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Hanazaki H, Yokota H, Yamagami S, Nakamura Y, Nagaoka T. The Effect of Anti-Autotaxin Aptamers on the Development of Proliferative Vitreoretinopathy. Int J Mol Sci 2023; 24:15926. [PMID: 37958909 PMCID: PMC10647324 DOI: 10.3390/ijms242115926] [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: 09/11/2023] [Revised: 10/25/2023] [Accepted: 10/30/2023] [Indexed: 11/15/2023] Open
Abstract
This study investigated the effect of anti-autotaxin (ATX) aptamers on the development of proliferative vitreoretinopathy (PVR) in both in vivo and in vitro PVR swine models. For the in vitro study, primary retinal pigment epithelial (RPE) cells were obtained from porcine eyes and cultured for cell proliferation and migration assays. For the in vivo study, a swine PVR model was established by inducing retinal detachment and injecting cultured RPE cells (2.0 × 106). Concurrently, 1 week after RPE cell injection, the anti-ATX aptamer, RBM-006 (10 mg/mL, 0.1 mL), was injected twice into the vitreous cavity. Post-injection effects of the anti-ATX aptamer on PVR development in the in vivo swine PVR model were investigated. For the in vitro evaluation, the cultured RPE cell proliferation and migration were significantly reduced at anti-ATX aptamer concentrations of 0.5-0.05 mg and at only 0.5 mg, respectively. Intravitreal administration of the anti-ATX aptamer also prevented tractional retinal detachment caused by PVR in the in vivo PVR model. We observed that the anti-ATX aptamer, RBM-006, inhibited PVR-related RPE cell proliferation and migration in vitro and inhibited the progression of PVR in the in vivo model, suggesting that the anti-ATX aptamer may be effective in preventing PVR.
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Affiliation(s)
- Hirotsugu Hanazaki
- Division of Ophthalmology, Department of Visual Sciences, Nihon University School of Medicine, 30-1 Oyaguchi-Kamicho, Itabashi-ku, Tokyo 173-8610, Japan; (H.H.); (H.Y.); (S.Y.)
| | - Harumasa Yokota
- Division of Ophthalmology, Department of Visual Sciences, Nihon University School of Medicine, 30-1 Oyaguchi-Kamicho, Itabashi-ku, Tokyo 173-8610, Japan; (H.H.); (H.Y.); (S.Y.)
| | - Satoru Yamagami
- Division of Ophthalmology, Department of Visual Sciences, Nihon University School of Medicine, 30-1 Oyaguchi-Kamicho, Itabashi-ku, Tokyo 173-8610, Japan; (H.H.); (H.Y.); (S.Y.)
| | - Yoshikazu Nakamura
- The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, Japan;
- RIBOMIC Inc., Minato-ku, Tokyo 108-0071, Japan
| | - Taiji Nagaoka
- Division of Ophthalmology, Department of Visual Sciences, Nihon University School of Medicine, 30-1 Oyaguchi-Kamicho, Itabashi-ku, Tokyo 173-8610, Japan; (H.H.); (H.Y.); (S.Y.)
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Wang Z, Deng Q, Gu Y, Li M, Chen Y, Wang J, Zhang Y, Zhang J, Hu Q, Zhang S, Chen W, Chen Z, Li J, Wang X, Liang H. Integrated single-nucleus sequencing and spatial architecture analysis identified distinct injured-proximal tubular types in calculi rats. Cell Biosci 2023; 13:92. [PMID: 37208718 DOI: 10.1186/s13578-023-01041-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 05/01/2023] [Indexed: 05/21/2023] Open
Abstract
BACKGROUND Urolithiasis with high prevalence and recurrence rate, has impacts on kidney injury in patients, becomes a socioeconomic and healthcare problem in worldwide. However, the biology of kidney with crystal formation and proximal tubular injury remains essentially unclear. The present study aims to evaluate the cell biology and immune-communications in urolithiasis mediated kidney injury, to provide new insights in the kidney stone treatment and prevention. RESULTS We identified 3 distinct injured-proximal tubular cell types based on the differentially expression injury markers (Havcr1 and lcn2) and functional solute carriers (slc34a3, slc22a8, slc38a3 and slc7a13), and characterized 4 main immune cell types in kidney and one undefined cell population, where F13a1+/high/CD163+/high monocyte & macrophage and Sirpa/Fcgr1a/Fcgr2a+/high granulocyte were the most enriched. We performed intercellular crosstalk analysis based on the snRNA-seq data and explored the potential immunomodulation of calculi stone formation, and founded that the interaction between ligand Gas6 and its receptors (Gas6-Axl, Gas6-Mertk) was specifically observed in the injured-PT1 cells, but not injured-PT2 and -PT3 cells. The interaction of Ptn-Plxnb2 was only observed between the injured-PT3 cells and its receptor enriched cells. CONCLUSIONS Present study comprehensively characterized the gene expression profile in the calculi rat kidney at single nucleus level, identified novel marker genes for all cell types of rat kidney, and determined 3 distinct sub-population of injured-PT clusters, as well as intercellular communication between injured-PTs and immune cells. Our collection of data provides a reliable resource and reference for studies on renal cell biology and kidney disease.
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Affiliation(s)
- Zhu Wang
- Department of Urology, People's Hospital of Longhua Shenzhen, Southern Medical University, Shenzhen, Guangdong, 518109, P.R. China
| | - Qiong Deng
- Department of Urology, People's Hospital of Longhua Shenzhen, Southern Medical University, Shenzhen, Guangdong, 518109, P.R. China
| | - Yanli Gu
- Central Laboratory, People's Hospital of Longhua Shenzhen, Southern Medical University, Shenzhen, Guangdong, 518109, P.R. China
| | - Min Li
- Department of Pathology, People's Hospital of Longhua Shenzhen, Southern Medical University, Shenzhen, Guangdong, 518109, P.R. China
| | - Yeda Chen
- Department of Urology, People's Hospital of Longhua Shenzhen, Southern Medical University, Shenzhen, Guangdong, 518109, P.R. China
| | - Jieyan Wang
- Department of Urology, People's Hospital of Longhua Shenzhen, Southern Medical University, Shenzhen, Guangdong, 518109, P.R. China
| | - Ying Zhang
- Department of Urology, People's Hospital of Longhua Shenzhen, Southern Medical University, Shenzhen, Guangdong, 518109, P.R. China
| | - Jianwen Zhang
- Department of Urology, People's Hospital of Longhua Shenzhen, Southern Medical University, Shenzhen, Guangdong, 518109, P.R. China
| | - Qiyi Hu
- Department of Urology, People's Hospital of Longhua Shenzhen, Southern Medical University, Shenzhen, Guangdong, 518109, P.R. China
| | - Shenping Zhang
- Department of Urology, People's Hospital of Longhua Shenzhen, Southern Medical University, Shenzhen, Guangdong, 518109, P.R. China
| | - Wei Chen
- Department of Urology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong, 518109, P.R. China
| | - Zhenhua Chen
- Department of Urology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong, 518109, P.R. China
| | - Jiaying Li
- Department of Urology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong, 518109, P.R. China
| | - Xisheng Wang
- Department of Urology, People's Hospital of Longhua Shenzhen, Southern Medical University, Shenzhen, Guangdong, 518109, P.R. China.
- Department of Urology, People's Hospital of Longhua, Southern Medical University, 38 Jinglong Jianshe Road, Shenzhen, Guangdong, 518109, P.R. China.
| | - Hui Liang
- Department of Urology, People's Hospital of Longhua Shenzhen, Southern Medical University, Shenzhen, Guangdong, 518109, P.R. China.
- Department of Urology, People's Hospital of Longhua, Southern Medical University, 38 Jinglong Jianshe Road, Shenzhen, Guangdong, 518109, P.R. China.
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Fuchs L, Mausner-Fainberg K, Luban A, Asseyer SE, Golan M, Benhamou M, Volovitz I, Regev K, Vigiser I, Piura Y, Kolb H, Paul F, Karni A. CTGF/CCN2 has a possible detrimental role in the inflammation and the remyelination failure in the early stages of multiple sclerosis. J Neuroimmunol 2022; 371:577936. [DOI: 10.1016/j.jneuroim.2022.577936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Revised: 07/19/2022] [Accepted: 07/24/2022] [Indexed: 11/15/2022]
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Structural and PK-guided identification of indole-based non-acidic autotaxin (ATX) inhibitors exhibiting high in vivo anti-fibrosis efficacy in rodent model. Eur J Med Chem 2021; 227:113951. [PMID: 34742015 DOI: 10.1016/j.ejmech.2021.113951] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/13/2021] [Accepted: 10/23/2021] [Indexed: 11/23/2022]
Abstract
In recent decades, pharmacological targeting of the autotaxin (ATX)/lysophosphatidic acid (LPA) axis accounted for excellent disease management benefits. Herein, to extend the scope of structure-activity relationships (SARs), fifteen indole-based carbamate derivatives (1-15) were prepared to evaluate the ATX inhibitory potency. Among them, compound 4 bearing morpholine moiety was identified as the optimal ATX inhibitor (0.41 nM), superior to the positive control GLPG1690 (2.90 nM). To resolve the intractable issue of poor pharmacokinetic (PK) property, urea moiety was introduced as a surrogate of carbamate which furnished compounds 16-30. The dedicated modification identified the diethanolamine entity 30 with satisfactory water solubility and PK profiles with a minimum sacrifice of ATX inhibition (2.17 nM). The most promising candidate 30 was evaluated for anti-fibrosis effect in a bleomycin challenged mice lung fibrosis model. Upon treatment with 30, the in vivo ATX activity in both lung homogenate and broncheoalveolar fluid (BALF) sample was significantly down-regulated. Furthermore, the gene expression of pro-fibrotic cytokines transforming growth factor-β (TGF-β), interleukin- 6 (IL-6) and tumor necrosis factor-α (TNF-α) in lung tissue was reduced to normal level. Collectively, the promising biological effects may advocate potential application of 30 in fibrosis relevant diseases.
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Geng H, Lan R, Liu Y, Chen W, Wu M, Saikumar P, Weinberg JM, Venkatachalam MA. Proximal tubule LPA1 and LPA2 receptors use divergent signaling pathways to additively increase profibrotic cytokine secretion. Am J Physiol Renal Physiol 2021; 320:F359-F374. [PMID: 33427061 PMCID: PMC7988817 DOI: 10.1152/ajprenal.00494.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 12/17/2020] [Accepted: 12/30/2020] [Indexed: 01/01/2023] Open
Abstract
Lysophosphatidic acid (LPA) increases platelet-derived growth factor-B (PDGFB) and connective tissue growth factor (CTGF) production and secretion by proximal tubule (PT) cells through LPA2 receptor-Gqα-αvβ6-integrin-mediated activation of transforming growth factor-β1 (TGFB1). LPA2, β6-integrin, PDGFB, and CTGF increase in kidneys after ischemia-reperfusion injury (IRI), coinciding with fibrosis. The TGFB1 receptor antagonist SD-208 prevents increases of β6-integrin, TGFB1-SMAD signaling, and PDGFB/CTGF expression after IRI and ameliorates fibrosis (Geng H, Lan R, Singha PK, Gilchrist A, Weinreb PH, Violette SM, Weinberg JM, Saikumar P, Venkatachalam MA. Am J Pathol 181: 1236-1249, 2012; Geng H, Lan R, Wang G, Siddiqi AR, Naski MC, Brooks AI, Barnes JL, Saikumar P, Weinberg JM, Venkatachalam MA. Am J Pathol 174: 1291-1308, 2009). We report now that LPA1 receptor signaling through epidermal growth factor receptor (EGFR)-ERK1/2-activator protein-1 cooperates with LPA2-dependent TGFB1 signaling to additively increase PDGFB/CTGF production and secretion by PT cells. Conversely, inhibition of both pathways results in greater suppression of PDGFB/CTGF production and secretion and promotes greater PT cellular differentiation than inhibiting one pathway alone. Antagonism of the LPA-generating enzyme autotaxin suppressed signaling through both pathways. After IRI, kidneys showed not only more LPA2, nuclear SMAD2/3, and PDGFB/CTGF but also increased LPA1 and autotaxin proteins, together with enhanced EGFR/ERK1/2 activation. Remarkably, the TGFB1 receptor antagonist SD-208 prevented all of these abnormalities excepting increased LPA2. SD-208 inhibits only one arm of LPA signaling: LPA2-Gqα-αvβ6-integrin-dependent production of active TGFB1 and its receptor-bound downstream effects. Consequently, far-reaching protection by SD-208 against IRI-induced signaling alterations and tubule-interstitial pathology is not fully explained by our data. TGFB1-dependent feedforward modulation of LPA1 signaling is one possibility. SD-208 effects may also involve mitigation of injury caused by IRI-induced TGFB1 signaling in endothelial cells and monocytes. Our results have translational implications for using TGFB1 receptor antagonists, LPA1 and LPA2 inhibitors concurrently, and autotaxin inhibitors in acute kidney injury to prevent the development of chronic kidney disease.
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Affiliation(s)
- Hui Geng
- Department of Pathology, University of Texas Health Science Center, San Antonio, Texas
| | - Rongpei Lan
- Department of Pathology, University of Texas Health Science Center, San Antonio, Texas
| | - Yaguang Liu
- Department of Pathology, University of Texas Health Science Center, San Antonio, Texas
| | - Wei Chen
- Department of Pathology, University of Texas Health Science Center, San Antonio, Texas
| | - Meng Wu
- Department of Pathology, University of Texas Health Science Center, San Antonio, Texas
| | - Pothana Saikumar
- Department of Pathology, University of Texas Health Science Center, San Antonio, Texas
| | - Joel M Weinberg
- Department of Medicine, University of Michigan Medical Center, Ann Arbor, Michigan
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Tan Z, Lei H, Guo M, Chen Y, Zhai X. An updated patent review of autotaxin inhibitors (2017-present). Expert Opin Ther Pat 2021; 31:421-434. [PMID: 33342311 DOI: 10.1080/13543776.2021.1867106] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
INTRODUCTION The ATX-LPA axis is an attractive target for therapeutic intervention in a variety of diseases, such as tumor metastasis, fibrosis, pruritus, multiple sclerosis, inflammation, autoimmune conditions, metabolic syndrome, and so on. Accordingly, considerable efforts have been devoted to the development of new chemical entities capable of modulating the ATX-LPA axis. AREAS COVERED This review aims to provide an overview of novel ATX inhibitors reported in patents from September 2016 to August 2020, discussing their structural characteristics and inhibitory potency in vitro and in vivo. EXPERT OPINION In the past four years, the classification of ATX inhibitors based on binding modes has brought great benefits to the discovery of more efficacious inhibitors. In addition to GLPG1690 currently in phase III clinical studies for IPF, BBT-877, and BLD-0409 as potent ATX inhibitors have been enrolled in phase I clinical evaluation; meanwhile, many effective molecules were also reported successively. However, most emerging ATX inhibitors in the last four years are closely analogs of previous entities, such as GLPG1690 and PF-8380, which translate into the urgently identification of ATX inhibitors with diverse structural features and promising properties in the near future.
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Affiliation(s)
- Zehui Tan
- Key Laboratory of Structure-Based Drug Design and Discovery, Ministry of Education, Shenyang Pharmaceutical University, Shenyang, China
| | - Hongrui Lei
- Key Laboratory of Structure-Based Drug Design and Discovery, Ministry of Education, Shenyang Pharmaceutical University, Shenyang, China
| | - Ming Guo
- Key Laboratory of Structure-Based Drug Design and Discovery, Ministry of Education, Shenyang Pharmaceutical University, Shenyang, China
| | - Yuxiang Chen
- Key Laboratory of Structure-Based Drug Design and Discovery, Ministry of Education, Shenyang Pharmaceutical University, Shenyang, China
| | - Xin Zhai
- Key Laboratory of Structure-Based Drug Design and Discovery, Ministry of Education, Shenyang Pharmaceutical University, Shenyang, China
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Love H, Evans R, Humes HD, Roy S, Zent R, Harris R, Wilson M, Fissell WH. Metformin and Inhibition of Transforming Growth Factor-Beta Stimulate In Vitro Transport in Primary Renal Tubule Cells. Tissue Eng Part A 2020; 26:1091-1098. [PMID: 32312181 DOI: 10.1089/ten.tea.2019.0294] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Patient-oriented applications of cell culture include cell therapy of organ failure like chronic renal failure. Clinical deployment of a cell-based device for artificial renal replacement requires qualitative and quantitative fidelity of a cultured cell to its in vivo counterpart. Active specific apicobasal ion transport reabsorbs 90-99% of the filtered load of salt and water in the kidney. In a bioengineered kidney, tubular transport concentrates wastes and eliminates the need for hemodialysis, but renal tubule cells in culture transport little or no salt and water. We previously identified transforming growth factor-beta as a signaling pathway necessary for in vitro differentiation of renal tubule cells. Inhibition of TGF-β receptor-1 led to active inhabitable electrolyte and water transport by primary human renal tubule epithelial cells in vitro. Addition of metformin increased transport, in the context of a transient effect on 5' AMP-activated kinase phosphorylation. The signals that undermine in vitro differentiation are complex, but susceptible to pharmacologic intervention. This achievement overcomes a major hurdle limiting the development of a bioreactor of cultured cells for renal replacement therapy that encompasses not only endocrine and metabolic functions but also transport and excretion. Impact statement Clinical tissue engineering requires functional fidelity of the cultured cell to its in vivo counterpart, but this has been elusive in renal tissue engineering. Typically, renal tubule cells in culture have a flattened morphology and do not express key transporters essential to their function. In this study, we build on our prior work by using small molecules to modulate pathways affected by substrate elasticity. In doing so, we are able to enhance differentiation of these cells on conventional noncompliant substrates and show transport. These results are fundamentally enabling a new generation of cell-based renal therapies.
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Affiliation(s)
- Harold Love
- Department of Medicine, Division of Nephrology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Rachel Evans
- Department of Medicine, Division of Nephrology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | | | - Shuvo Roy
- Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, USA
| | - Roy Zent
- Department of Medicine, Division of Nephrology, Vanderbilt University Medical Center, Nashville, Tennessee, USA.,Department of Medicine, Veterans Affairs Medical Center, Nashville, Tennessee, USA
| | - Raymond Harris
- Department of Medicine, Division of Nephrology, Vanderbilt University Medical Center, Nashville, Tennessee, USA.,Department of Medicine, Veterans Affairs Medical Center, Nashville, Tennessee, USA
| | - Matthew Wilson
- Department of Medicine, Division of Nephrology, Vanderbilt University Medical Center, Nashville, Tennessee, USA.,Department of Medicine, Veterans Affairs Medical Center, Nashville, Tennessee, USA
| | - William Henry Fissell
- Department of Medicine, Division of Nephrology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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Receptor-independent modulation of TGF-β-induced pro-fibrotic pathways by relaxin-2 in human primary tubular epithelial cells. Cell Tissue Res 2018; 374:619-627. [PMID: 30078103 DOI: 10.1007/s00441-018-2904-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 07/24/2018] [Indexed: 10/28/2022]
Abstract
Renal tubular epithelial cells actively contribute to the development of renal fibrosis and may be targeted by anti-fibrotic drugs. Relaxin-2 (RLX2) applied as recombinant protein is suggested to be renoprotective. Therefore, we investigated whether human primary tubular epithelial cells (hPTEC) obtained from various donors were target cells for the anti-fibrotic actions of RLX2. Treatment of hPTEC with RLX2 reduced the TGF-β1-induced secretion of the pro-fibrotic factor CTGF (connective tissue growth factor) and inhibited fibronectin synthesis and secretion. Furthermore, metalloproteinase MMP2 secretion was increased, with no effect on MMP9. Considerable differences were observed between hPTEC obtained from different donors. Therefore, expression of the relaxin family peptide receptor RXFP1, the major mediator of renal RLX2 effects, was analyzed. A validated antibody detected a double band of 80-90 kDa in cellular homogenates by Western blotting. Expression of the detected protein was not altered by incubation with TGF-β1 and RLX2-induced modulation of CTGF expression did not correlate with the putative receptor expression. Therefore, relaxin family receptors RXFP1-4 were assessed by RNA-seq analysis. No evidence was found for mRNA expression of any of these receptors in several hPTEC preparations. Lack of RXFP1 mRNA was confirmed by qPCR using mRNA obtained from THP-1 cells as positive control. Our data thus provide evidence for primary renal human tubular epithelial cells as targets for the anti-fibrotic actions of RLX2. However, anti-fibrotic effects were observed at micromolar concentrations of RLX2 and shown to be independent of RXFP1 expression.
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HIF stabilization inhibits renal epithelial cell migration and is associated with cytoskeletal alterations. Sci Rep 2018; 8:9497. [PMID: 29934555 PMCID: PMC6015081 DOI: 10.1038/s41598-018-27918-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 06/13/2018] [Indexed: 11/23/2022] Open
Abstract
Acute kidney injury (AKI) is a common and potentially lethal complication in the hospitalized patients, with hypoxic injury being as a major cause. The loss of renal tubular epithelial cells (TEC), one of the AKI hallmarks, is potentially followed by tubular regeneration process orchestrated by the remaining uninjured TECs that undergo proliferation and migration. In this study, we used human primary TEC to investigate the initiation of tubular cell migration and associated cytoskeletal alterations in response to pharmacological HIF stabilization which resembles the pathophysiology of hypoxia. Tubular cells have been shown to migrate as cohorts in a wound healing assay. Importantly, cells of distal tubular origin moved faster than those of proximal origin. HIF stabilization impaired TEC migration, which was confirmed by live single cell tracking. HIF stabilization significantly reduced tubular cell migration velocity and promoted cell spreading. In contrast to the control conditions, HIF stabilization induced actin filaments rearrangement and cell adhesion molecules including paxillin and focal adhesion kinase. Condensed bundling of keratin fibers was also observed, while the expression of different types of keratins, phosphorylation of keratin 18, and the microtubule structure were not altered. In summary, HIF stabilization reduced the ability of renal tubular cells to migrate and led to cytoskeleton reorganization. Our data suggested an important involvement of HIF stabilization during the epithelial migration underlying the mechanism of renal regeneration in response to AKI.
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Abstract
Lysophosphatidic acid (LPA) is a bioactive phospholipid that can exert diverse biological effects in various diseased states of the kidney by activating at least six cognate G protein-coupled receptors and its complex network of heterotrimeric G proteins. In many models of acute and chronic kidney injury, pathological elevations in LPA promotes abnormal changes in renal tubular epithelial cell architecture by activating apoptotic signaling, recruits immune cells to the site of injury, and stimulates profibrotic signaling by increasing gene transcription. In renal cancers, LPA can promote vascular cell proliferation and tumor cell invasion. In this review, a summary will be provided to describe the involvement of LPA, its synthetic enzymes, and its associated receptors in normal and diseased kidneys. Further elucidation of the LPA system may open new doors in developing a lipid-receptor therapeutic platform for kidney diseases.
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Affiliation(s)
- Frank Park
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee
| | - Duane D Miller
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee
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Kiwanuka E, Junker JP, Eriksson E. Transforming growth factor β1 regulates the expression of CCN2 in human keratinocytes via Smad-ERK signalling. Int Wound J 2017; 14:1006-1018. [PMID: 28371159 DOI: 10.1111/iwj.12749] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 03/04/2017] [Indexed: 01/22/2023] Open
Abstract
Connective tissue growth factor (CCN2/CTGF) and transforming growth factor β1 (TGF-β1) are important regulators of skin wound healing, but controversy remains regarding their expression in epithelial cell lineages. Here, we investigate the expression of CCN2 in keratinocytes during reepithelialisation and its regulation by TGF-β1. CCN2 was detected in the epidermis of healing full-thickness porcine wounds. Human keratinocytes were incubated with or without 10 ng/ml TGF-β1, and signalling pathways were blocked with 10-μM SIS3 or 20-μM PD98059. Semi-quantitative real-time PCR was used to study CCN2 mRNA expression, and western blot was used to measure CCN2, phosphorylated-ERK1/2, ERK1/2, phosphorylated-Smad3 and Smad2/3 proteins. CCN2 was transiently expressed in neoepidermis at the leading edge of the wound in vivo. In vitro, CCN2 expression was induced by TGF-β1 at 2 hours (7·5 ± 1·9-fold mRNA increase and 3·0 ± 0·6-fold protein increase) and 12 hours (5·4 ± 1·9-fold mRNA increase and 3·3 ± 0·6-fold protein increase). Compared with inhibiting the SMAD pathway, inhibiting the mitogen-activated protein kinase (MAPK) pathway was more effective in reducing TGF-β1-induced CCN2 mRNA and protein expression. Inhibition of the MAPK pathway had minimal impact on the activity of the SMAD pathway. CCN2 is expressed in keratinocytes in response to tissue injury or TGF-β1. In addition, TGF-β1 induces CCN2 expression in keratinocytes through the ras/MEK/ERK pathway. A complete understanding of CCN2 expression in keratinocytes is critical to developing novel therapies for wound healing and cutaneous malignancy.
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Affiliation(s)
- Elizabeth Kiwanuka
- Department of Plastic Surgery, Rhode Island Hospital, Brown University School of Medicine, Providence, RI, USA
| | - Johan Pe Junker
- Center for Disaster Medicine and Traumatology, Department of Clinical and Experimental Medicine, Linköping University Hospital, Linköping, Sweden
| | - Elof Eriksson
- Division of Plastic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
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Muehlich S, Rehm M, Ebenau A, Goppelt-Struebe M. Synergistic induction of CTGF by cytochalasin D and TGFβ-1 in primary human renal epithelial cells: Role of transcriptional regulators MKL1, YAP/TAZ and Smad2/3. Cell Signal 2016; 29:31-40. [PMID: 27721022 DOI: 10.1016/j.cellsig.2016.10.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 09/26/2016] [Accepted: 10/06/2016] [Indexed: 02/08/2023]
Abstract
Changes in cell morphology that involve alterations of the actin cytoskeleton are a hallmark of diseased renal tubular epithelial cells. While the impact of actin remodeling on gene expression has been analyzed in many model systems based on cell lines, this study investigated human primary tubular epithelial cells isolated from healthy parts of tumor nephrectomies. Latrunculin B (LatB) and cytochalasin D (CytoD) were used to modulate G-actin levels in a receptor-independent manner. Both compounds (at 0.5μM) profoundly altered F-actin structures in a Rho kinase-dependent manner, but only CytoD strongly induced the pro-fibrotic factor CTGF (connective tissue growth factor). CTGF induction was dependent on YAP as shown by transient downregulation experiments. However, CytoD did not alter the nuclear localization of either YAP or TAZ, whereas LatB reduced nuclear levels particularly of TAZ. CytoD modified MKL1, a coactivator of serum response factor (SRF) regulating CTGF induction, and promoted its nuclear localization. TGFβ-1 is one of the major factors involved in tubulointerstitial disease and an inducer of CTGF. Preincubation with CytoD but not LatB synergistically enhanced the TGFβ-1-stimulated synthesis of CTGF, both in cells cultured on plastic dishes as well as in polarized epithelial cells. CytoD had no direct effect on the phosphorylation of Smad2/3, but facilitated their phosphorylation and thus activation by TGFβ-1. Our present findings provide evidence that morphological alterations have a strong impact on cellular signaling of one of the major pro-fibrotic factors, TGFβ-1. However, our data also indicate that changes in cell morphology per se cannot predict those interactions which are critically dependent on molecular fine tuning of actin reorganization.
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Affiliation(s)
- Susanne Muehlich
- Walther Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians-University Munich, Goethestrasse 33, D-80336 München, Germany
| | - Margot Rehm
- Department of Nephrology and Hypertension, Friedrich-Alexander-Universität Erlangen-Nürnberg, Loschgestrasse 8, D-91054 Erlangen, Germany
| | - Astrid Ebenau
- Department of Nephrology and Hypertension, Friedrich-Alexander-Universität Erlangen-Nürnberg, Loschgestrasse 8, D-91054 Erlangen, Germany
| | - Margarete Goppelt-Struebe
- Department of Nephrology and Hypertension, Friedrich-Alexander-Universität Erlangen-Nürnberg, Loschgestrasse 8, D-91054 Erlangen, Germany.
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Preisser F, Giehl K, Rehm M, Goppelt-Struebe M. Inhibitors of oxygen sensing prolyl hydroxylases regulate nuclear localization of the transcription factors Smad2 and YAP/TAZ involved in CTGF synthesis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2027-36. [DOI: 10.1016/j.bbamcr.2016.05.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 04/25/2016] [Accepted: 05/03/2016] [Indexed: 11/27/2022]
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14
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Cicha I, Scheffler L, Ebenau A, Lyer S, Alexiou C, Goppelt-Struebe M. Mitoxantrone-loaded superparamagnetic iron oxide nanoparticles as drug carriers for cancer therapy: Uptake and toxicity in primary human tubular epithelial cells. Nanotoxicology 2015; 10:557-66. [DOI: 10.3109/17435390.2015.1095364] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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15
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Gahr S, Mayr C, Kiesslich T, Illig R, Neureiter D, Alinger B, Ganslmayer M, Wissniowski T, Fazio PD, Montalbano R, Ficker JH, Ocker M, Quint K. The pan-deacetylase inhibitor panobinostat affects angiogenesis in hepatocellular carcinoma models via modulation of CTGF expression. Int J Oncol 2015. [PMID: 26202945 DOI: 10.3892/ijo.2015.3087] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Post-translational modifications of chromatin components are significantly involved in the regulation of tumor suppressor gene and oncogene expression. Connective tissue growth factor (CTGF) is an epigenetically regulated growth factor with functions in angiogenesis and cell-matrix interactions and plays a pivotal role in hepatocellular carcinoma (HCC). The pharmacologic inhibition of histone and protein deacetylases represents a new approach to interfere with pathways of apoptosis and angiogenesis. We investigated the effect of the pan-deacetylase inhibitor panobinostat (LBH589) on human HCC cell lines HepG2 (p53wt) and Hep3B (p53null) and in a subcutaneous xenograft model and explored the influence on angiogenesis. Specimens were characterized by quantitative real-time PCR. Protein was separated for western blotting against CTGF, VEGF, VEGF receptor-1 (VEGFR-1/FLT-1), VEGF receptor-2 (VEGFR-2/KDR), MAPK and phospho-MAPK. In vivo, HepG2 cells were xenografted to NMRI mice and treated with daily i.p. injections of 10 mg/kg panobinostat. After 1, 7 and 28 days, real-time PCR was performed. Immunohistochemistry and western blotting were examined after 28 days. An increased significant expression of CTGF was only seen after 24 h treatment with 0.1 µM panobinostat in HepG2 cells and Hep3B cells, whereas after 72 h treatment CTGF expression clearly decreased. In the xenografts, treatment with panobinostat showed a minimal CTGF expression after 1 day and 4 weeks, respectively. In vitro as well as in vivo, VEGF was not affected by panobinostat treatment at any time. In conclusion, panobinostat influences extracellular signaling cascades via CTGF-dependent pathways.
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Affiliation(s)
- Susanne Gahr
- Department of Medicine 1, University Hospital Erlangen, Erlangen, Germany
| | - Christian Mayr
- Laboratory for Tumour Biology and Experimental Therapies, Paracelsus Medical University, Salzburg, Austria
| | - Tobias Kiesslich
- Laboratory for Tumour Biology and Experimental Therapies, Paracelsus Medical University, Salzburg, Austria
| | - Romana Illig
- Institute of Pathology, Salzburger Landeskliniken, Paracelsus Private Medical University, Salzburg, Austria
| | - Daniel Neureiter
- Institute of Pathology, Salzburger Landeskliniken, Paracelsus Private Medical University, Salzburg, Austria
| | - Beate Alinger
- Institute of Pathology, Salzburger Landeskliniken, Paracelsus Private Medical University, Salzburg, Austria
| | - Marion Ganslmayer
- Department of Medicine 1, University Hospital Erlangen, Erlangen, Germany
| | - Till Wissniowski
- Department of Medicine 1, University Hospital Erlangen, Erlangen, Germany
| | - Pietro Di Fazio
- Institute for Surgical Research, Phillips University Marburg, Marburg, Germany
| | - Roberta Montalbano
- Institute for Surgical Research, Phillips University Marburg, Marburg, Germany
| | - Joachim H Ficker
- Klinikum Nuernberg, Department of Respiratory Medicine, Allergology and Sleep Medicine, Nuremberg, Germany
| | - Matthias Ocker
- Department of Medicine 1, University Hospital Erlangen, Erlangen, Germany
| | - Karl Quint
- Department of Medicine 1, University Hospital Erlangen, Erlangen, Germany
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Giehl K, Keller C, Muehlich S, Goppelt-Struebe M. Actin-mediated gene expression depends on RhoA and Rac1 signaling in proximal tubular epithelial cells. PLoS One 2015; 10:e0121589. [PMID: 25816094 PMCID: PMC4376694 DOI: 10.1371/journal.pone.0121589] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 02/14/2015] [Indexed: 12/29/2022] Open
Abstract
Morphological alterations of cells can lead to modulation of gene expression. An essential link is the MKL1-dependent activation of serum response factor (SRF), which translates changes in the ratio of G- and F-actin into mRNA transcription. SRF activation is only partially characterized in non-transformed epithelial cells. Therefore, the impact of GTPases of the Rho family and changes in F-actin structures were analyzed in renal proximal tubular epithelial cells. Activation of SRF signaling was compared to the regulation of a known MKL1/SRF target gene, connective tissue growth factor (CTGF). In the human proximal tubular cell line HKC-8 overexpression of two actin mutants either favoring or preventing the formation of F-actin fibers regulated SRF-mediated transcription as well as CTGF expression. Only overexpression of constitutively active RhoA activated SRF-dependent gene expression whereas no effect was detected upon overexpression of Rac1 mutants. To elucidate the functional role of Rho kinases as downstream mediators of RhoA, pharmacological inhibition and genetic inhibition by transient siRNA knock down were compared. Upon stimulation with lysophosphatidic acid (LPA) Rho kinase inhibitors partially suppressed SRF-mediated transcription, whereas interference with Rho kinase expression by siRNA reduced activation of SRF, but barely affected CTGF expression. Together with the partial inhibition of CTGF expression by the pharmacological inhibitors Y27432 and H1154, Rho kinases seem to be less important in mediating RhoA signaling related to CTGF expression in HKC-8 epithelial cells. Short term pharmacological inhibition of Rac1 activity by EHT1864 reduced SRF-dependent CTGF expression in HKC-8 cells, but was overcome by a stimulatory effect after prolonged incubation after 4-6 h. Similarly, human primary cells of proximal but not of distal tubular origin showed inhibitory as well as stimulatory effects of Rac1 inhibition. Thus, RhoA signaling activates MKL1-SRF-mediated CTGF expression in proximal tubular cells, whereas Rac1 signaling is more complex with adaptive cellular responses.
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Affiliation(s)
- Klaudia Giehl
- Signal Transduction of Cellular Motility, Internal Medicine V, Justus-Liebig-University Giessen, Giessen, Germany
| | - Christof Keller
- Department of Nephrology and Hypertension, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Susanne Muehlich
- Walther Straub Institute of Pharmacology and Toxicology, Ludwig-Maximilians-University, Munich, Germany
| | - Margarete Goppelt-Struebe
- Department of Nephrology and Hypertension, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
- * E-mail:
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17
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Yang Z, Sun L, Nie H, Liu H, Liu G, Guan G. Connective tissue growth factor induces tubular epithelial to mesenchymal transition through the activation of canonical Wnt signaling in vitro. Ren Fail 2014; 37:129-35. [PMID: 25296105 DOI: 10.3109/0886022x.2014.967699] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Overwhelming evidences suggest epithelial to mesenchymal transition (EMT) of tubular epithelial cells contributes to renal fibrosis of chronic kidney disease (CKD). Connective tissue growth factor (CTGF) plays an important role in the pathogenesis of EMT. However, the molecular mechanisms that regulate cell behaviors are not clear. OBJECTIVE The purpose of this study was to investigate whether CTGF induces EMT via activation of canonical Wnt signaling in renal tubular epithelial cells. METHODS Human renal proximal tubular epithelial cells (HK-2) were divided into control group, CTGF group and dickkopf (Dkk)-1 plus CTGF group. We assessed the biological changes of canonical Wnt signaling, including phosphorylation of low-density lipoprotein receptor-related protein (LRP6) and glycogen synthase kinase-3β (GSK-3β) and accumulation and nuclear localization of β-catenin. Meanwhile, morphological changes of the three groups were observed and tubular EMT was further confirmed by detecting the expression of α-SMA and E-cadherin. RESULTS The phosphorylation levels of LRP6 and GSK-3β and the expression of β-catenin in CTGF group were higher than control group (p < 0.05). The accumulation and nuclear localization of β-catenin was induced in CTGF group. Meanwhile, CTGF group cells showed a mesenchymal morphological phenotype and exhibited increased expressions of E-cadherin and decreased expressions of α-SMA compared to control group (p < 0.05), suggesting tubular EMT. Furthermore, we also found that Dkk-1 blocked the above CTGF's effects by binding with LRP6. CONCLUSION CTGF induces EMT via activation of canonical Wnt signaling in HK-2 cells in vitro, which may play an important role in the renal fibrosis of CKD.
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Affiliation(s)
- Zhiying Yang
- Nephrology Research Institute of Shandong University, The Second Hospital of Shandong University, Shandong University , Jinan, Shandong , China
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Cicha I, Zitzmann R, Goppelt-Struebe M. Dual inhibition of Src family kinases and Aurora kinases by SU6656 modulates CTGF (connective tissue growth factor) expression in an ERK-dependent manner. Int J Biochem Cell Biol 2013; 46:39-48. [PMID: 24275091 DOI: 10.1016/j.biocel.2013.11.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2013] [Revised: 10/25/2013] [Accepted: 11/05/2013] [Indexed: 10/26/2022]
Abstract
Src kinases are regulators of the expression of connective tissue growth factor (CTGF/CCN2), which plays a role in fibrotic injuries. The aim of the present study was to evaluate the potential of SU6656, a dual inhibitor of Src family and Aurora kinases, to interfere with the synthesis of this pro-fibrotic factor. SU6656 impaired TGF-β-mediated upregulation of CTGF mRNA and protein in proximal epithelial HKC-8 cells, and also reduced CTGF expression in cells exposed to autocrine growth factors. In association with the inhibition of Src family kinases and diminished focal adhesion kinase activity, adherence of the cells was reduced. Furthermore, SU6656 interfered with Aurora kinase activity resulting in inhibition of cell division and formation multilobular nuclei after 24h. Comparable alterations were observed in primary tubular cells. When cell division was inhibited by SU6656 or ZM447439, a specific inhibitor of Aurora kinases, CTGF levels were back to control or even increased after 48h. The activity of RhoA-Rho kinase and ERK signaling was analyzed to delineate the signaling pathways responsible for the biphasic regulation of CTGF. While Rho kinase was not significantly altered by SU6656, ERK activity was inhibited in the early phase and increased after 24-48h. ERK activity correlated with secreted CTGF. As ZM447439 increased ERK activity only after 48h, cellular reorganization is likely responsible for triggering the ERK-dependent upregulation of CTGF. Taken together, in non-transformed epithelial cells, SU6656 modulates the expression of the pro-fibrotic factor CTGF in a time-dependent manner by inhibition of Src kinases and Aurora kinases.
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Affiliation(s)
- Iwona Cicha
- Department of Cardiology and Angiology, Universitätsklinikum Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg, Schwabachanlage 10, 91054 Erlangen, Germany.
| | - Rita Zitzmann
- Department of Nephrology and Hypertension, Universitätsklinikum Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg, Loschgestrasse 8, D-91054 Erlangen, Germany.
| | - Margarete Goppelt-Struebe
- Department of Nephrology and Hypertension, Universitätsklinikum Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg, Loschgestrasse 8, D-91054 Erlangen, Germany.
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Kiwanuka E, Andersson L, Caterson EJ, Junker JPE, Gerdin B, Eriksson E. CCN2 promotes keratinocyte adhesion and migration via integrin α5β1. Exp Cell Res 2013; 319:2938-46. [DOI: 10.1016/j.yexcr.2013.08.021] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2013] [Revised: 08/06/2013] [Accepted: 08/07/2013] [Indexed: 10/26/2022]
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20
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Kiwanuka E, Hackl F, Caterson EJ, Nowinski D, Junker JPE, Gerdin B, Eriksson E. CCN2 is transiently expressed by keratinocytes during re-epithelialization and regulates keratinocyte migration in vitro by the ras-MEK-ERK signaling pathway. J Surg Res 2013; 185:e109-19. [PMID: 24079812 DOI: 10.1016/j.jss.2013.05.065] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Revised: 05/08/2013] [Accepted: 05/15/2013] [Indexed: 12/01/2022]
Abstract
BACKGROUND CCN2 (previously known as connective tissue growth factor) is a multifunctional matricellular protein that has numerous effects on cell life and cell interactions with the connective tissue. Although the importance of CCN2 for the fibrotic process in wound healing has been well studied, the involvement of CCN2 in keratinocyte function has not yet been explored. Therefore, the aim of the present study was to investigate the role of CCN2 in the epidermis during wound healing. MATERIALS AND METHODS Immunohistochemistry was done on sections from full-thickness porcine wounds. The effect of CCN2 on the migration of cultured human keratinocytes exposed to scratch wounds, the effect on phosphorylation of extracellular signal-related kinases (ERK), and the effect of adding inhibitors to the ERK/mitogen-activated protein kinase pathway to human keratinocytes were studied. RESULTS The CCN2 protein was transiently expressed in vivo at the leading keratinocyte edge during re-epithelialization of full-thickness porcine wounds. In vitro, exogenous addition of CCN2 to human keratinocyte cultures regulated keratinocyte migration and resulted in phosphorylation of ERK. The addition of inhibitors of ERK/mitogen-activated protein kinase counteracted the effect of CCN2 on migration. CONCLUSIONS CCN2 was transiently expressed at the leading keratinocyte edge in vivo. The biologic importance of this was supported in vitro, because CCN2 regulated human keratinocyte migration through activation of the Ras-mitogen-activated protein kinase kinase-ERK signal transduction pathway.
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Affiliation(s)
- Elizabeth Kiwanuka
- Division of Plastic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts; Department of Surgical Sciences, Plastic Surgery Unit, Uppsala University, Uppsala, Sweden
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Kay P, Yang YC, Paraoan L. Directional protein secretion by the retinal pigment epithelium: roles in retinal health and the development of age-related macular degeneration. J Cell Mol Med 2013; 17:833-43. [PMID: 23663427 PMCID: PMC3822888 DOI: 10.1111/jcmm.12070] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Accepted: 03/24/2013] [Indexed: 11/29/2022] Open
Abstract
The structural and functional integrity of the retinal pigment epithelium (RPE) is fundamental for maintaining the function of the neuroretina. These specialized cells form a polarized monolayer that acts as the retinal–blood barrier, separating two distinct environments with highly specialized functions: photoreceptors of the neuroretina at the apical side and Bruch's membrane/highly vascularized choriocapillaris at the basal side. The polarized nature of the RPE is essential for the health of these two regions, not only in nutrient and waste transport but also in the synthesis and directional secretion of proteins required in maintaining retinal homoeostasis and function. Although multiple malfunctions within the RPE cells have been associated with development of age-related macular degeneration (AMD), the leading cause of legal blindness, clear causative processes have not yet been conclusively characterized at the molecular and cellular level. This article focuses on the involvement of directionally secreted RPE proteins in normal functioning of the retina and on the potential association of incorrect RPE protein secretion with development of AMD. Understanding the importance of RPE polarity and the correct secretion of essential structural and regulatory components emerge as critical factors for the development of novel therapeutic strategies targeting AMD.
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Affiliation(s)
- Paul Kay
- Department of Eye and Vision Science, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, UK
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