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Cai Y, Chen J, Sun H, Zhou T, Cai X, Fu Y. Crosstalk between TRPV1 and immune regulation in Fuchs endothelial corneal dystrophy. Clin Immunol 2023; 254:109701. [PMID: 37482117 DOI: 10.1016/j.clim.2023.109701] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 06/25/2023] [Accepted: 07/18/2023] [Indexed: 07/25/2023]
Abstract
Fuchs endothelial corneal dystrophy (FECD) is the leading indication for corneal transplantation worldwide. Our aim was to investigate the role of transient receptor potential vanilloid subtype 1 (TRPV1) and the associated immune regulation contributing to this pathological condition. Significant upregulation of TRPV1 was detected in the H2O2-induced in vitro FECD model. Based on gene expression microarray dataset GSE142538 and in vitro results, a comprehensive immune landscape was studied and a negative correlation was found between TRPV1 with different immune cells, especially regulatory T cells (Tregs). Functional analyses of the 313 TRPV1-related differentially expressed genes (DEGs) revealed the involvement of TRP-regulated calcium transport, as well as inflammatory and immune pathways. Four TRPV1-related core genes (MAPK14, GNB1, GNAQ, and ARRB2) were screened, validated by microarray dataset GSE112039 and the combined validation dataset E-GEAD-399 & 564, and verified by in vitro experiments. Our study suggested a potential crosstalk between TRPV1 and immune regulation contributing to FECD pathogenesis. The identified pivotal biomarkers and immune-related pathways provide a novel framework for future mechanistic and therapeutic studies of FECD.
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Affiliation(s)
- Yuchen Cai
- Department of Ophthalmology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, China
| | - Jin Chen
- Department of Ophthalmology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, China
| | - Hao Sun
- Department of Ophthalmology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, China
| | - Tianyi Zhou
- Department of Ophthalmology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, China
| | - Xueyao Cai
- Department of Plastic and Reconstructive Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
| | - Yao Fu
- Department of Ophthalmology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, China.
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Donau J, Luo H, Virta I, Skupin A, Pushina M, Loeffler J, Haertel FV, Das A, Kurth T, Gerlach M, Lindemann D, Reinach PS, Mergler S, Valtink M. TRPV4 Stimulation Level Regulates Ca2+-Dependent Control of Human Corneal Endothelial Cell Viability and Survival. MEMBRANES 2022; 12:membranes12030281. [PMID: 35323756 PMCID: PMC8952823 DOI: 10.3390/membranes12030281] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 02/18/2022] [Accepted: 02/24/2022] [Indexed: 02/04/2023]
Abstract
The functional contribution of transient receptor potential vanilloid 4 (TRPV4) expression in maintaining human corneal endothelial cells (HCEC) homeostasis is unclear. Accordingly, we determined the effects of TRPV4 gene and protein overexpression on responses modulating the viability and survival of HCEC. Q-PCR, Western blot, FACS analyses and fluorescence single-cell calcium imaging confirmed TRPV4 gene and protein overexpression in lentivirally transduced 12V4 cells derived from their parent HCEC-12 line. Although TRPV4 overexpression did not alter the baseline transendothelial electrical resistance (TEER), its cellular capacitance (Ccl) was larger than that in its parent. Scanning electron microscopy revealed that only the 12V4 cells developed densely packed villus-like protrusions. Stimulation of TRPV4 activity with GSK1016790A (GSK101, 10 µmol/L) induced larger Ca2+ transients in the 12V4 cells than those in the parental HCEC-12. One to ten nmol/L GSK101 decreased 12V4 viability, increased cell death rates and reduced the TEER, whereas 1 µmol/L GSK101 was required to induce similar effects in the HCEC-12. However, the TRPV4 channel blocker RN1734 (1 to 30 µmol/L) failed to alter HCEC-12 and 12V4 morphology, cell viability and metabolic activity. Taken together, TRPV4 overexpression altered both the HCEC morphology and markedly lowered the GSK101 dosages required to stimulate its channel activity.
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Affiliation(s)
- Jennifer Donau
- Institute of Anatomy, Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; (J.D.); (A.S.); (M.P.); (J.L.)
- Institute of Medical Microbiology and Virology, Faculty of Medicine, TU Dresden, 01307 Dresden, Germany;
| | - Huan Luo
- Klinik für Augenheilkunde, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 13353 Berlin, Germany; (H.L.); (I.V.)
| | - Iiris Virta
- Klinik für Augenheilkunde, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 13353 Berlin, Germany; (H.L.); (I.V.)
| | - Annett Skupin
- Institute of Anatomy, Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; (J.D.); (A.S.); (M.P.); (J.L.)
- Institute of Medical Microbiology and Virology, Faculty of Medicine, TU Dresden, 01307 Dresden, Germany;
| | - Margarita Pushina
- Institute of Anatomy, Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; (J.D.); (A.S.); (M.P.); (J.L.)
| | - Jana Loeffler
- Institute of Anatomy, Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; (J.D.); (A.S.); (M.P.); (J.L.)
| | - Frauke V. Haertel
- Institute of Physiology, Faculty of Medicine, University Giessen, 35392 Giessen, Germany;
- Institute of Physiology, Faculty of Medicine, TU Dresden, 01307 Dresden, Germany;
| | - Anupam Das
- Institute of Physiology, Faculty of Medicine, TU Dresden, 01307 Dresden, Germany;
| | - Thomas Kurth
- Center for Molecular and Cellular Bioengineering (CMCB), Technology Platform, TU Dresden, 01307 Dresden, Germany;
| | - Michael Gerlach
- Core Facility Cellular Imaging, Faculty of Medicine, TU Dresden, 01307 Dresden, Germany;
| | - Dirk Lindemann
- Institute of Medical Microbiology and Virology, Faculty of Medicine, TU Dresden, 01307 Dresden, Germany;
| | - Peter S. Reinach
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou 325027, China;
| | - Stefan Mergler
- Klinik für Augenheilkunde, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 13353 Berlin, Germany; (H.L.); (I.V.)
- Correspondence: (S.M.); (M.V.)
| | - Monika Valtink
- Institute of Anatomy, Faculty of Medicine, TU Dresden, 01307 Dresden, Germany; (J.D.); (A.S.); (M.P.); (J.L.)
- Equality and Diversity Unit, Faculty of Medicine, TU Dresden, 01307 Dresden, Germany
- Correspondence: (S.M.); (M.V.)
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Lee GH, Lee SY, Zheng C, Pham HT, Kim CY, Kim MY, Han EH, Hwang YP, Jeong HG. Effect of 3-caffeoyl, 4-dihydrocaffeoylquinic acid from Salicornia herbacea on endothelial nitric oxide synthase activation via calcium signaling pathway. Toxicol Res 2022; 38:355-364. [DOI: 10.1007/s43188-022-00121-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 12/26/2021] [Accepted: 01/06/2022] [Indexed: 11/29/2022] Open
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Amador-Muñoz D, Gutiérrez ÁM, Payán-Gómez C, Matheus LM. In silico and in vitro analysis of cation-activated potassium channels in human corneal endothelial cells. Exp Eye Res 2020; 197:108114. [PMID: 32561484 DOI: 10.1016/j.exer.2020.108114] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 06/02/2020] [Accepted: 06/07/2020] [Indexed: 12/31/2022]
Abstract
The corneal endothelium is the inner cell monolayer involved in the maintenance of corneal transparence by the generation of homeostatic dehydration. The glycosaminoglycans of the corneal stroma develop a continuous swelling pressure that should be counteracted by the corneal endothelial cells through active transport mechanisms to move the water to the anterior chamber. Protein transporters for sodium (Na+), potassium (K+), chloride (Cl-) and bicarbonate (HCO3-) are involved in this endothelial "pump function", however despite its physiological importance, the efflux mechanism is not completely understood. There is experimental evidence describing transendothelial diffusion of water in the absence of osmotic gradients. Therefore, it is important to get a deeper understanding of alternative models that drive the fluid transport across the endothelium such as the electrochemical gradients. Three transcriptomic datasets of the corneal endothelium were used in this study to analyze the expression of genes that encode proteins that participate in the transport and the reestablishment of the membrane potential across the semipermeable endothelium. Subsequently, the expression of the identified channels was validated in vitro both at mRNA and protein levels. The results of this study provide the first evidence of the expression of KCNN2, KCNN3 and KCNT2 genes in the corneal endothelium. Differences among the level of expression of KCNN2, KCNT2 and KCNN4 genes were found in a differentially expressed gene analysis of the dataset. Taken together these results underscore the potential importance of the ionic channels in the pathophysiology of corneal diseases. Moreover, we elucidate novel mechanisms that might be involved in the pivotal dehydrating function of the endothelium and in others physiologic functions of these cells using in silico pathways analysis.
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Affiliation(s)
- Diana Amador-Muñoz
- Neuroscience (NEUROS) Research Group, School of Medicine and Health Sciences, Universidad del Rosario, Carrera 24 No. 63 C 69, P.O 111221, Bogotá, Colombia.
| | - Ángela María Gutiérrez
- Escuela Superior de Oftalmología, Instituto Barraquer de América, Calle 100 No. 18 A 51, Bogotá, Colombia.
| | - César Payán-Gómez
- Department of Biology, Faculty of Natural Sciences, Universidad del Rosario, Carrera 24 No. 63 C 69, Bogotá, P.O 111221, Colombia.
| | - Luisa Marina Matheus
- Neuroscience (NEUROS) Research Group, School of Medicine and Health Sciences, Universidad del Rosario, Carrera 24 No. 63 C 69, P.O 111221, Bogotá, Colombia.
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Yoon CK, Yoon SY, Hwang JS, Shin YJ. O-GlcNAc Signaling Augmentation Protects Human Corneal Endothelial Cells from Oxidative Stress via AKT Pathway Activation. Curr Eye Res 2020; 45:556-562. [PMID: 31920129 DOI: 10.1080/02713683.2019.1686154] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Purpose: To investigate the effect of inhibitor of O-glycosylation on human corneal endothelial cells (HCECs) under oxidative stress.Methods: HCECs were cultured and treated with 10 mM tert-butyl hydroperoxide (tBHP) with or without PUGNAc, a known inhibitor of OGA. Cell viability was assessed. Mitochondrial membrane potential (ΔΨm) was measured. Intracellular Ca2+ levels and mitochondrial Ca2+ levels were measured. Intracellular reactive oxygen species formation was measured. Levels of O-linked β-N-acetylglucosamine (O-GlcNAc), AKT, and pAKT were evaluated by Western blotting.Results: O-GlcNAc augmentation by PUGNAc increased cell viability, attenuated the loss of ΔΨm, and intracellular ROS against tBHP-induced oxidative stress (p < .05). O-GlcNAc augmentation reduced tBHP-induced mitochondrial calcium overload (p < .05) while it did not have any effect on intracellular calcium overload with tBHP. Furthermore, AKT signaling was activated in the cells with O-GlcNAc augmentation.Conclusions: O-GlcNAc signaling augmentation protects HCECs from oxidative stress via activation of AKT pathways.
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Affiliation(s)
- Chang Ki Yoon
- Department of Ophthalmology, Hallym University College of Medicine, Seoul, Republic of Korea
| | - Sam Young Yoon
- Department of Ophthalmology, Hallym University College of Medicine, Seoul, Republic of Korea
| | - Jin Sun Hwang
- Department of Ophthalmology, Hallym University College of Medicine, Seoul, Republic of Korea
| | - Young Joo Shin
- Department of Ophthalmology, Hallym University College of Medicine, Seoul, Republic of Korea
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Lafreniere J, Kelly M. Potential for endocannabinoid system modulation in ocular pain and inflammation: filling the gaps in current pharmacological options. Neuronal Signal 2018; 2:NS20170144. [PMID: 32714590 PMCID: PMC7373237 DOI: 10.1042/ns20170144] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 10/18/2018] [Accepted: 10/19/2018] [Indexed: 02/06/2023] Open
Abstract
Challenges in the management of ocular pain are an underappreciated topic. Currently available therapeutics lack both efficacy and clear guidelines for their use, with many also possessing unacceptable side effects. Promising novel agents would offer analgesic, anti-inflammatory, and possibly neuroprotective actions; have favorable ocular safety profiles; and show potential in managing neuropathic pain. Growing evidence supports a link between the endocannabinoid system (ECS) and a range of physiological and disease processes, notably those involving inflammation and pain. Both preclinical and clinical data suggest analgesic and anti-inflammatory actions of cannabinoids and ECS-modifying drugs in chronic pain conditions, including those of neuropathic origin. This review will examine existing evidence for the anatomical and physiological basis of ocular pain, specifically, ocular surface disease and the development of chronic ocular pain. The mechanism of action, efficacy, and limitations of currently available treatments will be discussed, and current knowledge related to ECS-modulation of ocular pain and inflammatory disease will be summarized. A perspective will be provided on the future directions of ECS research in terms of developing cannabinoid therapeutics for ocular pain.
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Affiliation(s)
| | - Melanie E.M. Kelly
- Department of Pharmacology, Dalhousie University, Halifax, NS, Canada
- Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, NS, Canada
- Department of Anesthesia, Pain Management and Perioperative Medicine, Dalhousie University, Halifax, NS, Canada
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Melanaphy D, Johnson CD, Kustov MV, Watson CA, Borysova L, Burdyga TV, Zholos AV. Ion channel mechanisms of rat tail artery contraction-relaxation by menthol involving, respectively, TRPM8 activation and L-type Ca2+ channel inhibition. Am J Physiol Heart Circ Physiol 2016; 311:H1416-H1430. [PMID: 27765744 DOI: 10.1152/ajpheart.00222.2015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 09/13/2016] [Indexed: 11/22/2022]
Abstract
Transient receptor potential melastatin 8 (TRPM8) is the principal cold and menthol receptor channel. Characterized primarily for its cold-sensing role in sensory neurons, it is expressed and functional in several nonneuronal tissues, including vasculature. We previously demonstrated that menthol causes variable mechanical responses (vasoconstriction, vasodilatation, or biphasic reactions) in isolated arteries, depending on vascular tone. Here we aimed to dissect the specific ion channel mechanisms and corresponding Ca2+ signaling pathways underlying such complex responses to menthol and other TRPM8 ligands in rat tail artery myocytes using patch-clamp electrophysiology, confocal Ca2+ imaging, and ratiometric Ca2+ recording. Menthol (300 μM, a concentration typically used to induce TRPM8 currents) strongly inhibited L-type Ca2+ channel current (L-ICa) in isolated myocytes, especially its sustained component, most relevant for depolarization-induced vasoconstriction. In contraction studies, with nifedipine present (10 μM) to abolish L-ICa contribution to phenylephrine (PE)-induced vasoconstrictions of vascular rings, a marked increase in tone was observed with menthol, similar to resting (i.e., without α-adrenoceptor stimulation by PE) conditions, when L-type channels were mostly deactivated. Menthol-induced increases in PE-induced vasoconstrictions could be inhibited both by the TRPM8 antagonist AMTB (thus confirming the specific role of TRPM8) and by cyclopiazonic acid treatment to deplete Ca2+ stores, pointing to a major contribution of Ca2+ release from the sarcoplasmic reticulum in these contractile responses. Immunocytochemical analysis has indeed revealed colocalization of TRPM8 and InsP3 receptors. Moreover, menthol Ca2+ responses, which were somewhat reduced under Ca2+-free conditions, were strongly reduced by cyclopiazonic acid treatment to deplete Ca2+ store, whereas caffeine-induced Ca2+ responses were blunted in the presence of menthol. Finally, two other common TRPM8 agonists, WS-12 and icilin, also inhibited L-ICa With respect to L-ICa inhibition, WS-12 is the most selective agonist. It augmented PE-induced contractions, whereas any secondary phase of vasorelaxation (as with menthol) was completely lacking. Thus TRPM8 channels are functionally active in rat tail artery myocytes and play a distinct direct stimulatory role in control of vascular tone. However, indirect effects of TRPM8 agonists, which are unrelated to TRPM8, are mediated by inhibition of L-type Ca2+ channels and largely obscure TRPM8-mediated vasoconstriction. These findings will promote our understanding of the vascular TRPM8 role, especially the well-known hypotensive effect of menthol, and may also have certain translational implications (e.g., in cardiovascular surgery, organ storage, transplantation, and Raynaud's phenomenon).
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Affiliation(s)
- Donal Melanaphy
- Center for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, The Queen's University of Belfast, Belfast, United Kingdom
| | - Christopher D Johnson
- Centre for Biomedical Sciences Education, School of Medicine, Dentistry and Biomedical Sciences, The Queen's University of Belfast, Belfast, United Kingdom;
| | - Maxim V Kustov
- A. A. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kiev, Ukraine
| | - Conall A Watson
- Centre for Biomedical Sciences Education, School of Medicine, Dentistry and Biomedical Sciences, The Queen's University of Belfast, Belfast, United Kingdom
| | - Lyudmyla Borysova
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom; and
| | - Theodor V Burdyga
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom; and
| | - Alexander V Zholos
- Center for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, The Queen's University of Belfast, Belfast, United Kingdom.,A. A. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kiev, Ukraine.,Department of Biophysics, Institute of Biology, Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
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Reinach PS, Mergler S, Okada Y, Saika S. Ocular transient receptor potential channel function in health and disease. BMC Ophthalmol 2015; 15 Suppl 1:153. [PMID: 26818117 PMCID: PMC4895786 DOI: 10.1186/s12886-015-0135-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Transient receptor potential (TRP) channels sense and transduce environmental stimuli into Ca(2+) transients that in turn induce responses essential for cell function and adaptation. These non-selective channels with variable Ca(2+) selectivity are grouped into seven different subfamilies containing 28 subtypes based on differences in amino acid sequence homology. Many of these subtypes are expressed in the eye on both neuronal and non-neuronal cells where they affect a host of stress-induced regulatory responses essential for normal vision maintenance. This article reviews our current knowledge about the expression, function and regulation of TRPs in different eye tissues. We also describe how under certain conditions TRP activation can induce responses that are maladaptive to ocular function. Furthermore, the possibility of an association between TRP mutations and disease is considered. These findings contribute to evidence suggesting that drug targeting TRP channels may be of therapeutic benefit in a clinical setting. We point out issues that must be more extensively addressed before it will be possible to decide with certainty that this is a realistic endeavor. Another possible upshot of future studies is that disease process progression can be better evaluated by profiling changes in tissue specific functional TRP subtype activity as well as their gene and protein expression.
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Affiliation(s)
- Peter S Reinach
- Department of Ophthalmology and Optometry, Wenzhou Medical University, 270 Xuejuan Road, Wenzhou, Zhejiang, 325027, P. R. China.
| | - Stefan Mergler
- Department of Ophthalmology, Charité-University Medicine Berlin, Campus Virchow-Clinic, Augustenburger Platz 1, 13353, Berlin, Germany.
| | - Yuka Okada
- Department of Ophthalmology, Wakayama Medical University School of Medicine, Wakayama, Japan.
| | - Shizuya Saika
- Department of Ophthalmology, Wakayama Medical University School of Medicine, Wakayama, Japan.
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Reinach PS, Chen W, Mergler S. Polymodal roles of transient receptor potential channels in the control of ocular function. EYE AND VISION 2015; 2:5. [PMID: 26605361 PMCID: PMC4655450 DOI: 10.1186/s40662-015-0016-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 02/15/2015] [Indexed: 12/05/2022]
Abstract
Maintenance of intracellular Ca2+ levels at orders of magnitude below those in the extracellular environment is a requisite for preserving cell viability. Membrane channels contribute to such control through modulating their time-dependent opening and closing behaviour. Such regulation requires Ca2+ to serve as a second messenger mediating receptor control of numerous life-sustaining responses. Transient receptor potential (TRP) channels signal transduce a wide variety of different sensory stimuli to induce responses modulating cellular function. These channels are non-selective cation channels with variable Ca2+ selectivity having extensive sequence homology. They constitute a superfamily made up of 28 different members that are subdivided into 7 different subfamilies based on differences in sequence homology. Some of these TRP channel isotypes are expressed in the eye and localized to both neuronal and non-neuronal cell membranes. Their activation generates intracellular Ca2+ transients and other downstream-linked signalling events that affect numerous responses required for visual function. As there is an association between changes in functional TRP expression in various ocular diseases, there are efforts underway to determine if these channels can be used as drug targets to reverse declines in ocular function. We review here our current knowledge about the expression, function and regulation of TRPs in different eye tissues in health and disease. Furthermore, some of the remaining hurdles are described to developing safe and efficacious TRP channel modulators for use in a clinical setting.
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Affiliation(s)
- Peter S Reinach
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang 325027 P.R. China
| | - Weiwei Chen
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang 325027 P.R. China
| | - Stefan Mergler
- Charité-Universitätsmedizin Berlin, Campus Virchow-Klinikum, Klinik für Augenheilkunde, Augustenburger Platz 1, D-13353 Berlin, Germany
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Mergler S, Valtink M, Takayoshi S, Okada Y, Miyajima M, Saika S, Reinach PS. Temperature-sensitive transient receptor potential channels in corneal tissue layers and cells. Ophthalmic Res 2014; 52:151-9. [PMID: 25301091 DOI: 10.1159/000365334] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 06/16/2014] [Indexed: 11/19/2022]
Abstract
We here provide a brief summary of the characteristics of transient receptor potential channels (TRPs) identified in corneal tissue layers and cells. In general, TRPs are nonselective cation channels which are Ca(2+) permeable. Most TRPs serve as thermosensitive molecular sensors (thermo-TRPs). Based on their functional importance, the possibilities are described for drug-targeting TRP activity in a clinical setting. TRPs are expressed in various tissues of the eye including both human corneal epithelial and endothelial layers as well as stromal fibroblasts and stromal nerve fibers. TRP vanilloid type 1 (TRPV1) heat receptor, also known as capsaicin receptor, along with TRP melastatin type 8 (TRPM8) cold receptor, which is also known as menthol receptor, are prototypes of the thermo-TRP family. The TRPV1 functional channel is the most investigated TRP channel in these tissues, owing to its contribution to maintaining tissue homeostasis as well as eliciting wound healing responses to injury. Other thermo-TRP family members identified in these tissues are TRPV2, 3 and 4. Finally, there is the TRP ankyrin type 1 (TRPA1) cold receptor. All of these thermo-TRPs can be activated within specific temperature ranges and transduce such inputs into chemical and electrical signals. Although several recent studies have begun to unravel complex roles for thermo-TRPs such as TRPV1 in corneal layers and resident cells, additional studies are needed to further elucidate their roles in health and disease.
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Affiliation(s)
- Stefan Mergler
- Department of Ophthalmology, Charité - Universitätsmedizin Berlin, Berlin, Germany
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Mergler S, Mertens C, Valtink M, Reinach PS, Székely VC, Slavi N, Garreis F, Abdelmessih S, Türker E, Fels G, Pleyer U. Functional significance of thermosensitive transient receptor potential melastatin channel 8 (TRPM8) expression in immortalized human corneal endothelial cells. Exp Eye Res 2013; 116:337-49. [PMID: 24135298 DOI: 10.1016/j.exer.2013.10.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2013] [Revised: 08/17/2013] [Accepted: 10/03/2013] [Indexed: 11/18/2022]
Abstract
Human corneal endothelial cells (HCEC) maintain appropriate tissue hydration and transparency by eliciting net ion transport coupled to fluid egress from the stroma into the anterior chamber. Such activity offsets tissue swelling caused by stromal imbibition of fluid. As corneal endothelial (HCE) transport function is modulated by temperature changes, we probed for thermosensitive transient receptor potential melastatin 8 (TRPM8) functional activity in immortalized human corneal endothelial cells (HCEC-12) and freshly isolated human corneal endothelial cells (HCEC) as a control. This channel is either activated upon lowering to 28 °C or by menthol, eucalyptol and icilin. RT-PCR and quantitative real-time PCR (qPCR) verified TRPM8 gene expression. Ca(2+) transients induced by either menthol (500 μmol/l), eucalyptol (3 mmol/l), or icilin (2-60 μmol/l) were identified using cell fluorescence imaging. The TRP channel blocker lanthanum III chloride (La(3+), 100 μmol/l) as well as the TRPM8 blockers BCTC (10 μmol/l) and capsazepine (CPZ, 10 μmol/l) suppressed icilin-induced Ca(2+) increases. In and outward currents induced by application of menthol (500 μmol/l) or icilin (50 μmol/l) were detected using the planar patch-clamp technique. A thermal transition from room temperature to ≈ 18 °C led to Ca(2+) increases that were inhibited by a TRPM8 blocker BCTC (10 μmol/l). Other thermosensitive TRP pathways whose heterogeneous Ca(2+) response patterns are suggestive of other Ca(2+) handling pathways were also detected upon strong cooling (≈10 °C). Taken together, functional TRPM8 expression in HCEC-12 and freshly dissociated HCEC suggests that HCE function can adapt to thermal variations through activation of this channel subtype.
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Affiliation(s)
- Stefan Mergler
- Charité - Universitätsmedizin Berlin, Campus Virchow-Clinic, Department of Ophthalmology, Augustenburger Platz 1, 13353 Berlin, Germany.
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Mergler S, Valtink M, Taetz K, Sahlmüller M, Fels G, Reinach PS, Engelmann K, Pleyer U. Characterization of transient receptor potential vanilloid channel 4 (TRPV4) in human corneal endothelial cells. Exp Eye Res 2011; 93:710-9. [DOI: 10.1016/j.exer.2011.09.021] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 08/29/2011] [Accepted: 09/07/2011] [Indexed: 11/26/2022]
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Mergler S, Garreis F, Sahlmüller M, Reinach PS, Paulsen F, Pleyer U. Thermosensitive transient receptor potential channels in human corneal epithelial cells. J Cell Physiol 2011; 226:1828-42. [PMID: 21506114 DOI: 10.1002/jcp.22514] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Thermosensitive transient receptor potential (TRP) proteins such as TRPV1-TRPV4 are all heat-activated non-selective cation channels that are modestly permeable to Ca(2+). TRPV1, TRPV3, and TRPV4 functional expression were previously identified in human corneal epithelial cells (HCEC). However, the membrane currents were not described underlying their activation by either selective agonists or thermal variation. This study characterized the membrane currents and [Ca(2+)](i) transients induced by thermal and agonist TRPV1 and 4 stimulation. TRPV1 and 4 expressions were confirmed by RT-PCR and TRPV2 transcripts were also detected. In fura2-loaded HCEC, a TRPV1-3 selective agonist, 100 µM 2-aminoethoxydiphenyl borate (2-APB), induced intracellular Ca(2+) transients and an increase in non-selective cation outward currents that were suppressed by ruthenium-red (RuR) (10-20 µM), a non-selective TRPV channel blocker. These changes were also elicited by rises in ambient temperature from 25 to over 40 °C. RuR (5 µM) and a selective TRPV1 channel blocker capsazepine CPZ (10 µM) or another related blocker, lanthanum chloride (La(3+)) (100 µM) suppressed these temperature-induced Ca(2+) increases. Planar patch-clamp technique was used to characterize the currents underlying Ca(2+) transients. Increasing the temperature to over 40 °C induced reversible rises in non-selective cation currents. Moreover, a hypotonic challenge (25%) increased non-selective cation currents confirming TRPV4 activity. We conclude that HCEC possess in addition to thermosensitive TRPV3 activity TRPV1, TRPV2, and TRPV4 activity. Their activation confers temperature sensitivity at the ocular surface, which may protect the cornea against such stress.
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Affiliation(s)
- Stefan Mergler
- Department of Ophthalmology, Campus Virchow-Clinic, Charité - Universitätsmedizin Berlin, Berlin, Germany.
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14
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TRPV channels mediate temperature-sensing in human corneal endothelial cells. Exp Eye Res 2010; 90:758-70. [DOI: 10.1016/j.exer.2010.03.010] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2009] [Revised: 02/15/2010] [Accepted: 03/16/2010] [Indexed: 02/08/2023]
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15
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Capó-Aponte JE, Wang Z, Bildin VN, Iserovich P, Pan Z, Zhang F, Pokorny KS, Reinach PS. Functional and molecular characterization of multiple K-Cl cotransporter isoforms in corneal epithelial cells. Exp Eye Res 2007; 84:1090-103. [PMID: 17418819 PMCID: PMC2696115 DOI: 10.1016/j.exer.2007.02.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2006] [Revised: 12/19/2006] [Accepted: 02/06/2007] [Indexed: 11/20/2022]
Abstract
The dependence of regulatory volume decrease (RVD) activity on potassium-chloride cotransporter (KCC) isoform expression was characterized in corneal epithelial cells (CEC). During exposure to a 50% hypotonic challenge, the RVD response was larger in SV40-immortalized human CEC (HCEC) than in SV40-immortalized rabbit CEC (RCEC). A KCC inhibitor-[(dihydroindenyl)oxy] alkanoic acid (DIOA)-blocked RVD more in HCEC than RCEC. Under isotonic conditions, N-ethylmaleimide (NEM) produced KCC activation and transient cell shrinkage. Both of these changes were greater in HCEC than in RCEC. Immunoblot analysis of HCEC, RCEC, primary human CEC (pHCEC), and primary bovine CEC (BCEC) plasma membrane enriched fractions revealed KCC1, KCC3, and KCC4 isoform expression, whereas KCC2 was undetectable. During a hypotonic challenge, KCC1 membrane content increased more rapidly in HCEC than in RCEC. Such a challenge induced a larger increase and more transient p44/42MAPK activation in HCEC than RCEC. On the other hand, HCEC and RCEC p38MAPK phosphorylation reached peak activations at 2.5 and 15 min, respectively. Only in HCEC, pharmacological manipulation of KCC activity modified the hypotonicity-induced activation of p44/42MAPK, whereas p38MAPK phosphorylation was insensitive to such procedures in both cell lines. Larger increases in HCEC KCC1 membrane protein content correlated with their ability to undergo faster and more complete RVD. Furthermore, pharmacological activation of KCC increased p44/42MAPK phosphorylation in HCEC but not in RCEC, presumably a reflection of low KCC1 membrane expression in RCEC. These findings suggest that KCC1 plays a role in (i) maintaining isotonic steady-state cell volume homeostasis, (ii) recovery of isotonic cell volume after a hypotonic challenge through RVD, and (iii) regulating hypotonicity-induced activation of the p44/42MAPK signaling pathway required for cell proliferation.
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Affiliation(s)
- José E. Capó-Aponte
- Department of Biological Sciences, State University of New York, State College of Optometry, New York, NY 10036, USA
| | - Zheng Wang
- Department of Biological Sciences, State University of New York, State College of Optometry, New York, NY 10036, USA
| | - Victor N. Bildin
- Department of Biological Sciences, State University of New York, State College of Optometry, New York, NY 10036, USA
| | - Pavel Iserovich
- Department of Ophthalmology, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
| | - Zan Pan
- Department of Biological Sciences, State University of New York, State College of Optometry, New York, NY 10036, USA
| | - Fan Zhang
- Department of Biological Sciences, State University of New York, State College of Optometry, New York, NY 10036, USA
| | - Kathryn S. Pokorny
- The Institute of Ophthalmology & Visual Science, New Jersey Medical School, University of Medicine & Dentistry, Newark, NJ 07101, USA
| | - Peter S. Reinach
- Department of Biological Sciences, State University of New York, State College of Optometry, New York, NY 10036, USA
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Gong N, Ecke I, Mergler S, Yang J, Metzner S, Schu S, Volk HD, Pleyer U, Ritter T. Gene transfer of cyto-protective molecules in corneal endothelial cells and cultured corneas: analysis of protective effects in vitro and in vivo. Biochem Biophys Res Commun 2007; 357:302-7. [PMID: 17416348 DOI: 10.1016/j.bbrc.2007.03.146] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Accepted: 03/23/2007] [Indexed: 11/16/2022]
Abstract
The loss of corneal endothelial cells plays a critical role in many corneal diseases and is a common phenomenon following cornea transplantation. In addition, the non-regenerative capacity of human corneal endothelial cells (HCEC) ultimately requires appropriate protection of corneal tissues during ex vivo storage to ensure vitality of the cells. However, only 70% of donor corneas can be used for grafting because of endothelial deficiencies. Corneal endothelial cell loss during storage is mainly induced by apoptotic cell death. This study was undertaken, for proof of principle, to investigate whether over-expression of cyto-protective molecules Bcl-x(L), Bag-1, and HO-1 prevents the loss of corneal endothelial cells both in vitro and in vivo. We demonstrate that gene transfer of both Bcl-x(L) and HO-1 has cyto-protective effects on HCEC in vitro. However, gene transfer of a single cyto-protective molecule does not prevent its rejection upon transplantation in a MHC class I/II disparate rat model.
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Affiliation(s)
- Nianqiao Gong
- Department of Ophthalmology, Charité-University Medicine Berlin, Germany
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17
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Mergler S, Pleyer U. The human corneal endothelium: new insights into electrophysiology and ion channels. Prog Retin Eye Res 2007; 26:359-78. [PMID: 17446115 DOI: 10.1016/j.preteyeres.2007.02.001] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The corneal endothelium is a monolayer that mediates the flux of solutes and water across the posterior corneal surface. Thereby, it plays an essential role to maintain the transparency of the cornea. Unlike the epithelium, the human endothelium is an amitotic cell layer with a critical cell density and the risk of corneal decompensation. The number of endothelial cells subsequently decreases with age. Moreover, the endothelial cell loss is accelerated after various impairments such as surgical trauma (e.g. cataract extraction) and following corneal transplantation. This cell loss is associated with programmed cell death (apoptosis) and changed ion channel activity. However, little is known about the electrophysiology and ion channel expression (in particular Ca2+ channels) in corneal endothelial cells. This article reviews our current knowledge about the electrophysiology of the corneal endothelium. It highlights ion channel expression, which may have a major role in corneal cell physiology and pathological events. A better understanding of the (electro)physiological function of the cornea may lead to the development of clinical relevant new therapeutic and preventive measures.
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Affiliation(s)
- Stefan Mergler
- Department of Ophthalmology, Charité-University Medicine Berlin, Campus Virchow-Clinic, Augustenburger Platz 1, 13353 Berlin, Germany.
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Tsugane M, Nagai Y, Kimura Y, Oka JI, Kimura H. Differentiated astrocytes acquire sensitivity to hydrogen sulfide that is diminished by the transformation into reactive astrocytes. Antioxid Redox Signal 2007; 9:257-69. [PMID: 17115938 DOI: 10.1089/ars.2007.9.257] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Hydrogen sulfide (H2S) enhances the induction of hippocampal long-term potentiation (LTP) and induces calcium waves in astrocytes. Based on these observations, H2S has been proposed to be a synaptic modulator in the brain. Here we show that differentiated astrocytes acquire sensitivity to H2S that is diminished by their transformation into reactive astrocytes. Although sodium hydrosulfide hydrate (NaHS), a donor of H2S, did not increase the intracellular concentration of Ca2+ in progenitors, exposure of progenitors to leukemia inhibitory factor (LIF), which induces differentiation into glial fibrillary acidic protein (GFAP)-positive astrocytes, greatly increased the sensitivity to NaHS. In contrast, epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), dibutyryl cyclic AMP (db cAMP) and interleukin-1beta (IL-1beta) induced the conversion to reactive astrocytes with diminished sensitivity to NaHS. This suppressive effect of EGF on the sensitivity to NaHS was inhibited by cycloheximide, indicating that de novo protein synthesis was required for the suppression of H2S sensitivity.
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Affiliation(s)
- Mamiko Tsugane
- National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan
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19
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Mergler S, Strowski MZ, Kaiser S, Plath T, Giesecke Y, Neumann M, Hosokawa H, Kobayashi S, Langrehr J, Neuhaus P, Plöckinger U, Wiedenmann B, Grötzinger C. Transient receptor potential channel TRPM8 agonists stimulate calcium influx and neurotensin secretion in neuroendocrine tumor cells. Neuroendocrinology 2007; 85:81-92. [PMID: 17426390 DOI: 10.1159/000101693] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2006] [Accepted: 02/22/2007] [Indexed: 12/28/2022]
Abstract
TRPM8 is a member of the melastatin-type transient receptor potential ion channel family. Activation by cold or by agonists (menthol, icilin) induces a transient rise in intracellular free calcium concentration ([Ca(2+)](i)). Our previous study demonstrated that Ca(2+)-permeable cation channels play a role in IGF-1-induced secretion of chromogranin A in human neuroendocrine tumor (NET) cell line BON [Mergler et al.: Neuroendocrinology 2006;82:87-102]. Here, we extend our earlier study by investigating the expression of TRPM8 and characterizing its impact on [Ca(2+)](i) and the secretion of neurotensin (NT). We identified TRPM8 expression in NET BON cells by RT-PCR, Western blotting and immunofluorescence staining. Icilin increased [Ca(2+)](i) in TRPM8-transfected human embryonic kidney cells (HEK293) but not in mock-transfected cells. Icilin and menthol induced Ca(2+) transients in BON cells as well as in primary NET cell cultures of two different pancreatic NETs as detected by single cell fluorescence imaging. Icilin increased non-selective cation channel currents in BON cells as detected by patch-clamp recordings. This activation was associated with increased NT secretion. Taken together, this study demonstrates for the first time the expression TRPM8 in NET cells and its role in regulating [Ca(2+)](i) and NT secretion. The regulation of NT secretion in NETs by TRPM8 may have a potential clinical implication in diagnosis or therapy.
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Affiliation(s)
- Stefan Mergler
- Department of Internal Medicine, Division of Hepatology and Gastroenterology, Charité - Universitatsmedizin Berlin, Campus Virchow Klinikum, Berlin, Germany.
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20
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Franklin RA, Rodriguez-Mora OG, Lahair MM, McCubrey JA. Activation of the calcium/calmodulin-dependent protein kinases as a consequence of oxidative stress. Antioxid Redox Signal 2006; 8:1807-17. [PMID: 16987033 DOI: 10.1089/ars.2006.8.1807] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Oxygen radicals have diverse effects on cells. In many cases, exposure to reactive oxygen intermediates (ROI) can induce cell death. Conversely, there is also evidence that suggests oxygen radicals can activate signaling pathways that are thought to prevent cell death. In this review, the authors discuss the finding that hydrogen peroxide and ROI-generating treatments trigger the activation of the calcium/calmodulin-dependent kinases (CaM-kinases), and the potential role this activation has in preventing apoptosis. Evidence is presented that CaM-kinase activation occurs by both calcium dependent- and independent-pathways in response to ROIs. In addition, the idea is discussed that ROIs have the potential to lead to the phosphorylation of calmodulin and through this mechanism potentiate the activation of the CaM-kinases. The concept that inhibition of the CaM-kinases as a mechanism to sensitize cells to the damaging effects of ROIs is also presented. Contrasting these studies, evidence is presented that exposure of the CaM-kinases directly to hydrogen peroxide also has the apparent ability to inhibit their activity.
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Affiliation(s)
- Richard A Franklin
- Department of Microbiology and Immunology, and the Leo W. Jenkins Cancer Center, Brody School of Medicine at East Carolina University, Greenville, North Carolina 27834, USA
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Abstract
Among the 28 identified and unique mammalian TRP (transient receptor potential) channel isoforms, at least 19 are expressed in vascular endothelial cells. These channels appear to participate in a diverse range of vascular functions, including control of vascular tone, regulation of vascular permeability, mechanosensing, secretion, angiogenesis, endothelial cell proliferation, and endothelial cell apoptosis and death. Malfunction of these channels may result in disorders of the human cardiovascular system. All TRP channels, except for TRPM4 and TRPM5, are cation channels that allow Ca2+ influx. However, there is a daunting diversity in the mode of activation and regulation in each case. Specific TRP channels may be activated by different stimuli such as vasoactive agents, oxidative stress, mechanical stimuli, and heat. TRP channels may then transform these stimuli into changes in the cytosolic Ca2+, which are eventually coupled to various vascular responses. Evidence has been provided to suggest the involvement of at least the following TRP channels in vascular function: TRPC1, TRPC4, TRPC6, and TRPV1 in the control of vascular permeability; TRPC4, TRPV1, and TRPV4 in the regulation of vascular tone; TRPC4 in hypoxia-induced vascular remodeling; and TRPC3, TRPC4, and TRPM2 in oxidative stress-induced responses. However, in spite of the large body of data available, the functional role of many endothelial TRP channels is still poorly understood. Elucidating the mechanisms regulating the different endothelial TRP channels, and the associated development of drugs selectively to target the different isoforms, as a means to treat cardiovascular disease should, therefore, be a high priority.
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Affiliation(s)
- Xiaoqiang Yao
- Department of Physiology, Chinese University of Hong Kong, China.
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22
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Yang H, Mergler S, Sun X, Wang Z, Lu L, Bonanno JA, Pleyer U, Reinach PS. TRPC4 knockdown suppresses epidermal growth factor-induced store-operated channel activation and growth in human corneal epithelial cells. J Biol Chem 2005; 280:32230-7. [PMID: 16033767 PMCID: PMC4096720 DOI: 10.1074/jbc.m504553200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Epidermal growth factor (EGF) in corneal epithelial cells stimulates proliferation by inducing capacitative calcium entry (CCE). However, neither the identity nor the mechanism of activation of the plasma membrane influx pathway that mediates CCE is known. Accordingly, we determined, in human corneal epithelial cells, whether or not (i) CCE is dependent upon stimulation of storeoperated channel (SOC) activity, (ii) the canonical transient receptor potential (TRP) protein isoform TRPC4 is a component of such channels, and (iii) suppression of TRPC4 protein expression decreases EGF-induced stimulation of SOC activity and proliferation. The whole cell patch-clamp technique was used to monitor TRPC4-mediated stimulation of SOC activity following intracellular calcium store depletion and induction of CCE. TRPC4 small interfering RNA transfection suppressed TRPC4 protein expression. Reverse transcription-PCR and Western blot analysis were used to assess knockdown efficiency of mRNA and protein expression. [(3)H]Thymidine incorporation was used to evaluate EGF-in-duced mitogenesis. Ca(2+) transients were measured by single-cell fluorescence imaging. TRPC4 knockdown decreased mRNA and protein expression by 89 and 87%, respectively. In these cells, EGF-induced SOC activation elicited by intracellular calcium store depletion was obviated; 2) EGF-induced CCE fell by 76%; 3) EGF-induced stimulation of SOC activity was eliminated; and 4) EGF-induced increases in proliferation fell by 54%. Thus, TRPC4 is a component of SOC in human corneal epithelial cells whose activation by EGF is requisite for an optimum mitogenic response to this growth factor.
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Affiliation(s)
- Hua Yang
- College of Optometry, State University of New York, New York, New York 10036
| | - Stefan Mergler
- Eye Clinic, Charité University Medicine, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Xingcai Sun
- School of Optometry, Indiana University, Bloomington, Indiana 47405
| | - Zheng Wang
- College of Optometry, State University of New York, New York, New York 10036
| | - Luo Lu
- Division of Molecular Medicine, Harbor-UCLA Medical Center, Torrance, California 90502
| | | | - Uwe Pleyer
- Eye Clinic, Charité University Medicine, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Peter S. Reinach
- College of Optometry, State University of New York, New York, New York 10036
- To whom correspondence should be addressed: College of Optometry, State University of New York, 33 West 42nd St., New York, NY 10036. Tel.: 212-780-5165; Fax: 212-780-5174;
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