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Zhang C, Jiao Q, Wang M, Zhu Z, Zhao J, Zheng Y. High correlated color temperature artificial lighting impairs retinal pigment epithelium integrity and chloride ion transport: A potential mechanism for choroidal thinning. Biochem Biophys Res Commun 2024; 718:150078. [PMID: 38735140 DOI: 10.1016/j.bbrc.2024.150078] [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: 03/21/2024] [Revised: 04/04/2024] [Accepted: 05/07/2024] [Indexed: 05/14/2024]
Abstract
Among the environmental factors contributing to myopia, the role of correlated color temperature (CCT) of ambient light emerges as a key element warranting in-depth investigation. The choroid, a highly vascularized and dynamic structure, often undergoes thinning during the progression of myopia, though the precise mechanism remains elusive. The retinal pigment epithelium (RPE), the outermost layer of the retina, plays a pivotal role in regulating the transport of ion and fluid between the subretinal space and the choroid. A hypothesis suggests that variations in choroidal thickness (ChT) may be modulated by transepithelial fluid movement across the RPE. Our experimental results demonstrate that high CCT illumination significantly compromised the integrity of tight junctions in the RPE and disrupted chloride ion transport. This functional impairment of the RPE may lead to a reduction in fluid transfer across the RPE, consequently resulting in choroidal thinning and potentially accelerating axial elongation. Our findings provide support for the crucial role of the RPE in regulating ChT. Furthermore, we emphasize the potential hazards posed by high CCT artificial illumination on the RPE, the choroid, and refractive development, underscoring the importance of developing eye-friendly artificial light sources to aid in the prevention and control of myopia.
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Affiliation(s)
- Chenchen Zhang
- Department of Ophthalmology, The Second Hospital of Jilin University, Changchun, 130041, PR China
| | - Qing Jiao
- Department of Ophthalmology, The Second Hospital of Jilin University, Changchun, 130041, PR China
| | - Mingxuan Wang
- Department of Ophthalmology, The Second Hospital of Jilin University, Changchun, 130041, PR China
| | - Zhe Zhu
- State Key Laboratory Cultivation Base, Shandong Provincial Key Laboratory of Ophthalmology, Eye Institute of Shandong First Medical University, Qingdao, 266000, PR China
| | - Jing Zhao
- Department of Ophthalmology, The Second Hospital of Jilin University, Changchun, 130041, PR China
| | - Yajuan Zheng
- Department of Ophthalmology, The Second Hospital of Jilin University, Changchun, 130041, PR China.
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Zhu Y, Garcia-Sanchez J, Dalal R, Sun Y, Kapiloff MS, Goldberg JL, Liu WW. Differential expression of PIEZO1 and PIEZO2 mechanosensitive channels in ocular tissues implicates diverse functional roles. Exp Eye Res 2023; 236:109675. [PMID: 37820892 PMCID: PMC10843266 DOI: 10.1016/j.exer.2023.109675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 10/08/2023] [Accepted: 10/08/2023] [Indexed: 10/13/2023]
Abstract
PIEZO1 and PIEZO2 are mechanosensitive ion channels that regulate many important physiological processes including vascular blood flow, touch, and proprioception. As the eye is subject to mechanical stress and is highly perfused, these channels may play important roles in ocular function and intraocular pressure regulation. PIEZO channel expression in the eye has not been well defined, in part due to difficulties in validating available antibodies against PIEZO1 and PIEZO2 in ocular tissues. It is also unclear if PIEZO1 and PIEZO2 are differentially expressed. To address these questions, we used single-molecule fluorescence in situ hybridization (smFISH) together with transgenic reporter mice expressing PIEZO fusion proteins under the control of their endogenous promoters to compare the expression and localization of PIEZO1 and PIEZO2 in mouse ocular tissues relevant to glaucoma. We detected both PIEZO1 and PIEZO2 expression in the trabecular meshwork, ciliary body, and in the ganglion cell layer (GCL) of the retina. Piezo1 mRNA was more abundantly expressed than Piezo2 mRNA in these ocular tissues. Piezo1 but not Piezo2 mRNA was detected in the inner nuclear layer and outer nuclear layer of the retina. Our results suggest that PIEZO1 and PIEZO2 are differentially expressed and may have distinct roles as mechanosensors in glaucoma-relevant ocular tissues.
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Affiliation(s)
- Ying Zhu
- Spencer Center for Vision Research, Byers Eye Institute, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Julian Garcia-Sanchez
- Spencer Center for Vision Research, Byers Eye Institute, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Roopa Dalal
- Spencer Center for Vision Research, Byers Eye Institute, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Yang Sun
- Spencer Center for Vision Research, Byers Eye Institute, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Michael S Kapiloff
- Spencer Center for Vision Research, Byers Eye Institute, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Jeffrey L Goldberg
- Spencer Center for Vision Research, Byers Eye Institute, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Wendy W Liu
- Spencer Center for Vision Research, Byers Eye Institute, Stanford University School of Medicine, Palo Alto, CA, USA.
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Li KL, Shan SW, Lin FY, Ling CY, Wong NW, Li HL, Han W, To CH, Do CW. Regulation of Aqueous Humor Secretion by Melatonin in Porcine Ciliary Epithelium. Int J Mol Sci 2023; 24:5789. [PMID: 36982863 PMCID: PMC10051954 DOI: 10.3390/ijms24065789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 03/10/2023] [Accepted: 03/16/2023] [Indexed: 03/30/2023] Open
Abstract
Secretion of melatonin, a natural hormone whose receptors are present in the ciliary epithelium, displays diurnal variation in the aqueous humor (AH), potentially contributing to the regulation of intraocular pressure. This study aimed to determine the effects of melatonin on AH secretion in porcine ciliary epithelium. The addition of 100 µM melatonin to both sides of the epithelium significantly increased the short-circuit current (Isc) by ~40%. Stromal administration alone had no effect on the Isc, but aqueous application triggered a 40% increase in Isc, similar to that of bilateral application without additive effect. Pre-treatment with niflumic acid abolished melatonin-induced Isc stimulation. More importantly, melatonin stimulated the fluid secretion across the intact ciliary epithelium by ~80% and elicited a sustained increase (~50-60%) in gap junctional permeability between pigmented ciliary epithelial (PE) cells and non-pigmented ciliary epithelial (NPE) cells. The expression of MT3 receptor was found to be >10-fold higher than that of MT1 and MT2 in porcine ciliary epithelium. Aqueous pre-treatment with MT1/MT2 antagonist luzindole failed to inhibit the melatonin-induced Isc response, while MT3 antagonist prazosin pre-treatment abolished the Isc stimulation. We conclude that melatonin facilitates Cl- and fluid movement from PE to NPE cells, thereby stimulating AH secretion via NPE-cell MT3 receptors.
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Affiliation(s)
- Ka-Lok Li
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China
| | - Sze-Wan Shan
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China
- Centre for Eye and Vision Research (CEVR), 17W Hong Kong Science Park, Hong Kong, China
- Research Centre for SHARP Vision (RCSV), The Hong Kong Polytechnic University, Hong Kong, China
| | - Fang-Yu Lin
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China
- Department of Ophthalmology, Zhejiang University, Hangzhou 310027, China
- Department of Ophthalmology, Emory University, Atlanta, GA 30322, USA
| | - Choi-Ying Ling
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China
| | - Nga-Wai Wong
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China
| | - Hoi-Lam Li
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China
- Centre for Eye and Vision Research (CEVR), 17W Hong Kong Science Park, Hong Kong, China
| | - Wei Han
- Department of Ophthalmology, Zhejiang University, Hangzhou 310027, China
| | - Chi-Ho To
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China
- Centre for Eye and Vision Research (CEVR), 17W Hong Kong Science Park, Hong Kong, China
- Research Centre for SHARP Vision (RCSV), The Hong Kong Polytechnic University, Hong Kong, China
| | - Chi-Wai Do
- School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China
- Centre for Eye and Vision Research (CEVR), 17W Hong Kong Science Park, Hong Kong, China
- Research Centre for SHARP Vision (RCSV), The Hong Kong Polytechnic University, Hong Kong, China
- Research Institute of Smart Ageing (RISA), The Hong Kong Polytechnic University, Hong Kong, China
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Sabirov RZ, Islam MR, Okada T, Merzlyak PG, Kurbannazarova RS, Tsiferova NA, Okada Y. The ATP-Releasing Maxi-Cl Channel: Its Identity, Molecular Partners and Physiological/Pathophysiological Implications. Life (Basel) 2021; 11:life11060509. [PMID: 34073084 PMCID: PMC8229958 DOI: 10.3390/life11060509] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 05/27/2021] [Indexed: 12/18/2022] Open
Abstract
The Maxi-Cl phenotype accounts for the majority (app. 60%) of reports on the large-conductance maxi-anion channels (MACs) and has been detected in almost every type of cell, including placenta, endothelium, lymphocyte, cardiac myocyte, neuron, and glial cells, and in cells originating from humans to frogs. A unitary conductance of 300-400 pS, linear current-to-voltage relationship, relatively high anion-to-cation selectivity, bell-shaped voltage dependency, and sensitivity to extracellular gadolinium are biophysical and pharmacological hallmarks of the Maxi-Cl channel. Its identification as a complex with SLCO2A1 as a core pore-forming component and two auxiliary regulatory proteins, annexin A2 and S100A10 (p11), explains the activation mechanism as Tyr23 dephosphorylation at ANXA2 in parallel with calcium binding at S100A10. In the resting state, SLCO2A1 functions as a prostaglandin transporter whereas upon activation it turns to an anion channel. As an efficient pathway for chloride, Maxi-Cl is implicated in a number of physiologically and pathophysiologically important processes, such as cell volume regulation, fluid secretion, apoptosis, and charge transfer. Maxi-Cl is permeable for ATP and other small signaling molecules serving as an electrogenic pathway in cell-to-cell signal transduction. Mutations at the SLCO2A1 gene cause inherited bone and gut pathologies and malignancies, signifying the Maxi-Cl channel as a perspective pharmacological target.
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Affiliation(s)
- Ravshan Z. Sabirov
- Division of Cell Signaling, National Institute for Physiological Sciences (NIPS), Okazaki 444-8787, Japan; (M.R.I.); (T.O.); (P.G.M.); (R.S.K.); (N.A.T.)
- Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent 100174, Uzbekistan
- Correspondence: (R.Z.S.); (Y.O.); Tel.: +81-46-858-1501 (Y.O.); Fax: +81-46-858-1542 (Y.O.)
| | - Md. Rafiqul Islam
- Division of Cell Signaling, National Institute for Physiological Sciences (NIPS), Okazaki 444-8787, Japan; (M.R.I.); (T.O.); (P.G.M.); (R.S.K.); (N.A.T.)
- Department of Biochemistry and Molecular Biology, Jagannath University, Dhaka 1100, Bangladesh
| | - Toshiaki Okada
- Division of Cell Signaling, National Institute for Physiological Sciences (NIPS), Okazaki 444-8787, Japan; (M.R.I.); (T.O.); (P.G.M.); (R.S.K.); (N.A.T.)
- Veneno Technologies Co. Ltd., Tsukuba 305-0031, Japan
| | - Petr G. Merzlyak
- Division of Cell Signaling, National Institute for Physiological Sciences (NIPS), Okazaki 444-8787, Japan; (M.R.I.); (T.O.); (P.G.M.); (R.S.K.); (N.A.T.)
- Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent 100174, Uzbekistan
| | - Ranokhon S. Kurbannazarova
- Division of Cell Signaling, National Institute for Physiological Sciences (NIPS), Okazaki 444-8787, Japan; (M.R.I.); (T.O.); (P.G.M.); (R.S.K.); (N.A.T.)
- Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent 100174, Uzbekistan
| | - Nargiza A. Tsiferova
- Division of Cell Signaling, National Institute for Physiological Sciences (NIPS), Okazaki 444-8787, Japan; (M.R.I.); (T.O.); (P.G.M.); (R.S.K.); (N.A.T.)
- Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent 100174, Uzbekistan
| | - Yasunobu Okada
- Division of Cell Signaling, National Institute for Physiological Sciences (NIPS), Okazaki 444-8787, Japan; (M.R.I.); (T.O.); (P.G.M.); (R.S.K.); (N.A.T.)
- Department of Physiology, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
- Department of Physiology, School of Medicine, Aichi Medical University, Nagakute 480-1195, Japan
- Correspondence: (R.Z.S.); (Y.O.); Tel.: +81-46-858-1501 (Y.O.); Fax: +81-46-858-1542 (Y.O.)
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Zhang H, Wong CL, Shan SW, Li KK, Cheng AK, Lee KL, Ge J, To CH, Do CW. Characterisation of Cl‐ transporter and channels in experimentally induced myopic chick eyes. Clin Exp Optom 2021; 94:528-35. [DOI: 10.1111/j.1444-0938.2011.00611.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Affiliation(s)
- Hengli Zhang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat‐Sen University, China
- The Centre for Myopia Research, School of Optometry and the
| | - Chun Lung Wong
- The Centre for Myopia Research, School of Optometry and the
| | - Sze Wan Shan
- The Centre for Myopia Research, School of Optometry and the
| | - King Kit Li
- The Centre for Myopia Research, School of Optometry and the
| | - Angela K Cheng
- The Centre for Myopia Research, School of Optometry and the
| | - Kam Len Lee
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong SAR, China, E‐mail:
| | - Jian Ge
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat‐Sen University, China
| | - Chi Ho To
- The Centre for Myopia Research, School of Optometry and the
| | - Chi Wai Do
- The Centre for Myopia Research, School of Optometry and the
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Sabirov RZ, Merzlyak PG, Islam MR, Okada T, Okada Y. The properties, functions, and pathophysiology of maxi-anion channels. Pflugers Arch 2016; 468:405-20. [DOI: 10.1007/s00424-015-1774-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 12/11/2015] [Accepted: 12/15/2015] [Indexed: 01/19/2023]
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Zhong Y, Yang Z, Huang WC, Luo X. Adenosine, adenosine receptors and glaucoma: An updated overview. Biochim Biophys Acta Gen Subj 2013; 1830:2882-90. [DOI: 10.1016/j.bbagen.2013.01.005] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 12/21/2012] [Accepted: 01/07/2013] [Indexed: 01/30/2023]
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Abstract
Epithelia involved in vectorial salt transport respond to apical and basolateral changes in osmotic activity by moderating the transmural solute transport rate simultaneously with underlying volume regulatory mechanisms involved in regulatory volume increase (RVI) and decrease (RVD). This review examines rapid osmotic responses in salt secreting epithelia of marine and euryhaline teleost fish, with inclusion of recent results from other ion transporting epithelia that also respond rapidly to osmotic shock. Mitochondrion-rich chloride secreting cells of marine teleost fish gills and skin, when exposed to hypertonic shock, activate NaCl secretion via phosphorylation of Na(+), K(+), 2Cl(-) cotransporter (NKCC1) in the basolateral membrane and activation of anion channels in the apical membrane. Conversely, NaCl secretion is inhibited when chloride secreting cells are swollen osmotically. Mammalian airway epithelial cells also possess NKCC1 basally and apical anion channels [Cystic Fibrosis Transmembrane conductance Regulator (CFTR)]; with hypotonic shock, this epithelium releases ATP and NaCl secretion is stimulated via purinergic receptors, while hypertonic shock inhibits Na(+) uptake. In the eye, the ciliary epithelium activates Cl(-) channels in response to hypotonic shock as RVD, an effect that modulates transepithelial fluid transport rates. In the renal A6 cell line, K(+) and Cl(-) effluxes activate during RVD and RVI Na(+) transepithelial absorption. A common theme in these systems is ATP release in hypotonic shock with subsequent RVD-effective mechanisms such as NKCC1 inhibition and K(+) and Cl(-) efflux, but there are different effects of osmotic changes on transepithelial transport, apparently depending on the role of the epithelial system.
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Affiliation(s)
- W S Marshall
- Department of Biology, Saint Francis Xavier University, Antigonish, NS, Canada B2G 2W5.
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Chen J, Runyan SA, Robinson MR. Novel ocular antihypertensive compounds in clinical trials. Clin Ophthalmol 2011; 5:667-77. [PMID: 21629573 PMCID: PMC3104796 DOI: 10.2147/opth.s15971] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Indexed: 01/31/2023] Open
Abstract
Introduction: Glaucoma is a multifactorial disease characterized by progressive optic nerve injury and visual field defects. Elevated intraocular pressure (IOP) is the most widely recognized risk factor for the onset and progression of open-angle glaucoma, and IOP-lowering medications comprise the primary treatment strategy. IOP elevation in glaucoma is associated with diminished or obstructed aqueous humor outflow. Pharmacotherapy reduces IOP by suppressing aqueous inflow and/or increasing aqueous outflow. Purpose: This review focuses on novel non-FDA approved ocular antihypertensive compounds being investigated for IOP reduction in ocular hypertensive and glaucoma patients in active clinical trials within approximately the past 2 years. Methods: The mode of IOP reduction, pharmacology, efficacy, and safety of these new agents were assessed. Relevant drug efficacy and safety trials were identified from searches of various scientific literature databases and clinical trial registries. Compounds with no specified drug class, insufficient background information, reformulations, and fixed-combinations of marketed drugs were not considered. Results: The investigational agents identified comprise those that act on the same targets of established drug classes approved by the FDA (ie, prostaglandin analogs and β-adrenergic blockers) as well as agents belonging to novel drug classes with unique mechanisms of action. Novel targets and compounds evaluated in clinical trials include an actin polymerization inhibitor (ie, latrunculin), Rho-associated protein kinase inhibitors, adenosine receptor analogs, an angiotensin II type 1 receptor antagonist, cannabinoid receptor agonists, and a serotonin receptor antagonist. Conclusion: The clinical value of novel compounds for the treatment of glaucoma will depend ultimately on demonstrating favorable efficacy and benefit-to-risk ratios relative to currently approved prostaglandin analogs and β-blockers and/or having complementary modes of action.
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Affiliation(s)
- June Chen
- Department of Biological Sciences, Allergan, Inc., 2525 Dupont Dr., Irvine, CA 92612, USA.
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Avni I, Garzozi HJ, Barequet IS, Segev F, Varssano D, Sartani G, Chetrit N, Bakshi E, Zadok D, Tomkins O, Litvin G, Jacobson KA, Fishman S, Harpaz Z, Farbstein M, Bar Yehuda S, Silverman MH, Kerns WD, Bristol DR, Cohn I, Fishman P. Treatment of dry eye syndrome with orally administered CF101: data from a phase 2 clinical trial. Ophthalmology 2010; 117:1287-93. [PMID: 20304499 PMCID: PMC3668568 DOI: 10.1016/j.ophtha.2009.11.029] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Revised: 10/16/2009] [Accepted: 11/13/2009] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE To explore the safety and efficacy of CF101, an A(3) adenosine receptor agonist, in patients with moderate to severe dry eye syndrome. DESIGN Phase 2, multicenter, randomized, double-masked, placebo-controlled, parallel-group study. PARTICIPANTS Sixty-eight patients completed the study, 35 patients in the placebo group and 33 patients in the CF101 group. INTERVENTION Patients were treated orally with either 1 mg CF101 pills or matching vehicle-filled placebo pills, given twice daily for 12 weeks, followed by a 2-week posttreatment observation. MAIN OUTCOME MEASURES An improvement of more than 25% over baseline at week 12 in one of the following parameters: (1) tear break-up time (BUT); (2) superficial punctate keratitis assessed by fluorescein staining results; and (3) Schirmer tear test 1 results. Clinical laboratory safety tests, ophthalmic examinations, intraocular pressure (IOP) measurements, electrocardiographic evaluations, vital sign measurements, and monitoring of adverse events. RESULTS A statistically significant increase in the proportion of patients who achieved more than 25% improvement in the corneal staining and in the clearance of corneal staining was noted between the CF101-treated group and the placebo group. Treatment with CF101 resulted in a statistically significant improvement in the mean change from baseline at week 12 of the corneal staining, BUT, and tear meniscus (TM) height in the CF101-treated group. CF101 was well tolerated and exhibited an excellent safety profile with no serious adverse events. A statistically significant decrease from baseline was observed in the IOP of the CF101-treated group in comparison with the placebo group. CONCLUSIONS CF101, given orally, induced a statistically significant improvement in the corneal staining and an improvement in the BUT and TM in patients with moderate to severe dry eye syndrome. The drug was very well tolerated. These data and the anti-inflammatory characteristic of CF101 support further study of the drug as a potential treatment for the signs and symptoms of dry eye syndrome. FINANCIAL DISCLOSURE(S) Proprietary or commercial disclosure may be found after the references.
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Affiliation(s)
- Isaac Avni
- Assaf Harofe Medical Center, Zeriffin, Beer Yaakov, Israel
| | | | - Irina S. Barequet
- Goldschleger Eye Institute, Sheba Medical Center, Sackler Faculty of Medicine, Tel Hashomer, Israel
| | | | | | | | - Noa Chetrit
- Assaf Harofe Medical Center, Zeriffin, Beer Yaakov, Israel
| | - Erez Bakshi
- Assaf Harofe Medical Center, Zeriffin, Beer Yaakov, Israel
| | - David Zadok
- Assaf Harofe Medical Center, Zeriffin, Beer Yaakov, Israel
| | | | | | - Kenneth A. Jacobson
- National Inst. of Diabetes & Digestive & Kidney Diseases, NIH, Bethesda, MD, USA
| | | | | | | | | | | | | | | | - Ilan Cohn
- Can-Fite BioPharma Ltd, Petach Tikva, Israel
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Sabirov RZ, Okada Y. The maxi-anion channel: a classical channel playing novel roles through an unidentified molecular entity. J Physiol Sci 2009; 59:3-21. [PMID: 19340557 PMCID: PMC10717152 DOI: 10.1007/s12576-008-0008-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Accepted: 11/05/2008] [Indexed: 10/20/2022]
Abstract
The maxi-anion channel is widely expressed and found in almost every part of the body. The channel is activated in response to osmotic cell swelling, to excision of the membrane patch, and also to some other physiologically and pathophysiologically relevant stimuli, such as salt stress in kidney macula densa as well as ischemia/hypoxia in heart and brain. Biophysically, the maxi-anion channel is characterized by a large single-channel conductance of 300-400 pS, which saturates at 580-640 pS with increasing the Cl(-) concentration. The channel discriminates well between Na(+) and Cl(-), but is poorly selective to other halides exhibiting weak electric-field selectivity with an Eisenman's selectivity sequence I. The maxi-anion channel has a wide pore with an effective radius of approximately 1.3 nm and permits passage not only of Cl(-) but also of some intracellular large organic anions, thereby releasing major extracellular signals and gliotransmitters such as glutamate(-) and ATP(4-). The channel-mediated efflux of these signaling molecules is associated with kidney tubuloglomerular feedback, cardiac ischemia/hypoxia, as well as brain ischemia/hypoxia and excitotoxic neurodegeneration. Despite the ubiquitous expression, well-defined properties and physiological/pathophysiological significance of this classical channel, the molecular entity has not been identified. Molecular identification of the maxi-anion channel is an urgent task that would greatly promote investigation in the fields not only of anion channel but also of physiological/pathophysiological signaling in the brain, heart and kidney.
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Affiliation(s)
- Ravshan Z. Sabirov
- Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki, 444-8585 Japan
- Laboratory of Molecular Physiology, Institute of Physiology and Biophysics, Tashkent, 100095 Uzbekistan
| | - Yasunobu Okada
- Department of Cell Physiology, National Institute for Physiological Sciences, Okazaki, 444-8585 Japan
- Department of Physiological Sciences, School of Life Science, The Graduate University for Advanced Studies (Sokendai), Okazaki, 444-8585 Japan
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Abstract
Cell volume perturbation initiates a wide array of intracellular signalling cascades, leading to protective and adaptive events and, in most cases, activation of volume-regulatory osmolyte transport, water loss, and hence restoration of cell volume and cellular function. Cell volume is challenged not only under physiological conditions, e.g. following accumulation of nutrients, during epithelial absorption/secretion processes, following hormonal/autocrine stimulation, and during induction of apoptosis, but also under pathophysiological conditions, e.g. hypoxia, ischaemia and hyponatremia/hypernatremia. On the other hand, it has recently become clear that an increase or reduction in cell volume can also serve as a specific signal in the regulation of physiological processes such as transepithelial transport, cell migration, proliferation and death. Although the mechanisms by which cell volume perturbations are sensed are still far from clear, significant progress has been made with respect to the nature of the sensors, transducers and effectors that convert a change in cell volume into a physiological response. In the present review, we summarize recent major developments in the field, and emphasize the relationship between cell volume regulation and organism physiology/pathophysiology.
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Affiliation(s)
- I H Lambert
- Department of Biology, University of Copenhagen, Copenhagen, Denmark.
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13
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Zhang Y, Davidson BR, Stamer WD, Barton JK, Marmorstein LY, Marmorstein AD. Enhanced inflow and outflow rates despite lower IOP in bestrophin-2-deficient mice. Invest Ophthalmol Vis Sci 2008; 50:765-70. [PMID: 18936135 DOI: 10.1167/iovs.08-2501] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Bestrophin-2 (Best2), a putative Cl(-) channel is expressed in the nonpigmented epithelium (NPE). Disruption of Best2 in mice results in a diminished intraocular pressure (IOP). Aqueous humor dynamics were compared in Best2(+/+) and Best2(-/-) mice, to better understand the contribution of Best2 to IOP. METHODS Measurements of IOP, episcleral venous pressure (EVP), conventional outflow facility (C(t)), aqueous humor production (F(a)), and anterior chamber volume (V(a)) were made using anterior chamber cannulation. Conventional (F(c)) and uveoscleral outflow (F(u)), and rate of aqueous humor turnover, were calculated from measured data. The anterior chamber was examined in live mice by optical coherence tomography (OCT) and postmortem by light microscopy. RESULTS IOP in Best2(-/-) mice was lower compared with Best2(+/+) littermates. EVP was unchanged. Since Best2 is expressed in NPE cells, the hypothesis was that Best2 is involved in generating aqueous flow. However, F(a) in Best2(-/-) mice was increased by approximately 73% compared with Best2(+/+) mice. This was accompanied by increases in F(c) and F(u). Aqueous humor turnover was enhanced more than twofold in Best2(-/-) mice. No evidence of developmental structural changes was noted. CONCLUSIONS Best2 appears to antagonize the formation of aqueous humor and cause an inhibition of both F(c) and F(u), despite being expressed only in NPE cells. These data support the hypothesis that the inflow and outflow pathways communicate via soluble agents present in the aqueous humor and implicate Best2 as a critical mediator of that communication.
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Affiliation(s)
- Youwen Zhang
- Department of Ophthalmology and Vision Science, University of Arizona, Tucson, Arizona 85711, USA
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Mathias RT, White TW, Brink PR. Chapter 3 The Role of Gap Junction Channels in the Ciliary Body Secretory Epithelium. CURRENT TOPICS IN MEMBRANES 2008. [DOI: 10.1016/s1063-5823(08)00403-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Chapter 13 Outflow Signaling Mechanisms and New Therapeutic Strategies for the Control of Intraocular Pressure. CURRENT TOPICS IN MEMBRANES 2008. [DOI: 10.1016/s1063-5823(08)00413-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Markovskaya A, Crooke A, Guzmán-Aranguez AI, Peral A, Ziganshin AU, Pintor J. Hypotensive effect of UDP on intraocular pressure in rabbits. Eur J Pharmacol 2007; 579:93-7. [PMID: 18031728 DOI: 10.1016/j.ejphar.2007.10.040] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2007] [Revised: 10/11/2007] [Accepted: 10/16/2007] [Indexed: 11/30/2022]
Abstract
Nucleotides can modify intraocular pressure (IOP). We have tested the ability of uridine-5'-diphosphate, UDP, for modulating IOP in New Zealand white rabbits. Uridine 5' diphosphate, UDP, reduced IOP by 82.9+/-2.6% compared to control. Dose-response analysis demonstrated a concentration dependent pattern which presented a pD(2) value of 7.57+/-1.45, equivalent to an EC(50) of 26.91 nM. Of all the tested P2 receptor antagonists, suramin, pyridoxalphosphate-6-azophenyl-2, 4-disulfonic acid (PPADS) and Reactive Blue 2 (RB-2), only the last two were able to reverse the action triggered by UDP. Altogether, UDP acting probably on P2Y(6) receptors present on the ciliary processes, can reduce intraocular pressure, indicating that this substance may be used for the treatment of ocular hypertension and glaucoma.
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Affiliation(s)
- Anna Markovskaya
- Department of Pharmacology, Kazan State Medical University, Kazan, Russia
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