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Liberski S, Confalonieri F, Cofta S, Petrovski G, Kocięcki J. Ocular Changes in Cystic Fibrosis: A Review. Int J Mol Sci 2024; 25:6692. [PMID: 38928397 PMCID: PMC11203677 DOI: 10.3390/ijms25126692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Revised: 06/10/2024] [Accepted: 06/11/2024] [Indexed: 06/28/2024] Open
Abstract
Cystic fibrosis (CF), also known as mucoviscidosis, is the most common autosomal recessive genetic disease in the Caucasian population, with an estimated frequency of 1:2000-3000 live births. CF results from the mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) gene localized in the long arm of chromosome 7. The product of CFTR gene expression is CFTR protein, an adenosine triphosphate (ATP)-binding cassette (ABC) transporter that regulates the transport of chloride ions (Cl-) across the apical cell membrane. Primary manifestations of CF include chronic lung and pancreas function impairment secondary to the production of thick, sticky mucus resulting from dehydrated secretions. It is well known that CF can cause both anterior and posterior ocular abnormalities. Conjunctival and corneal xerosis and dry eye disease symptoms are the most characteristic manifestations in the anterior segment. In contrast, the most typical anatomical and functional changes relating to the posterior segment of the eye include defects in the retinal nerve fiber layer (RNFL), vascular abnormalities, and visual disturbances, such as reduced contrast sensitivity and abnormal dark adaptation. However, the complete background of ophthalmic manifestations in the course of CF has yet to be discovered. This review summarizes the current knowledge regarding ocular changes in cystic fibrosis.
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Affiliation(s)
- Slawomir Liberski
- Department of Ophthalmology, Poznan University of Medical Sciences, A. Szamarzewskiego 84, 61-848 Poznan, Poland;
| | - Filippo Confalonieri
- Department of Ophthalmology, IRCCS Humanitas Research Hospital, 20089 Rozzano, Milan, Italy;
- Department of Biomedical Sciences, Humanitas University, 20090 Pieve Emanuele, Milan, Italy
- Center for Eye Research and Innovative Diagnostics, Department of Ophthalmology, Institute for Clinical Medicine, University of Oslo, Kirkeveien 166, 0450 Oslo, Norway;
- Department of Ophthalmology, Oslo University Hospital, Kirkeveien 166, 0450 Oslo, Norway
| | - Szczepan Cofta
- Department of Respiratory Medicine, Allergology and Pulmonary Oncology, Poznan University of Medical Sciences, A. Szamarzewskiego 84, 61-848 Poznan, Poland;
| | - Goran Petrovski
- Center for Eye Research and Innovative Diagnostics, Department of Ophthalmology, Institute for Clinical Medicine, University of Oslo, Kirkeveien 166, 0450 Oslo, Norway;
- Department of Ophthalmology, Oslo University Hospital, Kirkeveien 166, 0450 Oslo, Norway
| | - Jarosław Kocięcki
- Department of Ophthalmology, Poznan University of Medical Sciences, A. Szamarzewskiego 84, 61-848 Poznan, Poland;
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Thompson P, Vilkelyte V, Woronkowicz M, Tavakoli M, Skopinski P, Roberts H. Adenylyl Cyclase in Ocular Health and Disease: A Comprehensive Review. BIOLOGY 2024; 13:445. [PMID: 38927325 PMCID: PMC11200476 DOI: 10.3390/biology13060445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2024] [Revised: 06/12/2024] [Accepted: 06/14/2024] [Indexed: 06/28/2024]
Abstract
Adenylyl cyclases (ACs) are a group of enzymes that convert adenosine-5'-triphosphate (ATP) to cyclic adenosine 3',5' monophosphate (cAMP), a vital and ubiquitous signalling molecule in cellular responses to hormones and neurotransmitters. There are nine transmembrane (tmAC) forms, which have been widely studied; however, the tenth, soluble AC (sAC) is less extensively characterised. The eye is one of the most metabolically active sites in the body, where sAC has been found in abundance, making it a target for novel therapeutics and biomarking. In the cornea, AC plays a role in endothelial cell function, which is vital in maintaining stromal dehydration, and therefore, clarity. In the retina, AC has been implicated in axon cell growth and survival. As these cells are irreversibly damaged in glaucoma and injury, this molecule may provide focus for future therapies. Another potential area for glaucoma management is the source of aqueous humour production, the ciliary body, where AC has also been identified. Furthering the understanding of lacrimal gland function is vital in managing dry eye disease, a common and debilitating condition. sAC has been linked to tear production and could serve as a therapeutic target. Overall, ACs are an exciting area of study in ocular health, offering multiple avenues for future medical therapies and diagnostics. This review paper explores the diverse roles of ACs in the eye and their potential as targets for innovative treatments.
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Affiliation(s)
- Polly Thompson
- West of England Eye Unit, Royal Devon University Healthcare NHS Foundation Trust, Exeter EX2 5DW, UK;
| | - Virginija Vilkelyte
- University of Exeter Medical School, St Luke’s Campus, University of Exeter, Exeter EX1 2HZ, UK
| | - Malgorzata Woronkowicz
- NDDH, Royal Devon University Healthcare NHS Foundation Trust, Barnstaple EX31 4JB, UK;
- Moorfields Eye Hospital NHS Foundation Trust, 162 City Road, London EC1V 2PD, UK
| | - Mitra Tavakoli
- University of Exeter Medical School, St Luke’s Campus, University of Exeter, Exeter EX1 2HZ, UK
| | - Piotr Skopinski
- Department of Ophthalmology, SPKSO Ophthalmic University Hospital, Medical University of Warsaw, 00-576 Warsaw, Poland
- Department of Histology and Embryology, Medical University of Warsaw, 02-004 Warsaw, Poland
| | - Harry Roberts
- West of England Eye Unit, Royal Devon University Healthcare NHS Foundation Trust, Exeter EX2 5DW, UK;
- University of Exeter Medical School, St Luke’s Campus, University of Exeter, Exeter EX1 2HZ, UK
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Feng J, Zhang Y. The potential benefits of polyphenols for corneal diseases. Biomed Pharmacother 2023; 169:115862. [PMID: 37979379 DOI: 10.1016/j.biopha.2023.115862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 10/30/2023] [Accepted: 11/05/2023] [Indexed: 11/20/2023] Open
Abstract
The cornea functions as the primary barrier of the ocular surface, regulating temperature and humidity while providing protection against oxidative stress, harmful stimuli and pathogenic microorganisms. Corneal diseases can affect the biomechanical and optical properties of the eye, resulting in visual impairment or even blindness. Due to their diverse origins and potent biological activities, plant secondary metabolites known as polyphenols offer potential advantages for treating corneal diseases owing to their anti-inflammatory, antioxidant, and antibacterial properties. Various polyphenols and their derivatives have demonstrated diverse mechanisms of action in vitro and in vivo, exhibiting efficacy against a range of corneal diseases including repair of tissue damage, treatment of keratitis, inhibition of neovascularization, alleviation of dry eye syndrome, among others. Therefore, this article presents a concise overview of corneal and related diseases, along with an update on the research progress of natural polyphenols in safeguarding corneal health. A more comprehensive understanding of natural polyphenols provides a novel perspective for secure treatment of corneal diseases.
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Affiliation(s)
- Jing Feng
- State Key Laboratory Cultivation Base, Shandong Provincial Key Laboratory of Ophthalmology, Eye Institute of Shandong First Medical University, Qingdao, China
| | - Yangyang Zhang
- State Key Laboratory Cultivation Base, Shandong Provincial Key Laboratory of Ophthalmology, Eye Institute of Shandong First Medical University, Qingdao, China.
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Treps L, Declercq M, Bousfia S, Carmeliet P, Witters P. Comparative meta-analysis of cystic fibrosis cell models suggests partial endothelial-to-mesenchymal transition. J Cyst Fibros 2021; 20:876-880. [PMID: 33858770 DOI: 10.1016/j.jcf.2021.03.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 03/05/2021] [Accepted: 03/17/2021] [Indexed: 12/12/2022]
Abstract
The mesenchymal conversion of epithelial cells (EMT) has been suggested as a potential contributor in cystic fibrosis (CF) disease progression. Endothelial cells (EndCs), the cells lining blood vessels, express functional CFTR and CFTR impairment promotes endothelial activation and dysfunction. However, if the mesenchymal switch also exists in CF EndCs remains uncharacterized. To understand whether the endothelial-to-mesenchymal transition (EndMT) could occur in CF, we have conducted a transcriptomic meta-analysis of primary CFTR-impaired and patient-derived EndCs, and further compared our results to data from CF epithelial cells (EpCs) where EMT has been demonstrated. As compared to EpCs, we show that CFTR-impaired EndCs display a limited signature of EndMT, and that expression of the mesenchymal inducer Twist1 remained unchanged. Nonetheless, the use of CFTR modulators reduced the expression of mesenchymal markers from CF patient-derived EndCs, suggesting an additional therapeutic added-value next to the known effect on CFTR ion transport.
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Affiliation(s)
- Lucas Treps
- Laboratory of Angiogenesis and Vascular Metabolism, Centre for Cancer Biology, VIB, Leuven, Belgium; Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology and Leuven Cancer Institute (LKI), KU Leuven, Leuven, Belgium; Université de Nantes, CNRS, INSERM, CRCINA, F-44000 Nantes, France.
| | - Mathias Declercq
- Laboratory of Angiogenesis and Vascular Metabolism, Centre for Cancer Biology, VIB, Leuven, Belgium; Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology and Leuven Cancer Institute (LKI), KU Leuven, Leuven, Belgium; Department of Development and Regeneration, CF Centre, Woman and Child, KU Leuven, Leuven, Belgium
| | - Siham Bousfia
- Laboratory of Angiogenesis and Vascular Metabolism, Centre for Cancer Biology, VIB, Leuven, Belgium; Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology and Leuven Cancer Institute (LKI), KU Leuven, Leuven, Belgium; Department of Development and Regeneration, CF Centre, Woman and Child, KU Leuven, Leuven, Belgium
| | - Peter Carmeliet
- Laboratory of Angiogenesis and Vascular Metabolism, Centre for Cancer Biology, VIB, Leuven, Belgium; Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology and Leuven Cancer Institute (LKI), KU Leuven, Leuven, Belgium
| | - Peter Witters
- Department of Development and Regeneration, CF Centre, Woman and Child, KU Leuven, Leuven, Belgium; Department of Paediatrics, University Hospitals Leuven, Leuven, Belgium; Centre of Metabolic Diseases, University Hospitals Leuven, Leuven, Belgium
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Giannakouras P, Kanakis M, Diamantea F, Tzetis M, Koutsandrea C, Papaconstantinou D, Georgalas I. Ophthalmologic manifestations of adult patients with cystic fibrosis. Eur J Ophthalmol 2021; 32:11206721211008780. [PMID: 33832348 DOI: 10.1177/11206721211008780] [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] [Indexed: 01/10/2023]
Abstract
INTRODUCTION Cystic fibrosis (CF) is the most common life-shortening recessive genetic disease in Caucasians, affecting primarily the lungs. The objective of our study was to investigate potential ophthalmologic involvement in adult patients with CF. METHODS Fifty adult patients with cystic fibrosis and 60 age- and sex-matched controls underwent complete ophthalmologic examination including tear-film Break-Up Time (BUT), Macular Thickness, and peripapillary Retinal Nerve Fiber Layer (pRNFL) thickness measurements using Spectral Domain-OCT. RESULTS CF patients had significantly lower nasal-inferior pRNFL thickness (median 82 IQR 67-102 vs 92.5 IQR 82-107, p = 0.005) and lower percentage of normal tear Break-Up Time (56.0% vs 96.7%, p = 0.001) than healthy controls. All CF patients with BUT <10 s were diagnosed with blepharitis at the time of our assessement. The subgroup of patients homozygous for the most common CF mutation, F508del, had lower nasal-inferior pRNFL thickness (p = 0.014) and lower percentage of normal tear Break-Up Time (p = 0.001) compared to the control group. Additional findings, present in the CF group only, were punctuate retinal hemorrhages (four patients), vessel tortuosity (four patients), snail-track degeneration, and retinal tufts (two patients without refractive error). There were no significant differences in visual acuity, refractive errors, gonioscopic findings, or intraocular pressure between the groups. CONCLUSIONS Our study is, to the best of our knowledge, the largest ophthalmologic study of patients with cystic fibrosis. We found that CF patients had significantly decreased inferior-quadrant peripapillary retinal nerve fiber layer thickness and decreased tear-film break-up time compared to controls. We highlight the importance of careful regular ophthalmologic assessment and follow-up of these patients.
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Affiliation(s)
- Panagiotis Giannakouras
- First Department of Ophthalmology, G. Gennimatas General Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Menelaos Kanakis
- Department of Ophthalmology, General Hospital of Patras, University of Patras, Rio, Greece
| | - Filia Diamantea
- Third Respiratory Medicine Department, Sismanogleio General Hospital, Marousi, Greece
| | - Maria Tzetis
- Department of Medical Genetics, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Chrysanthi Koutsandrea
- First Department of Ophthalmology, G. Gennimatas General Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Dimitrios Papaconstantinou
- First Department of Ophthalmology, G. Gennimatas General Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Ilias Georgalas
- First Department of Ophthalmology, G. Gennimatas General Hospital, National and Kapodistrian University of Athens, Athens, Greece
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Tóth-Molnár E, Ding C. New insight into lacrimal gland function: Role of the duct epithelium in tear secretion. Ocul Surf 2020; 18:595-603. [DOI: 10.1016/j.jtos.2020.07.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 06/21/2020] [Accepted: 07/07/2020] [Indexed: 02/08/2023]
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Sensing through Non-Sensing Ocular Ion Channels. Int J Mol Sci 2020; 21:ijms21186925. [PMID: 32967234 PMCID: PMC7554890 DOI: 10.3390/ijms21186925] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 09/17/2020] [Accepted: 09/18/2020] [Indexed: 12/12/2022] Open
Abstract
Ion channels are membrane-spanning integral proteins expressed in multiple organs, including the eye. In the eye, ion channels are involved in various physiological processes, like signal transmission and visual processing. A wide range of mutations have been reported in the corresponding genes and their interacting subunit coding genes, which contribute significantly to an array of blindness, termed ocular channelopathies. These mutations result in either a loss- or gain-of channel functions affecting the structure, assembly, trafficking, and localization of channel proteins. A dominant-negative effect is caused in a few channels formed by the assembly of several subunits that exist as homo- or heteromeric proteins. Here, we review the role of different mutations in switching a “sensing” ion channel to “non-sensing,” leading to ocular channelopathies like Leber’s congenital amaurosis 16 (LCA16), cone dystrophy, congenital stationary night blindness (CSNB), achromatopsia, bestrophinopathies, retinitis pigmentosa, etc. We also discuss the various in vitro and in vivo disease models available to investigate the impact of mutations on channel properties, to dissect the disease mechanism, and understand the pathophysiology. Innovating the potential pharmacological and therapeutic approaches and their efficient delivery to the eye for reversing a “non-sensing” channel to “sensing” would be life-changing.
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8
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Chen X, Lee S, Zhang T, Duan T, Pasricha ND, Schallhorn JM, Levin MH, Koprivica V, Verkman AS. Nanomolar Potency Aminophenyltriazine CFTR Activator Reverses Corneal Epithelial Injury in a Mouse Model of Dry Eye. J Ocul Pharmacol Ther 2020; 36:147-153. [PMID: 31934802 DOI: 10.1089/jop.2019.0087] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Purpose: Dry eye disorders are a major health care burden. We previously reported the identification of N-methyl-N-phenyl-6-(2,2,3,3-tetrafluoropropoxy)-1,3,5-triazine-2,4-diamine [cystic fibrosis transmembrane conductance regulator (CFTR)act-K267], which activated human wild-type CFTR chloride conductance with EC50 ∼ 30 nM. Here, we report in vivo evidence for CFTRact-K267 efficacy in an experimental mouse model of dry eye using a human compatible ophthalmic vehicle. Methods: CFTR activation in mice in vivo was demonstrated by ocular surface potential difference (OSPD) measurements. Ocular surface pharmacodynamics was measured in tear fluid samples obtained at different times after topical administration of CFTRact-K267. Dry eye was produced by lacrimal duct cautery (LDC) and corneal epithelial injury and was assessed by Lissamine green (LG) staining. Results: OSPD measurements demonstrated a hyperpolarization of -8.6 ± 3 mV (standard error of the mean, 5 mice) in response to CFTRact-K267 exposure in low chloride solution that was reversed by a CFTR inhibitor. Following single-dose topical administration of 2 nmol CFTRact-K267, tear fluid CFTRact-K267 concentration was >500 nM for more than 6 h. Following LDC, corneal surface epithelial injury, as assessed by LG staining, was substantially reversed in 10 of 12 eyes receiving 2 nmol CFTRact-K267 3 times daily starting on day 2, when marked epithelial injury had already occurred. Improvement was seen in 3 of 12 vehicle-treated eyes. Conclusion: These studies provide in vivo evidence in mice for the efficacy of a topical, human use compatible CFTRact-K267 formulation in stimulating chloride secretion and reversing corneal epithelial injury in dry eye.
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Affiliation(s)
- Xiaolan Chen
- Department of Medicine and Physiology and University of California, San Francisco, California.,Jiangsu Agri-Animal Husbandry Vocational College, Taizhou, China
| | - Sujin Lee
- Department of Medicine and Physiology and University of California, San Francisco, California
| | - Tianyi Zhang
- Department of Medicine and Physiology and University of California, San Francisco, California
| | - Tianying Duan
- Department of Medicine and Physiology and University of California, San Francisco, California
| | - Neel D Pasricha
- Department of Ophthalmology, University of California, San Francisco, California
| | - Julie M Schallhorn
- Department of Ophthalmology, University of California, San Francisco, California
| | - Marc H Levin
- Department of Ophthalmology, Palo Alto Medical Foundation, Palo Alto, California
| | - Vuk Koprivica
- Vanda Pharmaceuticals, Inc., Washington, District of Columbia
| | - Alan S Verkman
- Department of Medicine and Physiology and University of California, San Francisco, California
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Berczeli O, Vizvári E, Katona M, Török D, Szalay L, Rárosi F, Németh I, Rakonczay Z, Hegyi P, Ding C, Tóth-Molnár E. Novel Insight Into the Role of CFTR in Lacrimal Gland Duct Function in Mice. Invest Ophthalmol Vis Sci 2018; 59:54-62. [PMID: 29305607 PMCID: PMC5756044 DOI: 10.1167/iovs.17-22533] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Purpose The role of cystic fibrosis transmembrane conductance regulator (CFTR) in lacrimal gland (LG) function has only recently received some attention, mainly from our group. In the present study, we investigated the potential changes of LG pathology, tear secretion, ocular surface integrity, and fluid secretion in isolated LG ducts from CFTR knockout (KO) mice. Methods Tear production and ocular surface integrity were investigated in anesthetized wild-type (WT) and KO mice using cotton threads and fluorescein staining, respectively. Immunofluorescence was used to localize CFTR protein in the LGs. Ductal fluid secretions evoked by forskolin (10 μM); cell-permeable cAMP analogue (8-bromo cAMP, 100 μM); or carbachol (100 μM) were measured in isolated LG ducts using video-microscopy. Intracellular Ca2+ homeostasis underlying carbachol stimulation was investigated with microfluorometry. Results Significant decrease in tear secretion and impaired ocular surface integrity were observed in KO mice. Immunofluorescence demonstrated the predominant presence of CFTR protein in the apical membranes of the duct cells from WT mice. Continuous fluid secretion was evoked by forskolin and 8-bromo cAMP in LG ducts from WT mice, while no secretory response was observed in ducts from KO mice. Carbachol caused similar secretory responses in ducts from WT and KO animals without significant differences in cytosolic Ca2+ signaling. Conclusions Our results suggest the important role of CFTR in LG ductal secretion and in the maintenance of ocular surface integrity, suggesting that CFTR may be a promising target of novel therapeutic approaches in the treatment of dry eye.
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Affiliation(s)
- Orsolya Berczeli
- Department of Ophthalmology, University of Szeged, Szeged, Hungary
| | - Eszter Vizvári
- Department of Ophthalmology, University of Szeged, Szeged, Hungary
| | - Máté Katona
- 1st Department of Internal Medicine, University of Szeged, Szeged, Hungary
| | - Dénes Török
- Department of Anatomy, University of Szeged, Szeged, Hungary
| | - László Szalay
- Department of Ophthalmology, University of Szeged, Szeged, Hungary
| | - Ferenc Rárosi
- Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary
| | - István Németh
- Department of Dermatology and Allergology, University of Szeged, Szeged, Hungary
| | - Zoltán Rakonczay
- 1st Department of Internal Medicine, University of Szeged, Szeged, Hungary.,Department of Pathophysiology, University of Szeged, Szeged, Hungary
| | - Péter Hegyi
- Institute for Translational Medicine and First Department of Medicine, University of Pécs, Pécs, Hungary.,MTA-SZTE Translational Gastroenterology Research Group, Szeged, Hungary
| | - Chuanqing Ding
- Pharmacology & Pharmaceutical Sciences, Ophthalmology, University of Southern California, Los Angeles, California, United States
| | - Edit Tóth-Molnár
- Department of Ophthalmology, University of Szeged, Szeged, Hungary.,Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
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Yu D, Davis RM, Aita M, Burns KA, Clapp PW, Gilmore RC, Chua M, O'Neal WK, Schlegel R, Randell SH, C Boucher R. Characterization of Rat Meibomian Gland Ion and Fluid Transport. Invest Ophthalmol Vis Sci 2016; 57:2328-43. [PMID: 27127933 PMCID: PMC4855829 DOI: 10.1167/iovs.15-17945] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Purpose We establish novel primary rat meibomian gland (MG) cell culture systems and explore the ion transport activities of the rat MG. Methods Freshly excised rat MG tissues were characterized as follows: (1) mRNA expression of selected epithelial ion channels/transporters were measured by RT-PCR, (2) localization of epithelial sodium channel (ENaC) mRNAs was performed by in situ hybridization, and (3) protein expression and localization of βENaC, the Na+/K+/Cl− cotransporter (NKCC), and the Na+/K+ ATPase were evaluated by immunofluorescence. Primary isolated rat MG cells were cocultured with 3T3 feeder cells and a Rho-associated kinase (ROCK) inhibitor (Y-27632) for expansion. Passaged rat MG cells were cultured as planar sheets under air-liquid interface (ALI) conditions for gene expression and electrophysiologic studies. Passaged rat MG cells also were cultured in matrigel matrices to form spheroids, which were examined ultrastructurally by transmission electron microscopy (TEM) and functionally using swelling assays. Results Expression of multiple ion channel/transporter genes was detected in rat MG tissues. β-ENaC mRNA and protein were localized more to MG peripheral acinar cells than central acinar cells or ductular epithelial cells. Electrophysiologic studies of rat MG cell planar cultures demonstrated functional sodium, chloride, and potassium channels, and cotransporters activities. Transmission electron microscopic analyses of rat MG spheroids revealed highly differentiated MG cells with abundant lysosomal lamellar bodies. Rat MG spheroids culture-based measurements demonstrated active volume regulation by ion channels. Conclusions This study demonstrates the presence and function of ion channels and volume transport by rat MG. Two novel primary MG cell culture models that may be useful for MG research were established.
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Affiliation(s)
- Dongfang Yu
- Marsico Lung Institute/UNC Cystic Fibrosis Research Center School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
| | - Richard M Davis
- Department of Ophthalmology, The University of North Carolina, Chapel Hill, North Carolina, United States
| | - Megumi Aita
- Neuroscience Center, The University of North Carolina, Chapel Hill, North Carolina, United States
| | - Kimberlie A Burns
- Marsico Lung Institute/UNC Cystic Fibrosis Research Center School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
| | - Phillip W Clapp
- Marsico Lung Institute/UNC Cystic Fibrosis Research Center School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
| | - Rodney C Gilmore
- Marsico Lung Institute/UNC Cystic Fibrosis Research Center School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
| | - Michael Chua
- Marsico Lung Institute/UNC Cystic Fibrosis Research Center School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
| | - Wanda K O'Neal
- Marsico Lung Institute/UNC Cystic Fibrosis Research Center School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
| | - Richard Schlegel
- Department of Pathology, Georgetown University Medical School, Washington District of Columbia, United States
| | - Scott H Randell
- Marsico Lung Institute/UNC Cystic Fibrosis Research Center School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
| | - Richard C Boucher
- Marsico Lung Institute/UNC Cystic Fibrosis Research Center School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
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Li S, Kim E, Bonanno JA. Fluid transport by the cornea endothelium is dependent on buffering lactic acid efflux. Am J Physiol Cell Physiol 2016; 311:C116-26. [PMID: 27225657 PMCID: PMC4967133 DOI: 10.1152/ajpcell.00095.2016] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 05/17/2016] [Indexed: 11/22/2022]
Abstract
Maintenance of corneal hydration is dependent on the active transport properties of the corneal endothelium. We tested the hypothesis that lactic acid efflux, facilitated by buffering, is a component of the endothelial fluid pump. Rabbit corneas were perfused with bicarbonate-rich (BR) or bicarbonate-free (BF) Ringer of varying buffering power, while corneal thickness was measured. Perfusate was collected and analyzed for lactate efflux. In BF with no added HEPES, the maximal corneal swelling rate was 30.0 ± 4.1 μm/h compared with 5.2 ± 0.9 μm/h in BR. Corneal swelling decreased directly with [HEPES], such that with 60 mM HEPES corneas swelled at 7.5 ± 1.6 μm/h. Perfusate [lactate] increased directly with [HEPES]. Similarly, reducing the [HCO3 (-)] increased corneal swelling and decreased lactate efflux. Corneal swelling was inversely related to Ringer buffering power (β), whereas lactate efflux was directly related to β. Ouabain (100 μM) produced maximal swelling and reduction in lactate efflux, whereas carbonic anhydrase inhibition and an monocarboxylic acid transporter 1 inhibitor produced intermediate swelling and decreases in lactate efflux. Conversely, 10 μM adenosine reduced the swelling rate to 4.2 ± 0.8 μm/h and increased lactate efflux by 25%. We found a strong inverse relation between corneal swelling and lactate efflux (r = 0.98, P < 0.0001). Introducing lactate in the Ringer transiently increased corneal thickness, reaching a steady state (0 ± 0.6 μm/h) within 90 min. We conclude that corneal endothelial function does not have an absolute requirement for bicarbonate; rather it requires a perfusing solution with high buffering power. This facilitates lactic acid efflux, which is directly linked to water efflux, indicating that lactate flux is a component of the corneal endothelial pump.
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Affiliation(s)
- Shimin Li
- School of Optometry, Indiana University, Bloomington, Indiana
| | - Edward Kim
- School of Optometry, Indiana University, Bloomington, Indiana
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Peters W, Kusche-Vihrog K, Oberleithner H, Schillers H. Cystic fibrosis transmembrane conductance regulator is involved in polyphenol-induced swelling of the endothelial glycocalyx. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 2015; 11:1521-30. [PMID: 25881741 DOI: 10.1016/j.nano.2015.03.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 03/15/2015] [Accepted: 03/23/2015] [Indexed: 12/21/2022]
Abstract
UNLABELLED Previous studies show that polyphenol-rich compounds can induce a swelling of the endothelial glycocalyx (eGC). Our goal was to reveal the mechanism behind the eGC-swelling. As polyphenols are potent modulators of fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel, the hypothesis was tested whether polyphenol-induced increase in CFTR activity is responsible for the eGC-swelling. The impact of the polyphenols resveratrol, (-)-epicatechin, and quercetin on nanomechanics of living endothelial GM7373 cells was monitored by AFM-nanoindentation. The tested polyphenols lead to eGC-swelling with a simultaneous decrease in cortical stiffness. EGC-swelling, but not the change in cortical stiffness, was prevented by the inhibition of CFTR. Polyphenol-induced eGC-swelling could be mimicked by cytochalasin D, an actin-depolymerizing agent. Thus, in the vascular endothelium, polyphenols induce eGC-swelling by softening cortical actin and activating CFTR. Our findings imply that CFTR plays an important role in the maintenance of vascular homeostasis and may explain the vasoprotective properties of polyphenols. FROM THE CLINICAL EDITOR Many vascular problems clinically can be attributed to a dysregulation of endothelial glycocalyx (eGC). The underlying mechanism however remains unclear. In this article, the authors used nanoindentation and showed that polyphenols could swell the endothelial glycocalyx and alter its function. This investigative method can lead to further mechanistic studies of other molecular pathways.
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Affiliation(s)
- Wladimir Peters
- Institute of Physiology II, University of Münster, Münster, Germany
| | | | | | - Hermann Schillers
- Institute of Physiology II, University of Münster, Münster, Germany.
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Ivonnet P, Salathe M, Conner GE. Hydrogen peroxide stimulation of CFTR reveals an Epac-mediated, soluble AC-dependent cAMP amplification pathway common to GPCR signalling. Br J Pharmacol 2014; 172:173-84. [PMID: 25220136 DOI: 10.1111/bph.12934] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Revised: 08/27/2014] [Accepted: 09/03/2014] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND AND PURPOSE H2 O2 is widely understood to regulate intracellular signalling. In airway epithelia, H2 O2 stimulates anion secretion primarily by activating an autocrine PGE2 signalling pathway via EP4 and EP1 receptors to initiate cytic fibrosis transmembrane regulator (CFTR)-mediated Cl(-) secretion. This study investigated signalling downstream of the receptors activated by H2 O2 . EXPERIMENTAL APPROACH Anion secretion by differentiated bronchial epithelial cells was measured in Ussing chambers during stimulation with H2 O2 , an EP4 receptor agonist or β2 -adrenoceptor agonist in the presence and absence of inhibitors of ACs and downstream effectors. Intracellular calcium ([Ca(2+) ]I ) changes were followed by microscopy using fura-2-loaded cells and PKA activation followed by FRET microscopy. KEY RESULTS Transmembrane adenylyl cyclase (tmAC) and soluble AC (sAC) were both necessary for H2 O2 and EP4 receptor-mediated CFTR activation in bronchial epithelia. H2 O2 and EP4 receptor agonist stimulated tmAC to increase exchange protein activated by cAMP (Epac) activity that drives PLC activation to raise [Ca(2+) ]i via Ca(2+) store release (and not entry). Increased [Ca(2+) ]i led to sAC activation and further increases in CFTR activity. Stimulation of sAC did not depend on changes in [HCO3 (-) ]. Ca(2+) -activated apical KCa 1.1 channels and cAMP-activated basolateral KV 7.1 channels contributed to H2 O2 -stimulated anion currents. A similar Epac-mediated pathway was seen following β2 -adrenoceptor or forskolin stimulation. CONCLUSIONS AND IMPLICATIONS H2 O2 initiated a complex signalling cascade that used direct stimulation of tmACs by Gαs followed by Epac-mediated Ca(2+) crosstalk to activate sAC. The Epac-mediated Ca(2+) signal constituted a positive feedback loop that amplified CFTR anion secretion following stimulation of tmAC by a variety of stimuli.
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Affiliation(s)
- P Ivonnet
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, University of Miami, Miami, Florida, USA
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14
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Lee YS, Marmorstein LY, Marmorstein AD. Soluble adenylyl cyclase in the eye. Biochim Biophys Acta Mol Basis Dis 2014; 1842:2579-83. [PMID: 25108282 DOI: 10.1016/j.bbadis.2014.07.032] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 07/26/2014] [Accepted: 07/30/2014] [Indexed: 11/26/2022]
Abstract
Adenylyl cyclases (ACs) are a family of enzymes which convert ATP to cAMP, an essential intermediate in many signal transduction pathways. Of the 10 AC genes in man, 9 fall into the category of transmembrane ACs (tmACs), which associate with G-protein coupled receptors (GPCRs) and are activated by forskolin. The 10th AC, termed soluble AC (sAC) is neither activated by forskolin nor does it interact with GPCRs. Rather, sAC can be found in many compartments within the cell and is activated by bicarbonate. As such, sAC is considered a major sensor of bicarbonate in many tissues. The pathways involving sAC vary in different tissues and organ systems, and are as diverse as facilitating sperm capacitation and regulating pressure in the eye. The role of sAC in the eye has only recently begun to receive significant attention. Here we summarize what is known about the roles of sAC in the eye. This article is part of a Special Issue entitled: The role of soluble adenylyl cyclase in health and disease.
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Affiliation(s)
- Yong S Lee
- Department of Ophthalmology, Mayo Clinic, Rochester, MN 55902, USA
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15
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Yu D, Thelin WR, Rogers TD, Stutts MJ, Randell SH, Grubb BR, Boucher RC. Regional differences in rat conjunctival ion transport activities. Am J Physiol Cell Physiol 2012; 303:C767-80. [PMID: 22814399 PMCID: PMC3469597 DOI: 10.1152/ajpcell.00195.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Accepted: 07/18/2012] [Indexed: 12/26/2022]
Abstract
Active ion transport and coupled osmotic water flow are essential to maintain ocular surface health. We investigated regional differences in the ion transport activities of the rat conjunctivas and compared these activities with those of cornea and lacrimal gland. The epithelial sodium channel (ENaC), sodium/glucose cotransporter 1 (Slc5a1), transmembrane protein 16 (Tmem16a, b, f, and g), cystic fibrosis transmembrane conductance regulator (Cftr), and mucin (Muc4, 5ac, and 5b) mRNA expression was characterized by RT-PCR. ENaC proteins were measured by Western blot. Prespecified regions (palpebral, fornical, and bulbar) of freshly isolated conjunctival tissues and cell cultures were studied electrophysiologically with Ussing chambers. The transepithelial electrical potential difference (PD) of the ocular surface was also measured in vivo. The effect of amiloride and UTP on the tear volume was evaluated in lacrimal gland excised rats. All selected genes were detected but with different expression patterns. We detected αENaC protein in all tissues, βENaC in palpebral and fornical conjunctiva, and γENaC in all tissues except lacrimal glands. Electrophysiological studies of conjunctival tissues and cell cultures identified functional ENaC, SLC5A1, CFTR, and TMEM16. Fornical conjunctiva exhibited the most active ion transport under basal conditions amongst conjunctival regions. PD measurements confirmed functional ENaC-mediated Na(+) transport on the ocular surface. Amiloride and UTP increased tear volume in lacrimal gland excised rats. This study demonstrated that the different regions of the conjunctiva exhibited a spectrum of ion transport activities. Understanding the specific functions of distinct regions of the conjunctiva may foster a better understanding of the physiology maintaining hydration of the ocular surface.
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Affiliation(s)
- Dongfang Yu
- Cystic Fibrosis/Pulmonary Research and Treatment Center. Univ. of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA
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16
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Njie-Mbye YF, Opere CA, Chitnis M, Ohia SE. Hydrogen sulfide: role in ion channel and transporter modulation in the eye. Front Physiol 2012; 3:295. [PMID: 22934046 PMCID: PMC3429066 DOI: 10.3389/fphys.2012.00295] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 07/08/2012] [Indexed: 01/28/2023] Open
Abstract
Hydrogen sulfide (H2S), a colorless gas with a characteristic smell of rotten eggs, has been portrayed for decades as a toxic environmental pollutant. Since evidence of its basal production in mammalian tissues a decade ago, H2S has attracted substantial interest as a potential inorganic gaseous mediator with biological importance in cellular functions. Current research suggests that, next to its counterparts nitric oxide and carbon monoxide, H2S is an important multifunctional signaling molecule with pivotal regulatory roles in various physiological and pathophysiological processes as diverse as learning and memory, modulation of synaptic activities, cell survival, inflammation, and maintenance of vascular tone in the central nervous and cardiovascular systems. In contrast, there are few reports of a regulatory role of H2S in the eye. Accumulating reports on the pharmacological role of H2S in ocular tissues indicate the existence of a functional trans-sulfuration pathway and a potential physiological role for H2S as a gaseous neuromodulator in the eye. Thus, understanding the role of H2S in vision-related processes is imperative to our expanding knowledge of this molecule as a gaseous mediator in ocular tissues. This review aims to provide a comprehensive and current understanding of the potential role of H2S as a signaling molecule in the eye. This objective is achieved by discussing the involvement of H2S in the regulation of (1) ion channels such as calcium (L-type, T-type, and intracellular stores), potassium (KATP and small conductance channels) and chloride channels, (2) glutamate transporters such as EAAT1/GLAST and the L-cystine/glutamate antiporter. The role of H2S as an important mediator in cellular functions and physiological processes that are triggered by its interaction with ion channels/transporters in the eye will also be discussed.
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Affiliation(s)
- Ya F Njie-Mbye
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Texas Southern University Houston, TX, USA
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17
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Bonanno JA. Molecular mechanisms underlying the corneal endothelial pump. Exp Eye Res 2011; 95:2-7. [PMID: 21693119 DOI: 10.1016/j.exer.2011.06.004] [Citation(s) in RCA: 201] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 05/28/2011] [Accepted: 06/07/2011] [Indexed: 01/03/2023]
Abstract
The corneal endothelium is responsible for maintaining the hydration of the cornea. This is through a "Pump-Leak" mechanism where the active transport properties of the endothelium represent the "Pump" and the stromal swelling pressure represents the "Leak". For the "Pump", Na(+), K(+) ATPase activity and the presence of HCO(3)(-), Cl(-), and carbonic anhydrase activity are required. Several basolateral (stromal side) anion transporters, apical (facing the aqueous humor) ion channels and water channels have been identified that could support a model for ion secretion as the basis for the endothelial pump, however evidence of sustained anion fluxes, osmotic gradients or the need for water channels is lacking. This has prompted consideration of other models, such as Electro-osmosis, and consideration of metabolite flux as components of the endothelial pump. Although the conditions under which the "Pump" is supported are known, a complete model of the endothelial "Pump" has yet to emerge.
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Affiliation(s)
- Joseph A Bonanno
- Indiana University, School of Optometry, 800 E Atwater Avenue, Bloomington, IN 47405, USA.
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18
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Cao L, Zhang XD, Liu X, Chen TY, Zhao M. Chloride channels and transporters in human corneal epithelium. Exp Eye Res 2010; 90:771-9. [PMID: 20346358 DOI: 10.1016/j.exer.2010.03.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 03/02/2010] [Accepted: 03/17/2010] [Indexed: 01/14/2023]
Abstract
Transport of water and electrolytes is critical for corneal clarity. Recent studies indicate another important function of transport of ions and electrolytes - establishing wound electric fields that guide cell migration. We found chloride (Cl(-)) flux is a major component of the corneal wound electric current. In order to elucidate the mechanisms of Cl(-) transport, we studied Cl(-) channels and transporters in human corneal epithelial (HCE) cells. We tested a transformed human corneal epithelial cell line (tHCE), primary cultures of human corneal epithelial cells (pHCE), and human donor corneas. We first used RT-PCR to determine expression levels of mRNA of CLC (Cl(-) channels/transporters of CLC gene family) family members and CFTR (cystic fibrosis transmembrane conductance regulator) in HCE cells. We then confirmed protein expression and distribution of selected CLC family members and CFTR with Western blot and immunofluorescence confocal microscopy. Finally, Cl(-) currents were recorded with electrophysiological techniques. The mRNAs of CLC-2, CLC-3, CLC-4, CLC-5, CLC-6, and CFTR were detected in the HCE cell line. CLC-1 and CLC-7 were not detectable. Western blot and immunostaining confirmed protein expression and distribution of CLC-2, CLC-3, CLC-4, CLC-6 and CFTR in human corneal epithelium. CLC-2 preferentially labeled the apical and basal layers, while CLC-3 and CLC-4 labeled only the superficial layer. CLC-6 and CFTR labeling showed a unique gradient with strong staining in apical layers which gradually decreased towards the basal layers. Corneal endothelium was positive for CLC-2, CLC-3, CLC-4, CLC-6 and possibly CFTR. Human corneal epithelial cells demonstrated voltage dependent Cl(-) currents. HCE cells express functional Cl(-) channels and transporters. CLC-2, CLC-3, CLC-4, CLC-6, and CFTR had distinct expression patterns in human corneal epithelium. Those molecules and their distribution may play important roles in maintaining resting Cl(-) fluxes and in regulating Cl(-) flux at corneal wounds, which may be a major contributor to wound electrical signaling.
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Affiliation(s)
- Lin Cao
- Department of Dermatology, University of California, Davis, CA 95618, USA
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19
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Noe J, Petrusca D, Rush N, Deng P, VanDemark M, Berdyshev E, Gu Y, Smith P, Schweitzer K, Pilewsky J, Natarajan V, Xu Z, Obukhov AG, Petrache I. CFTR regulation of intracellular pH and ceramides is required for lung endothelial cell apoptosis. Am J Respir Cell Mol Biol 2009; 41:314-23. [PMID: 19168702 DOI: 10.1165/rcmb.2008-0264oc] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The functional significance of the expression of cystic fibrosis transmembrane regulator (CFTR) on endothelial cells has not yet been elucidated. Since CFTR has been implicated in the regulation of intracellular sphingolipid levels, which are important regulators of endothelial cell apoptosis in response to various insults, we investigated the role of CFTR in the apoptotic responses of lung endothelial cells. CFTR was detected as a functional chloride channel in primary lung endothelial cells isolated from both pulmonary arteries (human or mouse) and bronchial arteries (sheep). Both specific CFTR inhibition with 2-(phenylamino) benzoic acid diphenylamine-2-carboxylic acid, 5-[(4-carboxyphenyl)methylene]-2-thioxo-3-[(3-trifluoromethyl)phenyl-4-thiazolidinone (CFTR(inh)-172), or 5-nitro-2-(3-phenylpropylamino)benzoic acid and CFTR knockdown significantly attenuated endothelial cell apoptosis induced by staurosporine or H(2)O(2). CFTR(inh)-172 treatment prevented the increases in the ceramide:sphingosine-1 phosphate ratio induced by H(2)O(2) in lung endothelial cells. Replenishing endogenous ceramides via sphingomyelinase supplementation restored the susceptibility of CFTR-inhibited lung endothelial cells to H(2)O(2)-induced apoptosis. Similarly, the anti-apoptotic phenotype of CFTR-inhibited cells was reversed by lowering the intracellular pH, and was reproduced by alkalinization before H(2)O(2) challenge. TUNEL staining and active caspase-3 immunohistochemistry indicated that cellular apoptosis was decreased in lung explants from patients with cystic fibrosis compared with those with smoking-induced chronic obstructive lung disease, especially in the alveolar tissue and vascular endothelium. In conclusion, CFTR function is required for stress-induced apoptosis in lung endothelial cells by maintaining adequate intracellular acidification and ceramide activation. These results may have implications in the pathogenesis of cystic fibrosis, where aberrant endothelial cell death may dysregulate lung vascular homeostasis, contributing to abnormal angiogenesis and chronic inflammation.
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Affiliation(s)
- Julie Noe
- Section of Pulmonology and Critical Care, Department of Pediatrics, Indiana University, Indianapolis, Indiana 46202-5120, USA
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20
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Zhang Q, Hong M, Duan P, Pan Z, Ma J, You G. Organic anion transporter OAT1 undergoes constitutive and protein kinase C-regulated trafficking through a dynamin- and clathrin-dependent pathway. J Biol Chem 2008; 283:32570-9. [PMID: 18818201 PMCID: PMC2583290 DOI: 10.1074/jbc.m800298200] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Revised: 08/21/2008] [Indexed: 11/06/2022] Open
Abstract
Organic anion transporter 1 (OAT1) mediates the body disposition of a diverse array of environmental toxins and clinically important drugs. Therefore, understanding the regulation of this transporter has profound clinical significance. We previously demonstrate that OAT1 activity was down-regulated by activation of protein kinase C (PKC), kinetically revealed as a decrease in the maximum transport velocity V(max) without significant change in the substrate affinity K(m) of the transporter. In the current study, we showed that OAT1 constitutively internalized from and recycled back to the plasma membrane, and PKC activation accelerated OAT1 internalization without affecting OAT1 recycling. We further showed that treatment of OAT1-expressing cells with concanavalin A, depletion of K(+) from the cells, or transfection of dominant negative mutants of dynamin-2 or Eps15 into the cells, all of which block the clathrin-dependent endocytotic pathway, significantly blocked constitutive and PKC-regulated OAT1 internalization. We finally showed that OAT1 colocalized with transferrin, a marker for clathrin-dependent endocytosis, at the cell surface and in the EEA1-positive early endosomes. Together, our findings demonstrated for the first time that (i) OAT1 constitutively traffics between plasma membrane and recycling endosomes, (ii) PKC activation down-regulates OAT1 activity by altering already existent OAT1 trafficking, and (iii) OAT1 internalization occurs partly through a dynamin- and clathrin-dependent pathway.
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Affiliation(s)
- Qiang Zhang
- Department of Pharmaceutics, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
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21
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Hoffert JD, Fenton RA, Moeller HB, Simons B, Tchapyjnikov D, McDill BW, Yu MJ, Pisitkun T, Chen F, Knepper MA. Vasopressin-stimulated increase in phosphorylation at Ser269 potentiates plasma membrane retention of aquaporin-2. J Biol Chem 2008; 283:24617-27. [PMID: 18606813 DOI: 10.1074/jbc.m803074200] [Citation(s) in RCA: 198] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vasopressin controls water excretion through regulation of aquaporin-2 (AQP2) trafficking in renal collecting duct cells. Using mass spectrometry, we previously demonstrated four phosphorylated serines (Ser256, Ser261, Ser264, and Ser269) in the carboxyl-terminal tail of rat AQP2. Here, we used phospho-specific antibodies and protein mass spectrometry to investigate the roles of vasopressin and cyclic AMP in the regulation of phosphorylation at Ser269 and addressed the role of this site in AQP2 trafficking. The V2 receptor-specific vasopressin analog dDAVP increased Ser(P)269-AQP2 abundance more than 10-fold, but at a rate much slower than the corresponding increase in Ser256 phosphorylation. Vasopressin-mediated changes in phosphorylation at both sites were mimicked by cAMP addition and inhibited by protein kinase A (PKA) antagonists. In vitro kinase assays, however, demonstrated that PKA phosphorylates Ser256, but not Ser269. Phosphorylation of AQP2 at Ser269 did not occur when Ser256 was replaced by an unphosphorylatable amino acid, as seen in both S256L-AQP2 mutant mice and in Madin-Darby canine kidney cells expressing an S256A mutant, suggesting that Ser269 phosphorylation depends upon prior phosphorylation at Ser256. Immunogold electron microscopy localized Ser(P)269-AQP2 solely in the apical plasma membrane of rat collecting duct cells, in contrast to the other three phospho-forms (found in both apical plasma membrane and intracellular vesicles). Madin-Darby canine kidney cells expressing an S269D "phosphomimic" AQP2 mutant showed constitutive localization at the plasma membrane. The data support a model in which vasopressin-mediated phosphorylation of AQP2 at Ser269:(a) depends on prior PKA-mediated phosphorylation of Ser256 and (b) enhances apical plasma membrane retention of AQP2.
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Affiliation(s)
- Jason D Hoffert
- NHLBI, National Institutes of Health, Bethesda, Maryland 20892-1603, USA
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22
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Volumetric and ionic regulation during the in vitro development of a corneal endothelial barrier. Exp Eye Res 2008; 86:758-69. [PMID: 18384772 DOI: 10.1016/j.exer.2008.02.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Revised: 02/14/2008] [Accepted: 02/14/2008] [Indexed: 12/13/2022]
Abstract
Corneal endothelium is responsible for generating an ion flux between the corneal stroma and the anterior chamber of the eye that is necessary for the cornea to remain transparent. However, the ion transport regulatory mechanisms that develop during the formation of the endothelial barrier are not known. In this study, we determined the influence of cell confluence on cell volume and intracellular ionic content on the corneal endothelial cells of rabbits. Our results demonstrate that non-confluent endothelial cells display a hypertrophic volume increase, with higher intracellular contents of potassium and chlorine than those of confluent cells. In contrast, when cells reach confluence and the endothelial barrier forms, cell volume decreases and the intracellular contents of potassium and chlorine decrease. Our genetic analysis showed a higher expression of CFTR and CA2 genes in non-confluent cells, and of the gene KCNC3 in confluent cells. These results suggest that the normal ionic current that keeps the corneal stroma dehydrated and transparent is regulated by cell-cell contacts and endothelial cell confluence, and could explain why the loss of corneal endothelial cells is often associated with corneal edema and even blindness.
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23
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Li J, Allen KT, Sun XC, Cui M, Bonanno JA. Dependence of cAMP meditated increases in Cl- and HCO(3)- permeability on CFTR in bovine corneal endothelial cells. Exp Eye Res 2008; 86:684-90. [PMID: 18325495 DOI: 10.1016/j.exer.2008.01.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2007] [Revised: 01/18/2008] [Accepted: 01/22/2008] [Indexed: 11/28/2022]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is present on the apical membrane of corneal endothelial cells. Increasing intracellular [cAMP] with forskolin stimulates an NPPB and glibenclamide-inhibitable apical Cl(-) and HCO(3)(-) permeability [Sun, X.C., Bonanno, J.A., 2002. Expression, localization, and functional evaluation of CFTR in bovine corneal endothelial cells. Am. J. Physiol. Cell Physiol. 282, C673-C683]. To definitively determine that the increased permeability is dependent on CFTR, we used an siRNA knockdown approach. Apical Cl(-) and HCO(3)(-) permeability and steady-state HCO(3)(-) flux were measured in the presence or absence of forskolin using cultured bovine corneal endothelial cells that were transfected with CFTR siRNA or a scrambled sequence control. CFTR protein expression was reduced by approximately 80% in CFTR siRNA treated cultures. Forskolin (10 microM) increased apical chloride permeability by 7-fold, which was reduced to control level in siRNA treated cells. CFTR siRNA treatment had no effect on baseline apical chloride permeability. Apical HCO(3)(-) permeability was increased 2-fold by 10 microM forskolin, which was reduced to control level in siRNA treated cultures. Similarly, there was no effect on baseline apical HCO(3)(-) permeability by knocking down CFTR expression. The steady-state apical-basolateral pH gradient (DeltapH) at 4h in control cultures was increased approximately 2.5-fold by forskolin. In CFTR siRNA treated cells, the baseline DeltapH was similar to control, however forskolin did not have a significant effect. We conclude that forskolin induced increases in apical HCO(3)(-) permeability in bovine corneal endothelium requires CFTR. However, CFTR does not have a major role in determining baseline apical chloride or HCO(3)(-) permeability.
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Affiliation(s)
- Jinhua Li
- Indiana University, School of Optometry, Bloomington, IN 47405, USA
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24
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Lu HAJ, Sun TX, Matsuzaki T, Yi XH, Eswara J, Bouley R, McKee M, Brown D. Heat shock protein 70 interacts with aquaporin-2 and regulates its trafficking. J Biol Chem 2007; 282:28721-28732. [PMID: 17636261 DOI: 10.1074/jbc.m611101200] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The trafficking of aquaporin-2 (AQP2) involves multiple complex pathways, including regulated, cAMP-, and cGMP-mediated pathways, as well as a constitutive recycling pathway. Although several accessory proteins have been indirectly implicated in AQP2 recycling, the direct protein-protein interactions that regulate this process remain largely unknown. Using yeast two-hybrid screening of a human kidney cDNA library, we have identified the 70-kDa heat shock proteins as AQP2-interacting proteins. Interaction was confirmed by mass spectrometry of proteins pulled down from rat kidney papilla extract using a GST-AQP2 C-terminal fusion protein (GST-A2C) as a bait, by co-immunoprecipitation (IP) assays, and by direct binding assays using purified hsc70 and the GST-A2C. The direct interaction of AQP2 with hsc70 is partially inhibited by ATP, and the Ser-256 residue in the AQP2 C terminus is important for this direct interaction. Vasopressin stimulation in cells enhances the interaction of hsc70 with AQP2 in IP assays, and vasopressin stimulation in vivo induces an increased co-localization of hsc70 and AQP2 on the apical membrane of principal cells in rat kidney collecting ducts. Functional knockdown of hsc70 activity in AQP2 expressing cells results in membrane accumulation of AQP2 and reduced endocytosis of rhodamine-transferrin. Our data also show that AQP2 interacts with hsp70 in multiple in vitro binding assays. Finally, in addition to hsc70 and hsp70, AQP2 interacts with several other key components of the endocytotic machinery in co-IP assays, including clathrin, dynamin, and AP2. To summarize, we have identified the 70-kDa heat shock proteins as a AQP2 interactors and have shown for hsc70 that this interaction is involved in AQP2 trafficking.
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Affiliation(s)
- Hua A J Lu
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114.
| | - Tian-Xiao Sun
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Toshiyuki Matsuzaki
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Xian-Hua Yi
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Jairam Eswara
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Richard Bouley
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Mary McKee
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114
| | - Dennis Brown
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114.
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Zhang Y, Li J, Xie Q, Bonanno JA. Molecular expression and functional involvement of the bovine calcium-activated chloride channel 1 (bCLCA1) in apical HCO3- permeability of bovine corneal endothelium. Exp Eye Res 2006; 83:1215-24. [PMID: 16899243 PMCID: PMC3108034 DOI: 10.1016/j.exer.2006.06.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2006] [Revised: 06/14/2006] [Accepted: 06/26/2006] [Indexed: 10/24/2022]
Abstract
Corneal endothelium secretes HCO(3)(-) from basolateral (stroma) to apical (anterior chamber) compartments. Apical HCO(3)(-) permeability can be enhanced by increasing [Ca(2+)](i). We hypothesized that the bovine calcium-activated chloride channel 1 (bCLCA1), shown previously by PCR screening to be expressed in corneal endothelium, is involved in Ca(2+) activated apical HCO(3)(-) permeability. bCLCA1 expression in cultured bovine corneal endothelial cells (CBCEC) was examined by in situ hybridization analysis, immunoblotting, immunofluorescence and confocal microscopy. Rabbit polyclonal antibodies were generated using a 14 aa polypeptide (417-430) from the predicted sequence of bCLCA1. The small interference RNA (siRNA) knock down technique was used to evaluate the functional involvement of bCLCA1 in apical HCO(3)(-) permeability. In situ hybridization confirmed prominent bCLCA1-specific mRNA expression in CBCEC. bCLCA1 antiserum detected the heterologously expressed bCLCA1 in HEK293 cells and a 90kDa band in CBCEC, which was absent when using the pre-immune serum or antigen absorption of serum. Immunofluoresence staining with anti-bCLCA1 antibody and confocal microscopy indicates an apical membrane location in CBCEC. In CBCEC transfected with bCLCA1 specific siRNA, bCLCA1 expression was reduced by 80%, while transfection with siControl scrambled sequence had no effect. Increasing [Ca(i)(2+)] by application of ATPgammaS or cyclopiazonic acid (CPA) increased apical HCO(3)(-) permeability in siControl transfected CBCEC, while having no effect on apical HCO(3)(-) permeability in bCLCA1 specific siRNA transfected cells. Baseline HCO(3)(-) permeability, however, was not different between controls and siRNA treated cells. We conclude that the calcium-activated chloride channel (bCLCA1) is expressed in bovine corneal endothelial cells and can contribute to Ca(2+) dependent apical HCO(3)(-) permeability, but not resting permeability, across the corneal endothelium.
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Affiliation(s)
| | | | | | - Joseph A. Bonanno
- Corresponding author. Tel.: +1 812 856 5977; fax: +1 812 855 7045. (J.A. Bonanno)
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Levin MH, Verkman AS. Aquaporins and CFTR in ocular epithelial fluid transport. J Membr Biol 2006; 210:105-15. [PMID: 16868675 DOI: 10.1007/s00232-005-0849-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Indexed: 12/13/2022]
Abstract
Aquaporins (AQPs) and the cystic fibrosis transmembrane conductance regulator (CFTR) provide the molecular routes for transport of water and chloride, respectively, through many epithelial tissues. In ocular epithelia, fluid transport generally involves secondary active chloride transport, which creates the osmotic gradient to drive transepithelial water transport. This review is focused on the role of AQPs and CFTR in water and ion transport across corneal/conjunctival epithelia, corneal endothelium, ciliary epithelium, and retinal pigment epithelium. The potential relevance of water and chloride transport to common disorders of ocular fluid balance is also considered. Recent data suggest AQPs and CFTR as attractive targets for drug development for therapy of keratoconjunctivitis sicca, recurrent corneal erosions, corneal edema, glaucoma, retinal detachment, and retinal ischemia.
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Affiliation(s)
- M H Levin
- Department of Medicine, Cardiovascular Research Institute, Graduate Group in Biophysics, University of California, San Francisco, CA 94143-0521, USA
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Gorska MM, Cen O, Liang Q, Stafford SJ, Alam R. Differential regulation of interleukin 5-stimulated signaling pathways by dynamin. J Biol Chem 2006; 281:14429-39. [PMID: 16556602 DOI: 10.1074/jbc.m512718200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Through the yeast two-hybrid screen we have identified dynamin-2 as a molecule that interacts with the alpha subunit of the interleukin (IL) 5 receptor. Dynamin-2 is a GTPase that is critical for endocytosis. We have shown that dynamin-2 interacts with the IL-5 receptor-associated tyrosine kinases, Lyn and JAK2, in eosinophils. Tyrosine phosphorylation of dynamin is markedly enhanced upon IL-5 stimulation. The inhibition of tyrosine kinases results in complete abolition of ligand-induced receptor endocytosis. Inhibition of dynamin by a dominant-negative mutant or by small interfering RNA results in enhancement of IL-5-stimulated ERK1/2 signaling and cell proliferation. In contrast, the absence of a functional dynamin does not affect STAT5 or AKT phosphorylation or cell survival. Thus, we have identified specific functions for dynamin in the IL-5 signaling pathway and demonstrated its role in receptor endocytosis and termination of the ERK1/2 signaling pathway.
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Affiliation(s)
- Magdalena M Gorska
- Division of Allergy and Immunology, Department of Medicine, National Jewish Medical and Research Center, Denver, Colorado 80206, USA
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28
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Tan-Allen KY, Sun XC, Bonanno JA. Characterization of adenosine receptors in bovine corneal endothelium. Exp Eye Res 2005; 80:687-96. [PMID: 15862176 PMCID: PMC4113554 DOI: 10.1016/j.exer.2004.12.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Revised: 12/03/2004] [Accepted: 12/07/2004] [Indexed: 11/15/2022]
Abstract
Previous studies indicated that adenosine can increase [cAMP](i) and stimulate fluid transport by corneal endothelium. The purpose of this study was to determine which adenosine receptor subtype(s) are expressed and to examine their functional roles in modulating [cAMP](i), [Ca(2+)](i) and effects on Cl(-) permeability in corneal endothelium. We screened bovine corneal endothelium (BCE) for adenosine receptor subtypes by RT-PCR and immunoblotting, and examined the effects of pharmacological agents on adenosine stimulated Cl(-) transport, [cAMP](i) and [Ca(2+)](i). RT-PCR indicated the presence of A(1) and A(2b) adenosine receptors, while A(2a) and A(3) were negative. Western blot (WB) confirmed the presence of A(2b) ( approximately 50 kDa) and A(1) ( approximately 40 kDa) in fresh and cultured BCE. Ten micromolar adenosine increased [cAMP](i) by 2.7-fold over control and this was inhibited 66% by 10 microm alloxazine, a specific A(2b) blocker. A(1) activation with 1 micromN(6)-CPA (a specific A(1) agonist) or 100 nm adenosine decreased [cAMP](i) by 23 and 6%, respectively. Adenosine had no effect on [Ca(2+)](i) mobilization. Indirect immunofluorescence localized A(2b) receptors to the lateral membrane and A(1) to the apical surface in cultured BCE. Adenosine significantly increased apical Cl(-) permeability by 2.2 times and this effect was nearly abolished by DMPX (10 microm), a general A(2) blocker. Adenosine-induced membrane depolarization was also inhibited by 33% (n=6) in the presence of alloxazine. Bovine corneal endothelium expresses functional A(1) and A(2b) adenosine receptors. A(1), preferentially activated at <1 microm adenosine, acts to decrease [cAMP](i) and A(2b), activated at >1 microm adenosine, increase [cAMP](i).
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MESH Headings
- Adenosine/pharmacology
- Animals
- Blotting, Western
- Calcium/analysis
- Cattle
- Cell Membrane Permeability
- Cells, Cultured
- Chlorides/metabolism
- Cyclic AMP/analysis
- Endothelium, Corneal/chemistry
- Endothelium, Corneal/metabolism
- Flavins/pharmacology
- Fluorescent Antibody Technique, Indirect
- Membrane Potentials
- Purinergic P2 Receptor Antagonists
- RNA, Messenger/analysis
- Receptors, Purinergic/analysis
- Receptors, Purinergic/genetics
- Receptors, Purinergic P1/analysis
- Receptors, Purinergic P1/genetics
- Receptors, Purinergic P2/analysis
- Receptors, Purinergic P2/genetics
- Reverse Transcriptase Polymerase Chain Reaction
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Affiliation(s)
| | | | - Joseph A. Bonanno
- Corresponding author. Dr Joseph A. Bonanno, School of Optometry, Indiana University, 800 East Atwater Avenue, Bloomington, IN 47405, USA
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Beaulieu V, Da Silva N, Pastor-Soler N, Brown CR, Smith PJS, Brown D, Breton S. Modulation of the actin cytoskeleton via gelsolin regulates vacuolar H+-ATPase recycling. J Biol Chem 2004; 280:8452-63. [PMID: 15591047 DOI: 10.1074/jbc.m412750200] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The role of the actin cytoskeleton in regulating membrane protein trafficking is complex and depends on the cell type and protein being examined. Using the epididymis as a model system in which luminal acidification is crucial for sperm maturation and storage, we now report that modulation of the actin cytoskeleton by the calcium-activated actin-capping and -severing protein gelsolin plays a key role in regulating vacuolar H(+)-ATPase (V-ATPase) recycling. Epididymal clear cells contain abundant V-ATPase in their apical pole, and an increase in their cell-surface V-ATPase expression correlates with an increase in luminal proton secretion. We have shown that apical membrane accumulation of V-ATPase is triggered by an elevation in cAMP following activation of bicarbonate-regulated soluble adenylyl cyclase in response to alkaline luminal pH (Pastor-Soler, N., Beaulieu, V., Litvin, T. N., Da Silva, N., Chen, Y., Brown, D., Buck, J., Levin, L. R., and Breton, S. (2003) J. Biol. Chem. 278, 49523-49529). Here, we show that clear cells express high levels of gelsolin, indicating a potential role in the functional activity of these cells. When jasplakinolide was used to overcome the severing action of gelsolin by polymerizing actin, complete inhibition of the alkaline pH- and cAMP-induced apical membrane accumulation of V-ATPase was observed. Conversely, when gelsolin-mediated actin filament elongation was inhibited using a 10-residue peptide (PBP10) derived from the phosphatidylinositol 4,5-bisphosphate-binding region (phosphoinositide-binding domain 2) of gelsolin, significant V-ATPase apical membrane mobilization was induced, even at acidic luminal pH. In contrast, the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester) and the phospholipase C inhibitor U-73122 inhibited the alkaline pH-induced V-ATPase apical accumulation. Thus, maintenance of the actin cytoskeleton in a depolymerized state by gelsolin facilitates calcium-dependent apical accumulation of V-ATPase in response to luminal pH alkalinization. Gelsolin is present in other cell types that express the V-ATPase in their plasma membrane and recycling vesicles, including kidney intercalated cells and osteoclasts. Therefore, modulation of the actin cortex by this severing and capping protein may represent a common mechanism by which these cells regulate their rate of proton secretion.
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Affiliation(s)
- Valérie Beaulieu
- Program in Membrane Biology, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA
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Jiang B, Hattori N, Liu B, Nakayama Y, Kitagawa K, Inagaki C. Suppression of cell proliferation with induction of p21 by Cl(-) channel blockers in human leukemic cells. Eur J Pharmacol 2004; 488:27-34. [PMID: 15044032 DOI: 10.1016/j.ejphar.2004.02.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2003] [Revised: 01/27/2004] [Accepted: 02/06/2004] [Indexed: 10/26/2022]
Abstract
The existence of Cl(-) channels in lymphocytes and neutrophils has been increasingly recognized, but the biological functions are not yet clear. We examined the effects of Cl(-) channel blockers on the cell proliferation and the cell cycle of human leukemic cell lines. The growth of leukemic cells was suppressed most efficiently by NPPB (5-nitro-2-(3-phenylpropylamino) benzoic acid), partially by 9-AC (9-anthracenecarboxylic acid) and tamoxifen, but not by stilbene compounds. NPPB increased the G0/G1 population and induced the expression of p21, one of the critical molecules for G1/S checkpoint. Antisense oligonucleotide for a NPPB-sensitive and stilbene-insensitive Cl(-) channel, ClC-2, sufficiently suppressed the ClC-2 protein synthesis, but did not affect the growth of leukemic cells. These findings suggest that NPPB-sensitive and stilbene-insensitive Cl(-) channels other than ClC-2 play important roles in cell cycles and cell proliferation of human leukemic cells.
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Affiliation(s)
- Baohong Jiang
- Department of Pharmacology, Kansai Medical University, 10-15 Fumizono-cho, Moriguchi Osaka 570-8506, Japan
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Li J, Sun XC, Bonanno JA. Role of NBC1 in apical and basolateral HCO3- permeabilities and transendothelial HCO3- fluxes in bovine corneal endothelium. Am J Physiol Cell Physiol 2004; 288:C739-46. [PMID: 15548570 PMCID: PMC4096725 DOI: 10.1152/ajpcell.00405.2004] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Corneal transparency and hydration control are dependent on HCO(3)(-) transport properties of the corneal endothelium. Recent work (13) suggested the presence of an apical 1Na(+)-3HCO(3)(-) cotransporter (NBC1) in addition to a basolateral 1Na(+)-2HCO(3)(-) cotransporter. We examined whether the NBC1 cotransporter contributes significantly to basolateral or apical HCO(3)(-) permeability and whether the cotransporter participates in transendothelial net HCO(3)(-) flux in cultured bovine corneal endothelium. NBC1 protein expression was reduced using small interfering RNA (siRNA). Immunoblot analysis showed that 5-15 nM siRNA decreased NBC1 expression by 80-95%, 4 days posttransfection. Apical and basolateral HCO(3)(-) permeabilities were determined by measuring the rate of pH(i) change when HCO(3)(-) was removed from the bath under constant pH or constant CO(2) conditions. Using either protocol, we found that cultures treated with NBC1 siRNA had sixfold lower basolateral HCO(3)(-) permeability than untreated or siCONTROL siRNA-treated cells. Apical HCO(3)(-) permeability was unaffected by NBC1 siRNA treatment. Net non-steady-state HCO(3)(-) flux was 0.707 +/- 0.009 mM.min(-1).cm(2) in the basolateral-to-apical direction and increased to 1.74 +/- 0.15 when cells were stimulated with 2 muM forskolin. Treatment with 5 nM siRNA decreased basolateral-to-apical flux by 67%, whereas apical-to-basolateral flux was unaffected, significantly decreasing net HCO(3)(-) flux to 0.236 +/- 0.002. NBC1 siRNA treatment or 100 muM ouabain also eliminated steady-state HCO(3)(-) flux, as measured by apical compartment alkalinization. Collectively, reduced basolateral HCO(3)(-) permeability, basolateral-to-apical fluxes, and net HCO(3)(-) flux as a result of reduced expression of NBC1 indicate that NBC1 plays a key role in transendothelial HCO(3)(-) flux and is functional only at the basolateral membrane.
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Affiliation(s)
- Jinhua Li
- Indiana University School of Optometry, Bloomington, IN 47405, USA.
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32
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Sun XC, Cui M, Bonanno JA. [HCO3-]-regulated expression and activity of soluble adenylyl cyclase in corneal endothelial and Calu-3 cells. BMC PHYSIOLOGY 2004; 4:8. [PMID: 15117409 PMCID: PMC411047 DOI: 10.1186/1472-6793-4-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2003] [Accepted: 04/29/2004] [Indexed: 11/17/2022]
Abstract
BACKGROUND Bicarbonate activated Soluble Adenylyl Cyclase (sAC) is a unique cytoplasmic and nuclear signaling mechanism for the generation of cAMP. HCO3- activates sAC in bovine corneal endothelial cells (BCECs), increasing [cAMP] and stimulating PKA, leading to phosphorylation of the cystic fibrosis transmembrane-conductance regulator (CFTR) and increased apical Cl- permeability. Here, we examined whether HCO3- may also regulate the expression of sAC and thereby affect the production of cAMP upon activation by HCO3- and the stimulation of CFTR in BCECs. RESULTS RT-competitive PCR indicated that sAC mRNA expression in BCECs is dependent on [HCO3-] and incubation time in HCO3-. Immunoblots showed that 10 and 40 mM HCO3- increased sAC protein expression by 45% and 87%, respectively, relative to cells cultured in the absence of HCO3-. Furthermore, 40 mM HCO3- up-regulated sAC protein expression in Calu-3 cells by 93%. On the other hand, sAC expression in BCECs and Calu-3 cells was unaffected by changes in bath pH or osmolarity. Interestingly, BCECs pre-treated with10 microM adenosine or 10 microM forskolin, which increase cAMP levels, showed decreased sAC mRNA expression by 20% and 30%, respectively. Intracellular cAMP production by sAC paralleled the time and [HCO3-]-dependent expression of sAC. Bicarbonate-induced apical Cl- permeability increased by 78% (P < 0.01) in BCECs cultured in HCO3-. However for cells cultured in the absence of HCO3-, apical Cl- permeability increased by only 10.3% (P > 0.05). CONCLUSION HCO3- not only directly activates sAC, but also up-regulates the expression of sAC. These results suggest that active cellular uptake of HCO3- can contribute to the basal level of cellular cAMP in tissues that express sAC.
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Affiliation(s)
- Xing Cai Sun
- School of Optometry, Indiana University, 800 E. Atwater Ave, Bloomington, IN 47405 USA
| | - Miao Cui
- School of Optometry, Indiana University, 800 E. Atwater Ave, Bloomington, IN 47405 USA
| | - Joseph A Bonanno
- School of Optometry, Indiana University, 800 E. Atwater Ave, Bloomington, IN 47405 USA
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Diecke FPJ, Wen Q, Sanchez JM, Kuang K, Fischbarg J. Immunocytochemical localization of Na+-HCO3- cotransporters and carbonic anhydrase dependence of fluid transport in corneal endothelial cells. Am J Physiol Cell Physiol 2004; 286:C1434-42. [PMID: 14960417 DOI: 10.1152/ajpcell.00539.2003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In corneal endothelium, there is evidence for basolateral entry of HCO(3)(-) into corneal endothelial cells via Na(+)-HCO(3)(-) cotransporter (NBC) proteins and for net HCO(3)(-) flux from the basolateral to the apical side. However, how HCO(3)(-) exits the cells through the apical membrane is unclear. We determined that cultured corneal endothelial cells transport HCO(3)(-) similarly to fresh tissue. In addition, Cl(-) channel inhibitors decreased fluid transport by at most 16%, and inhibition of membrane-bound carbonic anhydrase IV by benzolamide or dextran-bound sulfonamide decreased fluid transport by at most 29%. Therefore, more than half of the fluid transport cannot be accounted for by anion transport through apical Cl(-) channels, CO(2) diffusion across the apical membrane, or a combination of these two mechanisms. However, immunocytochemistry using optical sectioning by confocal microscopy and cryosections revealed the presence of NBC transporters in both the basolateral and apical cell membranes of cultured bovine corneal endothelial cells and freshly isolated rabbit endothelia. This newly detected presence of an apical NBC transporter is consistent with its being the missing mechanism sought. We discuss discrepancies with other reports and provide a model that accounts for the experimental observations by assuming different stoichiometries of the NBC transport proteins at the basolateral and apical sides of the cells. Such functional differences might arise either from the expression of different isoforms or from regulatory factors affecting the stoichiometry of a single isoform.
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Sun XC, Zhai CB, Cui M, Chen Y, Levin LR, Buck J, Bonanno JA. HCO(3)(-)-dependent soluble adenylyl cyclase activates cystic fibrosis transmembrane conductance regulator in corneal endothelium. Am J Physiol Cell Physiol 2003; 284:C1114-22. [PMID: 12519749 PMCID: PMC4096724 DOI: 10.1152/ajpcell.00400.2002] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
cAMP-dependent activation of the cystic fibrosis transmembrane conductance regulator (CFTR) regulates fluid transport in many tissues. Secretion by the corneal endothelium is stimulated by cAMP and dependent on HCO(3)(-). We asked whether HCO(3)(-) can secondarily increase CFTR permeability in bovine corneal endothelial cells (BCEC) by activating soluble adenylyl cyclase (sAC). Immunofluorescence suggests that sAC is distributed throughout the cytoplasm. HCO(3)(-) (40 mM) increased cAMP concentration 42% in the presence of 50 microM rolipram (a phosphodiesterase 4 inhibitor), and a standard HCO(3)(-) Ringer solution (28.5 mM) increased apical Cl(-) permeability by 78% relative to HCO(3)(-)-free solution. The HCO(3)(-)-dependent increase in Cl(-) permeability was reduced 60% by 20 mM NaHSO(3) (a weak agonist of sAC). NaHSO(3) alone increased apical Cl(-) permeability by only 13%. The HCO(3)(-)-dependent increase in Cl(-) permeability was reduced 57% in the presence of 50 microM Rp-adenosine 3',5'-cyclic monophosphorothioate, and 86% by 50 microM 5-nitro-2-(3-phenylpropyl-amino)benzoic acid but unaffected by 200 microM apical H(2)DIDS. CFTR phosphorylation was increased 23, 150, and 32% by 20 mM HSO(3)(-), 28.5 mM HCO(3)(-), and 28.5 mM HCO(3)(-) + 20 mM HSO(3)(-), respectively. Activation of apical Cl(-) permeability by 5 microM genistein was increased synergistically by HCO(3)(-) over that due to genistein and HCO(3)(-) alone. We conclude that HCO(3)(-)-stimulated sAC is a form of autocrine signaling that contributes to baseline cAMP production, thereby affecting baseline CFTR activity in BCEC. This form of autocrine signaling may be important in tissues that express sAC and exhibit robust HCO(3)(-) influx (e.g., ocular ciliary epithelium, choroid plexus, and airway epithelium).
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Affiliation(s)
- Xing Cai Sun
- School of Optometry, Indiana University, Bloomington, Indiana 47405, USA
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