures of primary human proximal tubule cells (PTC) were incubated in serum-free media supplemented with either IL-1beta (0-4 ng/mL), phorbol-12-myristate 13-acetate (PMA, protein kinase C activator) (6.25-100 nmol/L), or vehicle (control), together with a non-specific protein kinase C inhibitor (H7), a specific protein kinase C inhibitor (BIM-1), an anti-oxidant (NAC) or a NADPH oxidase inhibitor (AEBSF). RESULTS Interleukin-1beta-treated PTC exhibited time-dependent increases in fibronectin secretion (ELISA), cell injury (LDH release) and reactive nitrogen species (RNS) release (Griess assay). Proximal tubule cell DNA synthesis (thymidine incorporation) was also significantly suppressed. The effects of IL-1beta, which were reproduced by incubation of PTC with PMA (6.25-100 nmol/L), were blocked by H7 but not by BIM-1. The anti-oxidant (4 mmol/L) partially blocked IL-1beta-induced fibronectin secretion by PTC, but did not affect IL-1beta-induced LDH release, RNS release or growth inhibition. The NADPH oxidase inhibitor (AEBSF) significantly attenuated all observed deleterious effects of IL-1beta on PTC. CONCLUSION Interleukin-1beta directly induces proximal tubule injury, extracellular matrix production and impaired growth. The anti-oxidant, NAC, appears to ameliorate part of the fibrogenic effect of IL-1beta on PTC through mechanisms that do not significantly involve protein kinase C activation or nitric oxide release.
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Affiliation(s)
- David A Vesey
- Department of Renal Medicine, University of Queensland at the Princess Alexandra Hospital, Brisban, Queensland, Australia
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Vesey DA, Cheung C, Cuttle L, Endre Z, Gobe G, Johnson DW. Interleukin-1beta stimulates human renal fibroblast proliferation and matrix protein production by means of a transforming growth factor-beta-dependent mechanism. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 2002; 140:342-50. [PMID: 12434136 DOI: 10.1067/mlc.2002.128468] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
One of the hallmarks of progressive renal disease is the development of tubulointerstitial fibrosis. This is frequently preceded by macrophage infiltration, raising the possibility that macrophages relay fibrogenic signals to resident tubulointerstitial cells. The aim of this study was to investigate the potentially fibrogenic role of interleukin-1beta (IL-1beta), a macrophage-derived inflammatory cytokine, on cortical fibroblasts (CFs). Primary cultures of human renal CFs were established and incubated for 24 hours in the presence or absence of IL-1beta. We found that IL-1beta significantly stimulated DNA synthesis (356.7% +/- 39% of control, P <.003), fibronectin secretion (261.8 +/- 11% of control, P <.005), collagen type 1 production, (release of procollagen type 1 C-terminal-peptide, 152.4% +/- 26% of control, P <.005), transforming growth factor-beta (TGF-beta) secretion (211% +/- 37% of control, P <.01), and nitric oxide (NO) production (342.8% +/- 69% of control, P <.002). TGF-beta (1 ng/mL) and the phorbol ester phorbol 12-myristate 13-acetate (PMA, 25 nmol/L) produced fibrogenic effects similar to those of IL-1beta. Neither a NO synthase inhibitor (N(G)-methyl-l-arginine, 1 mmol/L) nor a protein kinase C (PKC) inhibitor (bis-indolylmaleimide 1, 1 micromol/L) altered the enhanced level of fibronectin secretion or DNA synthesis seen in response to IL-1beta treatment. However, addition of a TGF-beta-neutralizing antibody significantly reduced IL-1beta-induced fibronectin secretion (IL-1beta + IgG, 262% +/- 72% vs IL-1beta + alphaTGF-beta 156% +/- 14%, P <.02), collagen type 1 production (IL-1beta + IgG, 176% +/- 28% vs IL-1beta + alphaTGF-beta, 120% +/- 14%, P <.005) and abrogated IL-1beta-induced DNA synthesis (245% +/- 49% vs 105% +/- 21%, P <.005). IL-1beta significantly stimulated CF DNA synthesis and production of fibronectin, collagen type 1, TGFbeta, and NO. The fibrogenic and proliferative action of IL-1beta on CF appears not to involve activation of PKC or production of NO but is at least partly TGFbeta-dependent.
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Affiliation(s)
- David A Vesey
- Department of Renal Medicine, Princess Alexandra Hospital, Brisbane, Qld, Australia.
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Vesey DA, Cheung CWY, Cuttle L, Endre ZA, Gobé G, Johnson DW. Interleukin-1beta induces human proximal tubule cell injury, alpha-smooth muscle actin expression and fibronectin production. Kidney Int 2002; 62:31-40. [PMID: 12081561 DOI: 10.1046/j.1523-1755.2002.00401.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Tubulointerstitial lesions, characterized by tubular injury, interstitial fibrosis and the appearance of myofibroblasts, are the strongest predictors of the degree and progression of chronic renal failure. These lesions are typically preceded by macrophage infiltration of the tubulointerstitium, raising the possibility that these inflammatory cells promote progressive renal disease through fibrogenic actions on resident tubulointerstitial cells. The aim of the present study, therefore, was to investigate the potentially fibrogenic mechanisms of interleukin-1beta (IL-1beta), a macrophage-derived pro-inflammatory cytokine, on human proximal tubule cells (PTC). METHODS Confluent, quiescent, passage 2 PTC were established in primary culture from histologically normal segments of human renal cortex (N = 11) and then incubated in serum- and hormone-free media supplemented with either IL-1beta (0 to 4 ng/mL) or vehicle (control). RESULTS IL-1beta significantly enhanced fibronectin secretion by up to fourfold in a time- and concentration-dependent fashion. This was accompanied by significant (2.5- to 6-fold) increases in alpha-smooth muscle actin (alpha-SMA) expression, transforming growth factor beta (TGF-beta1) secretion, nitric oxide (NO) production, NO synthase 2 (NOS2) mRNA and lactate dehydrogenase (LDH) release. Cell proliferation was dose-dependently suppressed by IL-1beta. NG-methyl-l-arginine (L-NMMA; 1 mmol/L), a specific inhibitor of NOS, blocked NO production but did not alter basal or IL-1beta-stimulated fibronectin secretion. In contrast, a pan-specific TGF-beta neutralizing antibody significantly blocked the effects of IL-1beta on PTC fibronectin secretion (IL-1beta, 268.1 +/- 30.6 vs. IL-1beta+alphaTGF-beta 157.9 +/- 14.4%, of control values, P < 0.001) and DNA synthesis (IL-1beta 81.0 +/- 6.7% vs. IL-1beta+alphaTGF-beta 93.4 +/- 2.1%, of control values, P < 0.01). CONCLUSION IL-1beta acts on human PTC to suppress cell proliferation, enhance fibronectin production and promote alpha-smooth muscle actin expression. These actions appear to be mediated by a TGF-beta1 dependent mechanism and are independent of nitric oxide release.
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Affiliation(s)
- David A Vesey
- Department of Renal Medicine, Princess Alexandra Hospital, Woolloongabba, Brisbane, Queensland 4102, Australia.
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Machaalani R, Lazzaro V, Duggin GG. The characterisation and uptake of paraquat in cultured baboon kidney proximal tubule cells (bPTC). Hum Exp Toxicol 2001; 20:90-9. [PMID: 11327515 DOI: 10.1191/096032701672136818] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A primary culture of baboon proximal tubule cells (bPTC) was prepared and characterised using LLC-PK1 cells of proximal tubule origin and MDCK cells of distal tubule origin, as positive and negative references, respectively. The proximal tubular origin of the bPTC was determined by morphological studies, immunoperoxidase staining and the expression of proximal tubule markers alkaline phosphatase and gammaglutamyltransferase. The hypothesis that paraquat (PQ) is transported by the bPTC was investigated. The cytotoxic threshold for PQ in these cells was determined and compared to the LLC-PK1 and MDCK cells. Furthermore, this study investigated the transport of the monovalent cation tetraethyl ammonium (TEA) and the polyvalent cation cimetidine in the bPTC and demonstrated their effect on the cellular uptake of PQ. The cytotoxic threshold of PQ in the bPTC, determined by cellular viability studies using the method of Trypan blue exclusion, is 0.05 mM at 2 h incubation. The LC50 after 24 h is 76, 61 and 455 microM for the bPTC, LLC-PK1 and MDCK cells, respectively. This indicates that proximal tubule cells are more susceptible to PQ toxicity compared to distal tubule cells, which is consistent with clinical PQ toxicity where renal damage is found predominantly in the proximal renal tubules. The cations PQ and cimetidine were actively transported by the bPTC. The uptake of PQ (0.05 mM) commenced after 15 min whereas cimetidine (0.5 mM) uptake was evident after 2 min. Furthermore, cimetidine was shown to compete with PQ for uptake in the bPTC. Coincubating PQ (0.05 mM) and cimetidine (0.5 mM) for 60 min resulted in an approximate 50% decrease in PQ uptake. The cation TEA was not transported by the bPTC suggesting either a genetic mutation or complete absence of the transporter for TEA in the cells. The results suggest that PQ may be transported by the same cation transporter as cimetidine and not TEA, indicating PQ uptake in the bPTC to be via a polyvalent organic cation transporter.
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Affiliation(s)
- R Machaalani
- Department of Renal Medicine and Toxicology Unit, Royal Prince Alfred Hospital, Camperdown, Australia
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Jones SC, Saunders HJ, Pollock CA. High glucose increases growth and collagen synthesis in cultured human tubulointerstitial cells. Diabet Med 1999; 16:932-8. [PMID: 10588523 DOI: 10.1046/j.1464-5491.1999.00174.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIMS Altered proximal tubular cell growth and interstitial fibrosis are features of diabetic nephropathy and correlate with disease progression. These observations are poorly understood, although it has been suggested that they are secondary to glomerular disease. The primary aim of this study was to assess the direct effects of high extracellular glucose concentrations on the human tubulointerstitium. METHODS Primary cultures of human proximal tubule cells (PTCs) and cortical fibroblasts (CFs) were grown for 6 days in media containing either 6.1 mmol/l or 25 mmol/l glucose. Cell proliferation, thymidine uptake (a marker of DNA synthesis), protein content and collagen synthesis were measured. RESULTS In PTCs, exposure to high glucose was associated with a 410+/-108% increase in cell numbers (P<0.001); 101+/-24% increase in thymidine uptake per cell (P<0.01) and a 39+/-6% decrease in protein content per cell (P<0.05). Collagen synthesis was increased by 37+/-11% (P<0.05). In CFs, exposure to high glucose was associated with an 80+/-25% increase in cell numbers (P<0.05); 137+/-50% increase in thymidine uptake per cell (P<0.001), with protein content per cell unchanged. Collagen synthesis increased by 37+/-13%; however, the difference was not significant (P = 0.07). There were no differences between control cells exposed to 6.1 mmol/l glucose or an osmotic control (6.1 mmol/l D-glucose +18.9mmol/l L-glucose). CONCLUSIONS Exposure of human PTCs and CFs to high extracellular glucose concentrations results directly in altered cell growth and collagen synthesis that is independent of haemodynamic, glomerular or vascular pathology.
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Affiliation(s)
- S C Jones
- Department of Medicine, University of Sydney, Australia
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15
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Johnson DW, Saunders HJ, Field MJ, Pollock CA. In vitro effects of simvastatin on tubulointerstitial cells in a human model of cyclosporin nephrotoxicity. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:F467-75. [PMID: 10070171 DOI: 10.1152/ajprenal.1999.276.3.f467] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To investigate the possibility that 3-hydroxy-3-methylglutaryl CoA (HMGCoA) reductase inhibitors ameliorate renal disease via direct effects on the tubulointerstitium, primary cultures of human proximal tubule cells (PTC) and renal cortical fibroblasts (CF) were exposed for 24 h to simvastatin (0.1-10 micromol/l) under basal conditions and in the presence of 1,000 ng/ml of cyclosporin (CsA), which we have previously shown to promote in vitro interstitial matrix accumulation at least partially via activation of local cytokine networks. Simvastatin, in micromolar concentrations, engendered cholesterol-independent inhibition of CF and PTC thymidine incorporation and cholesterol-dependent suppression of PTC apical Na+/H+ exchange (NHE) (ethylisopropylamiloride-sensitive apical 22Na+ uptake). Similarly, CF secretion of insulin-like growth factor-I (IGF-I) and IGF binding protein-3 were depressed, whereas CF collagen synthesis ([3H]proline incorporation) and PTC secretion of the fibrogenic cytokines, transforming growth factor-beta1, and platelet-derived growth factor were unaffected. A lower concentration (0.1 micromol/l) of simvastatin did not affect any of the above parameters under basal conditions but completely prevented CsA-stimulated CF collagen synthesis (control, 6.6 +/- 0.6; CsA, 8.3 +/- 0.6; CsA+simvastatin, 6.2 +/- 0.5%; P < 0.05) and IGF-I secretion (89.5 +/- 16.6, 204.7 +/- 57.0, and 94.6 +/- 22.3 ng. mg protein-1. day-1, respectively; P < 0.05). The results suggest that simvastatin exerts direct cholesterol-dependent and -independent effects on the human kidney tubulointerstitium. HMGCoA reductase inhibitors may ameliorate interstitial fibrosis complicating CsA therapy via direct actions on human renal cortical fibroblasts.
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Affiliation(s)
- D W Johnson
- Department of Medicine, University of Sydney, Sydney, Australia 2006
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16
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Gilbert RE, Wilkinson-Berka JL, Johnson DW, Cox A, Soulis T, Wu LL, Kelly DJ, Jerums G, Pollock CA, Cooper ME. Renal expression of transforming growth factor-beta inducible gene-h3 (beta ig-h3) in normal and diabetic rats. Kidney Int 1998; 54:1052-62. [PMID: 9767521 DOI: 10.1046/j.1523-1755.1998.00081.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Transforming growth factor-beta (TGF-beta) has been implicated in the pathogenesis of a number of kidney diseases characterized by glomerulosclerosis and tubulointerstitial fibrosis. TGF-beta is secreted in a latent form requiring extracellular modification to become biologically active. TGF-beta inducible gene-h3 (beta ig-h3) is a recently identified TGF-beta-induced gene product. The present study sought to examine beta ig-h3 expression in normal and diabetic rats. METHODS Beta ig-h3, TGF-beta1 and alpha1 (IV) collagen gene expression were assessed by Northern blot analysis and in situ hybridization in 20 Sprague Dawley rats, randomly assigned to receive streptozotocin (diabetic, N = 11) or citrate buffer alone (control, N = 9) and sacrificed eight months later. The effect of exogenous TGF-beta1 on beta ig-h3 expression was also assessed in cultured proximal tubular cells. RESULTS In situ hybridization localized beta ig-h3 gene expression to the juxtaglomerular apparatus and the pars recta (S3 segment) of proximal tubules in both control and diabetic animals. Kidney TGF-beta 1, beta ig-h3 and alpha1 (IV) collagen mRNA from diabetic rats were increased two- to threefold compared with controls (P < 0.01). There was a significant correlation between TGF-beta1 and beta ig-h3 gene expression in kidneys from diabetic rats (r = 0.73, P = 0.01). In addition, beta ig-h3 mRNA increased in response to exogenous TGF-beta1 in a dose-dependent fashion in cultured proximal tubular cells. CONCLUSION These findings support the hypothesis that biologically active TGF-beta plays a pathogenetic role in diabetic kidney disease and suggest that beta ig-h3 may be a useful index of TGF-beta1 bioactivity in the kidney.
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Affiliation(s)
- R E Gilbert
- University of Melbourne Department of Medicine, Victoria, Australia.
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Johnson DW, Saunders HJ, Baxter RC, Field MJ, Pollock CA. Paracrine stimulation of human renal fibroblasts by proximal tubule cells. Kidney Int 1998; 54:747-57. [PMID: 9734599 DOI: 10.1046/j.1523-1755.1998.00048.x] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
UNLABELLED Paracrine stimulation of human renal fibroblasts by proximal tubule cells. BACKGROUND Interstitial fibrosis strongly predicts the degree and progression of renal failure in human renal disorders. Since active fibrosis tends to initially occur in a peritubular distribution, the possibility that human proximal tubule cells (PTC) relay fibrogenic signals to neighboring cortical fibroblasts was examined in vitro. METHODS Cell proliferation (cell counts and thymidine incorporation), total collagen synthesis (proline incorporation), matrix metalloproteinase (MMP) activity (gelatin zymography), and autocrine secretion of insulin-like growth factor-I (IGF-I) were measured in primary cultures of human cortical fibroblasts cocultured with PTC or exposed to PTC-conditioned media (PTCCM). RESULTS Cell numbers and thymidine incorporation rates were increased in cortical fibroblasts cocultured with PTC (136.4+/-7.3% and 119.3+/-8.2% of control values, respectively, P < 0.05) or incubated in PTC-CM (114.0+/-5.9%, P < 0.05 and 146.7+/-13.3%, P < 0.05, respectively). PTC-CM stimulated cortical fibroblast collagen synthesis (13.5+/-1.0% vs. 10.8+/-0.7%, respectively, N = 24, P < 0.05) and MMP-2 and MMP-9 secretion. Cortical fibroblast secretion of IGF-I binding protein-3 (IGFBP-3), which in turn modulates the autocrine and paracrine actions of IGF-I, was enhanced in the presence of PTC-CM compared with control (1162.2+/-94.2 vs. 969.1+/-58.9 ng/mg protein/day, P < 0.05), but no change was observed in cortical fibroblast secretion of IGFBP-2 (260.9+/-38.8 vs. 290.9+/-36.6 ng/mg protein/day, P = NS) or IGF-I (56.7+/-6.6 vs. 57.0+/-6.8 ng/mg protein/day, P = NS). Human PTC secreted transforming growth factor-beta1 (TGF-beta1) and the AB heterodimer of platelet-derived growth factor (PDGF-AB) in a time-dependent fashion and the augmentation of cortical fibroblasts mitogenesis, collagen synthesis and IGFBP-3 secretion induced by PTC-CM was replicated by exogenous TGF-beta1 and PDGF. Furthermore, the stimulatory effects of PTC on cortical fibroblasts were potentiated in transiently acidified PTC-CM (which activated latent TGF-beta1), and were abrogated by neutralizing antibodies specifically directed against TGF-beta1 and PDGF-AB. Cortical fibroblasts in turn released a soluble factor(s) into cortical fibroblast-conditioned media that reciprocally stimulated PDGF-AB production by PTC (4.79+/-1.55 vs. 0.78+/-.06 ng/mg protein/day, P < 0.05). CONCLUSIONS PTC modulate the biological behavior of neighboring cortical fibroblasts in the human kidney through paracrine mechanisms, which include the production and release of PDGF-AB and TGF-beta1. Renal insults that result in proximal tubule injury may perturb this paracrine interaction, thereby culminating in excessive fibroblast proliferation and interstitial fibrosis.
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Affiliation(s)
- D W Johnson
- Department of Medicine, University of Sydney, and Kolling Institute, Royal North Shore Hospital, Australia
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Johnson DW, Saunders HJ, Brew BK, Poronnik P, Cook DI, Field MJ, Pollock CA. TGF-beta 1 dissociates human proximal tubule cell growth and Na(+)-H+ exchange activity. Kidney Int 1998; 53:1601-7. [PMID: 9607190 DOI: 10.1046/j.1523-1755.1998.00916.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Stimulation of proximal tubule cell (PTC) growth in a variety of physiological and pathological renal conditions is preceded by increased renal production of transforming growth factor-beta 1 (TGF-beta 1) and by augmented tubular sodium transport via activated sodium hydrogen exchange (NHE). Since TGF-beta 1 has been shown to be an important paracrine and autocrine regulator of PTC growth, the hypothesis that TGF-beta 1 modulates basal and mitogen-stimulated PTC growth via an effect on NHE activity was examined. Confluent, quiescent, human PTC were incubated for 24 hours in serum-free media containing vehicle (control) or 1 ng/ml TGF-beta 1, in the presence or absence of 100 ng/ml insulin-like growth factor-1 (IGF-I). Under basal conditions, TGF-beta 1 inhibited thymidine incorporation (73.5 +/- 7.3% of control, P < 0.05), but exerted no effect on cellular protein content (97.4 +/- 10.7% of control), an index of hypertrophy. There was no significant alteration of NHE activity, measured as ethylisopropylamiloride (EIPA)-sensitive H+ efflux (2.72 +/- 0.50 vs. control 3.26 +/- 0.68 mmol/liter/min) or 22Na+ influx (2.20 +/- 0.23 vs. control 2.19 +/- 0.19 nmol/mg protein/min). When co-incubated with IGF-I. TGF-beta 1 induced significant PTC hypertrophy (116.9 +/- 8.2% of control, P < 0.05), which was not seen with either agent alone. TGF-beta 1 counteracted the stimulatory effect of IGF-I on DNA synthesis (TGF-beta 1 + IGF-I 103.0 +/- 7.3% vs. IGF-I alone 181.2 +/- 30.3% of control, P < 0.05), but did not affect IGF-I-stimulated EIPA-sensitive 22Na+ influx (3.63 +/- 0.63 vs. IGF-I alone 3.67 +/- 0.50 nmol/mg protein/min, P = NS, both vs. control 2.19 +/- 0.19 nmol/mg protein/min, P < 0.05). Similar results were obtained when NHE activity was measured as EIPA-sensitive H+ efflux. Moreover, the kinetics of NHE activation by the combination of TGF-beta 1 and IGF-I (involving an increase in Vmax) were identical to that previously found for PTC exposed to IGF-I alone. The study demonstrates that TGF-beta 1 elicits distinct PTC growth responses in the presence and absence of IGF-I, without modification of NHE activity. The combination of predominant PTC hypertrophy and enhanced proximal tubule Na+ reabsorption found in many conditions that are associated with renal growth is likely to require the integrated actions of both TGF-beta 1 and IGF-I.
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Affiliation(s)
- D W Johnson
- Department of Medicine, University of Sydney, New South Wales, Australia
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Johnson DW, Saunders HJ, Field MJ, Pollock CA. Role of insulin-like growth factor binding proteins in human post-nephrectomy proximal tubule cells. J Physiol 1998; 508 ( Pt 2):587-95. [PMID: 9508819 PMCID: PMC2230892 DOI: 10.1111/j.1469-7793.1998.587bq.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
1. In order to determine the role of the insulin-like growth factor-I (IGF-I)/IGF binding protein (IGFBP) axis in the augmentation of tubule growth and function following reductions in nephron mass, primary cultures of human proximal tubule cells (PTCs) were generated from the histologically normal sections of ten surgically removed kidneys. 2. PTC hypertrophy (cellular protein content), DNA synthesis (thymidine incorporation) and apical sodium-hydrogen exchange (NHE) activity (ethylisopropylamiloride-sensitive apical 22Na+ uptake) were measured following 24 h incubation in media supplemented with 10 % pre- or post-nephrectomy sera obtained from these patients. The results were compared with the effects of pre- and post-operative control sera collected from seven patients undergoing retroperitoneal operations not involving removal of renal tissue. 3. Day 1 post-nephrectomy sera promoted a significant 73 % increase in apical NHE activity, which was accompanied by a significant increase in PTC binding of 125I-IGF-I (post- vs. pre-nephrectomy, 163 +/- 6 vs. 142 +/- 4 fmol (mg protein)-1; P < 0.05). Subsequent post-nephrectomy sera significantly stimulated PTC protein content and thymidine incorporation, peaking at day 7 (127.7 +/- 14.0 and 118.4 +/- 9.0 % of pre-nephrectomy values, respectively; P < 0.05). The growth effects were cell specific, as they were not observed with renal cortical fibroblasts. No change was detected in any of these measured variables following exposure to control sera. 4. Serum IGF-I and IGFBP-1 levels did not significantly change over time or between groups. IGFBP-3 levels progressively decreased in both control and nephrectomized sera from pre-operative values of 3580 +/- 305 and 3360 +/- 217 ng ml-1, respectively, to 2670 +/- 341 and 2600 +/- 347 ng ml-1 at 1 week post-operation. Serum IGFBP-2 levels increased to a comparable extent in both controls (day 0 vs. day 7, 2940 +/- 1024 vs. 7010 +/- 2520 ng ml-1; P < 0.01) and nephrectomized patients (day 0 vs. day 7, 3070 +/- 656 vs. 9130 +/- 2010 ng ml-1; P < 0.01). 5. The results indicate that nephrectomy engenders the elaboration of one or more humoral factor(s), which promotes increased binding of IGF-I to PTCs and which may in turn specifically stimulate PTC Na+ transport and growth.
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Affiliation(s)
- D W Johnson
- Department of Medicine, University of Sydney at Royal North Shore Hospital, Sydney, Australia 2006
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Johnson DW, Saunders HJ, Brew BK, Ganesan A, Baxter RC, Poronnik P, Cook DI, Györy AZ, Field MJ, Pollock CA. Human renal fibroblasts modulate proximal tubule cell growth and transport via the IGF-I axis. Kidney Int 1997; 52:1486-96. [PMID: 9407494 DOI: 10.1038/ki.1997.479] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
To determine the paracrine interactions involved in the tubulointerstitial response to progressive renal disease, the role of insulin-like growth factor-I (IGF-I) and its binding proteins (IGFBPs) in in vitro interactions between human proximal tubule cells (PTC) and renal cortical fibroblasts (CF) were studied in primary cell culture. PTC growth and transport were increased in the presence of CF-conditioned media (CF-CM), as shown by increased thymidine incorporation, cellular protein content and sodium-hydrogen exchange (NHE) activity, to 185 +/- 31% (P < 0.01), 150 +/- 18% (P < 0.05) and 195 +/- 27% (P < 0.01) of the control values, respectively. IGF-I was produced by cultured CF at a rate of 64.6 +/- 7.5 ng/mg protein/day. Exogenous IGF-I applied to PTC provoked similar enhancement of growth and NHE activity as CF-CM and the stimulatory effect of CF-CM was blocked by specific immunoneutralization of IGF-I receptors. These receptors were threefold more abundant on PTC basolateral versus apical membranes. IGF binding proteins (IGFBP)-2 and IGFBP-3 were secreted by CF at rates of 694 +/- 88 and 1769 +/- 45 ng/mg/day, with the release of IGFBP-3 being enhanced in the presence of PTC-CM (120.0 +/- 9.7% of control, P < 0.01). Moreover, the addition of CF-CM to PTC increased cell-associated IGFBP-3 on PTC surfaces, without changes in IGF-I receptor numbers or affinity and without changes in PTC mRNA for IGFBP-3. Des(1-3)IGF-I, an analog that binds to the IGF-I receptor but not to IGFBPs, provided a less potent stimulus for PTC growth compared with IGF-I, indicating that cell-associated IGFBP-3 facilitates the action of IGF-I on PTC. The results support important paracrine roles for both IGF-I and IGFBPs in the interstitial regulation of proximal tubule growth and transport.
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MESH Headings
- Antibodies/pharmacology
- Binding, Competitive/immunology
- Biological Transport/physiology
- Blotting, Northern
- Cell Communication/physiology
- Cell Division/physiology
- Cells, Cultured
- Culture Media, Conditioned/pharmacology
- Fibroblasts/chemistry
- Fibroblasts/cytology
- Fibroblasts/metabolism
- Humans
- Insulin-Like Growth Factor Binding Protein 2/metabolism
- Insulin-Like Growth Factor Binding Protein 3/genetics
- Insulin-Like Growth Factor Binding Protein 3/metabolism
- Insulin-Like Growth Factor I/metabolism
- Insulin-Like Growth Factor I/pharmacology
- Kidney Cortex/chemistry
- Kidney Cortex/cytology
- Kidney Cortex/metabolism
- Kidney Tubules, Proximal/chemistry
- Kidney Tubules, Proximal/cytology
- Kidney Tubules, Proximal/metabolism
- Neutralization Tests
- Paracrine Communication/physiology
- Peptide Fragments/pharmacology
- RNA, Messenger/analysis
- Receptor, IGF Type 1/immunology
- Receptor, IGF Type 1/metabolism
- Sodium-Hydrogen Exchangers/metabolism
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Affiliation(s)
- D W Johnson
- Department of Medicine, University of Sydney, Australia
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