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Youngblood H, Schoenlein PV, Pasquale LR, Stamer WD, Liu Y. Estrogen dysregulation, intraocular pressure, and glaucoma risk. Exp Eye Res 2023; 237:109725. [PMID: 37956940 PMCID: PMC10842791 DOI: 10.1016/j.exer.2023.109725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 10/20/2023] [Accepted: 11/08/2023] [Indexed: 11/19/2023]
Abstract
Characterized by optic nerve atrophy due to retinal ganglion cell (RGC) death, glaucoma is the leading cause of irreversible blindness worldwide. Of the major risk factors for glaucoma (age, ocular hypertension, and genetics), only elevated intraocular pressure (IOP) is modifiable, which is largely regulated by aqueous humor outflow through the trabecular meshwork. Glucocorticoids such as dexamethasone have long been known to elevate IOP and lead to glaucoma. However, several recent studies have reported that steroid hormone estrogen levels inversely correlate with glaucoma risk, and that variants in estrogen signaling genes have been associated with glaucoma. As a result, estrogen dysregulation may contribute to glaucoma pathogenesis, and estrogen signaling may protect against glaucoma. The mechanism for estrogen-related protection against glaucoma is not completely understood but likely involves both regulation of IOP homeostasis and neuroprotection of RGCs. Based upon its known activities, estrogen signaling may promote IOP homeostasis by affecting extracellular matrix turnover, focal adhesion assembly, actin stress fiber formation, mechanosensation, and nitric oxide production. In addition, estrogen receptors in the RGCs may mediate neuroprotective functions. As a result, the estrogen signaling pathway may offer a therapeutic target for both IOP control and neuroprotection. This review examines the evidence for a relationship between estrogen and IOP and explores the possible mechanisms by which estrogen maintains IOP homeostasis.
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Affiliation(s)
- Hannah Youngblood
- Department of Cellular Biology and Anatomy, Augusta University, Augusta, GA, USA
| | - Patricia V Schoenlein
- Department of Cellular Biology and Anatomy, Augusta University, Augusta, GA, USA; Department of Radiology and Georgia Cancer Center, Augusta University, Augusta, GA, USA; Department of Surgery, Augusta University, Augusta, GA, USA
| | - Louis R Pasquale
- Department of Ophthalmology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - W Daniel Stamer
- Department of Ophthalmology and Biomedical Engineering, Duke University, Durham, NC, USA
| | - Yutao Liu
- Department of Cellular Biology and Anatomy, Augusta University, Augusta, GA, USA; James and Jean Culver Vision Discovery Institute, Medical College of Georgia, Augusta University, Augusta, GA, USA; Center for Biotechnology and Genomic Medicine, Augusta University, Augusta, GA, USA.
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García-López C, Gómez-Huertas C, Sánchez-González JM, Borroni D, Rodríguez-Calvo-de-Mora M, Romano V, Rachwani-Anil R, Ramos-López JF, Ortiz-Pérez S, Rocha-de-Lossada C. Opioids and Ocular Surface Pathology; A Literature Review of New Treatments Horizons. J Clin Med 2022; 11:jcm11051424. [PMID: 35268515 PMCID: PMC8911328 DOI: 10.3390/jcm11051424] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 03/02/2022] [Accepted: 03/03/2022] [Indexed: 12/01/2022] Open
Abstract
This review discusses the role of opioids in the corneal surface and the different pathways and therapeutic methods of management. A literature review was performed using PubMed database. For the database search, the main searching words “opioid” and “topical opioid treatment” were used with the descriptors “cornea”, “ocular surface”, “neuropathic corneal pain”, “corneal sensitivity” and “naltrexone”; original scientific articles and reviews were included to achieve the purpose of the review. The endogenous opioid system has relevant functions in the organism, and in daily use, opioids are used as painkillers. However, these drugs may be employed for other indications as opioid pathways have a wide spectrum. The corneal surface for topical treatment is easily accessible, hence sparing the side effects of systemic opioids. Instillation of opioid antagonist substances, such as naltrexone, increases corneal healing rates and stimulates the division of corneal epithelium cells without deleterious effects. The natural modulation of endogenous opioids controls different forms of pain, including inflammatory and neuropathic pain, both in the ocular surface and in the central nervous system. There are diverse methods in controlling pain using opioids, especially in refractory forms. This review attempts to collect the literature about corneal surface and opioid pathways to provide an overview image and a possible direction of the news treatments.
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Affiliation(s)
- Celia García-López
- Department of Ophthalmology, Hospital Universitario Virgen de las Nieves, 18014 Granada, Spain; (C.G.-L.); (C.G.-H.); (J.-F.R.-L.); (S.O.-P.); (C.R.-d.-L.)
| | - Carmen Gómez-Huertas
- Department of Ophthalmology, Hospital Universitario Virgen de las Nieves, 18014 Granada, Spain; (C.G.-L.); (C.G.-H.); (J.-F.R.-L.); (S.O.-P.); (C.R.-d.-L.)
| | - José-María Sánchez-González
- Department of Physics of Condensed Matter, Optics Area, University of Seville, 41004 Seville, Spain
- Correspondence: ; Tel.: +34-955-42-08-61
| | - Davide Borroni
- Department of Doctoral Studies, Riga Stradins University, LV-1007 Riga, Latvia;
- Cornea Research Unit, ADVALIA Vision, 20145 Milan, Italy
| | - Marina Rodríguez-Calvo-de-Mora
- Department of Ophthalmology, Hospital Regional Universitario de Málaga, 29010 Málaga, Spain;
- Department of Ophthalmology (Qvision), Vithas Almería, 04120 Almería, Spain
| | - Vito Romano
- Department of Eye and Vision Science Ophthalmology, St Paul’s Eye Hospital, Liverpool L7 8XP, UK;
- Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool L69 3BX, UK
- Department of Medical and Surgical Specialties, Radiological Sciences, and Public Health, Ophthalmology Clinic, University of Brescia, 25121 Brescia, Italy
| | | | - Juan-Francisco Ramos-López
- Department of Ophthalmology, Hospital Universitario Virgen de las Nieves, 18014 Granada, Spain; (C.G.-L.); (C.G.-H.); (J.-F.R.-L.); (S.O.-P.); (C.R.-d.-L.)
| | - Santiago Ortiz-Pérez
- Department of Ophthalmology, Hospital Universitario Virgen de las Nieves, 18014 Granada, Spain; (C.G.-L.); (C.G.-H.); (J.-F.R.-L.); (S.O.-P.); (C.R.-d.-L.)
- Department of Surgery, Faculty of Medicine, University of Granada, 18010 Granada, Spain
| | - Carlos Rocha-de-Lossada
- Department of Ophthalmology, Hospital Universitario Virgen de las Nieves, 18014 Granada, Spain; (C.G.-L.); (C.G.-H.); (J.-F.R.-L.); (S.O.-P.); (C.R.-d.-L.)
- Department of Ophthalmology (Qvision), Vithas Almería, 04120 Almería, Spain
- Department of Ophthalmology, Ceuta Medical Center, 51001 Ceuta, Spain
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3
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Identification of Estrogen Signaling in a Prioritization Study of Intraocular Pressure-Associated Genes. Int J Mol Sci 2021; 22:ijms221910288. [PMID: 34638643 PMCID: PMC8508848 DOI: 10.3390/ijms221910288] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 09/20/2021] [Accepted: 09/22/2021] [Indexed: 12/12/2022] Open
Abstract
Elevated intraocular pressure (IOP) is the only modifiable risk factor for primary open-angle glaucoma (POAG). Herein we sought to prioritize a set of previously identified IOP-associated genes using novel and previously published datasets. We identified several genes for future study, including several involved in cytoskeletal/extracellular matrix reorganization, cell adhesion, angiogenesis, and TGF-β signaling. Our differential correlation analysis of IOP-associated genes identified 295 pairs of 201 genes with differential correlation. Pathway analysis identified β-estradiol as the top upstream regulator of these genes with ESR1 mediating 25 interactions. Several genes (i.e., EFEMP1, FOXC1, and SPTBN1) regulated by β-estradiol/ESR1 were highly expressed in non-glaucomatous human trabecular meshwork (TM) or Schlemm’s canal (SC) cells and specifically expressed in TM/SC cell clusters defined by single-cell RNA-sequencing. We confirmed ESR1 gene and protein expression in human TM cells and TM/SC tissue with quantitative real-time PCR and immunofluorescence, respectively. 17β-estradiol was identified in bovine, porcine, and human aqueous humor (AH) using ELISA. In conclusion, we have identified estrogen receptor signaling as a key modulator of several IOP-associated genes. The expression of ESR1 and these IOP-associated genes in TM/SC tissue and the presence of 17β-estradiol in AH supports a role for estrogen signaling in IOP regulation.
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Jin J, Xu GX, Yuan ZL. Influence of the hypothalamic arcuate nucleus on intraocular pressure and the role of opioid peptides. PLoS One 2014; 9:e82315. [PMID: 24691128 PMCID: PMC3972173 DOI: 10.1371/journal.pone.0082315] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 10/22/2013] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND An opioid peptide neuron/humoral feedback regulation might be involved in changes of intraocular pressure (IOP). The aims of this study are to investigate the effects of arcuate nucleus (ARC) and opioid peptides on intraocular pressure (IOP). METHODS Fifty-four healthy purebred New Zealand white rabbits (108 eyes) were randomly divided into 4 groups, including control group, electrical stimulation group, [D-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin (DAMGO) group, and [D-Pen 2, D-Pen5]- enkephalin (DPDPE) group. Bilateral IOP was measured after unilateral electrical stimulation of the ARC or unilateral microinjection into the ARC of the selective μ-opioid receptor agonist DAMGO or the selective δ opioid receptor agonist DPDPE, both alone and after pre-administration of either the non-selective opioid receptor antagonist naloxone or saline. RESULTS Both electrical stimulation in ARC and micro-injection either or opioid receptor agonists, DAMGO or DPDPE, respectively, caused a significant bilateral reduction in IOP (P<0.05) which was more pronounced in the ipsilateral than in the contralateral eye. Pretreatment with naloxone prevented some, but not all IOP reductions. CONCLUSION The ARC takes part in the negative regulation of IOP, an action that may involve opioid neurons.
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Affiliation(s)
- Ji Jin
- Department of Ophthalmology, the Second Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China
| | - Guo-xu Xu
- Department of Ophthalmology, the Second Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China
| | - Zhi-lan Yuan
- Department of Ophthalmology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu Province, China
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Goel R, Murthy KR, Srikanth SM, Pinto SM, Bhattacharjee M, Kelkar DS, Madugundu AK, Dey G, Mohan SS, Krishna V, Prasad TK, Chakravarti S, Harsha HC, Pandey A. Characterizing the normal proteome of human ciliary body. Clin Proteomics 2013; 10:9. [PMID: 23914977 PMCID: PMC3750387 DOI: 10.1186/1559-0275-10-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 07/16/2013] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The ciliary body is the circumferential muscular tissue located just behind the iris in the anterior chamber of the eye. It plays a pivotal role in the production of aqueous humor, maintenance of the lens zonules and accommodation by changing the shape of the crystalline lens. The ciliary body is the major target of drugs against glaucoma as its inhibition leads to a drop in intraocular pressure. A molecular study of the ciliary body could provide a better understanding about the pathophysiological processes that occur in glaucoma. Thus far, no large-scale proteomic investigation has been reported for the human ciliary body. RESULTS In this study, we have carried out an in-depth LC-MS/MS-based proteomic analysis of normal human ciliary body and have identified 2,815 proteins. We identified a number of proteins that were previously not described in the ciliary body including importin 5 (IPO5), atlastin-2 (ATL2), B-cell receptor associated protein 29 (BCAP29), basigin (BSG), calpain-1 (CAPN1), copine 6 (CPNE6), fibulin 1 (FBLN1) and galectin 1 (LGALS1). We compared the plasma proteome with the ciliary body proteome and found that the large majority of proteins in the ciliary body were also detectable in the plasma while 896 proteins were unique to the ciliary body. We also classified proteins using pathway enrichment analysis and found most of proteins associated with ubiquitin pathway, EIF2 signaling, glycolysis and gluconeogenesis. CONCLUSIONS More than 95% of the identified proteins have not been previously described in the ciliary body proteome. This is the largest catalogue of proteins reported thus far in the ciliary body that should provide new insights into our understanding of the factors involved in maintaining the secretion of aqueous humor. The identification of these proteins will aid in understanding various eye diseases of the anterior segment such as glaucoma and presbyopia.
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Affiliation(s)
- Renu Goel
- Institute of Bioinformatics, International Technology Park, Bangalore 560 066, India.,Department of Biotechnology, Kuvempu University, Shankaraghatta, Shimoga 577 451, Karnataka, India
| | - Krishna R Murthy
- Institute of Bioinformatics, International Technology Park, Bangalore 560 066, India.,Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam 690 525, Kerala, India.,Vittala International Institute Of Ophthalmology, Bangalore 560 085, Karnataka, India
| | - Srinivas M Srikanth
- Institute of Bioinformatics, International Technology Park, Bangalore 560 066, India.,Centre of Excellence in Bioinformatics, Bioinformatics Centre, School of Life Sciences, Pondicherry University, Puducherry 605 014, India
| | - Sneha M Pinto
- Institute of Bioinformatics, International Technology Park, Bangalore 560 066, India.,Manipal University, Madhav Nagar, Manipal 576104, Karnataka, India
| | - Mitali Bhattacharjee
- Institute of Bioinformatics, International Technology Park, Bangalore 560 066, India.,Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam 690 525, Kerala, India
| | - Dhanashree S Kelkar
- Institute of Bioinformatics, International Technology Park, Bangalore 560 066, India.,Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam 690 525, Kerala, India
| | - Anil K Madugundu
- Institute of Bioinformatics, International Technology Park, Bangalore 560 066, India
| | - Gourav Dey
- Institute of Bioinformatics, International Technology Park, Bangalore 560 066, India
| | - Sujatha S Mohan
- Institute of Bioinformatics, International Technology Park, Bangalore 560 066, India.,Department of Biotechnology, Kuvempu University, Shankaraghatta, Shimoga 577 451, Karnataka, India.,Research Unit for Immunoinformatics, RIKEN Research Center for Allergy and Immunology, RIKEN Yokohama Institute, Kanagawa 230 0045, Japan
| | - Venkatarangaiah Krishna
- Department of Biotechnology, Kuvempu University, Shankaraghatta, Shimoga 577 451, Karnataka, India
| | - Ts Keshava Prasad
- Institute of Bioinformatics, International Technology Park, Bangalore 560 066, India.,Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam 690 525, Kerala, India.,Manipal University, Madhav Nagar, Manipal 576104, Karnataka, India
| | - Shukti Chakravarti
- Johns Hopkins University School of Medicine, Baltimore 21205, MD, USA.,Department of Cell Biology, Johns Hopkins School of Medicine, Baltimore, MD, USA.,Department of Ophthalmology, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - H C Harsha
- Institute of Bioinformatics, International Technology Park, Bangalore 560 066, India
| | - Akhilesh Pandey
- Johns Hopkins University School of Medicine, Baltimore 21205, MD, USA.,McKusick-Nathans Institute of Genetic Medicine, Departments of Biological Chemistry, Oncology and Pathology, Johns Hopkins University School of Medicine, Baltimore 21205, MD, USA
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Luo N, Kumar A, Conwell M, Weinreb RN, Anderson R, Sun Y. Compensatory Role of Inositol 5-Phosphatase INPP5B to OCRL in Primary Cilia Formation in Oculocerebrorenal Syndrome of Lowe. PLoS One 2013; 8:e66727. [PMID: 23805271 PMCID: PMC3689662 DOI: 10.1371/journal.pone.0066727] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 05/10/2013] [Indexed: 12/11/2022] Open
Abstract
Inositol phosphatases are important regulators of cell signaling, polarity, and vesicular trafficking. Mutations in OCRL, an inositol polyphosphate 5-phosphatase, result in Oculocerebrorenal syndrome of Lowe, an X-linked recessive disorder that presents with congenital cataracts, glaucoma, renal dysfunction and mental retardation. INPP5B is a paralog of OCRL and shares similar structural domains. The roles of OCRL and INPP5B in the development of cataracts and glaucoma are not understood. Using ocular tissues, this study finds low levels of INPP5B present in human trabecular meshwork but high levels in murine trabecular meshwork. In contrast, OCRL is localized in the trabecular meshwork and Schlemm's canal endothelial cells in both human and murine eyes. In cultured human retinal pigmented epithelial cells, INPP5B was observed in the primary cilia. A functional role for INPP5B is revealed by defects in cilia formation in cells with silenced expression of INPP5B. This is further supported by the defective cilia formation in zebrafish Kupffer's vesicles and in cilia-dependent melanosome transport assays in inpp5b morphants. Taken together, this study indicates that OCRL and INPP5B are differentially expressed in the human and murine eyes, and play compensatory roles in cilia development.
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Affiliation(s)
- Na Luo
- Glick Eye Institute, Department of Ophthalmology, Department of Biochemistry and Cell Biology, Department of Dermatology, Indiana University Indianapolis, Indiana, United States of America
| | - Akhilesh Kumar
- Glick Eye Institute, Department of Ophthalmology, Department of Biochemistry and Cell Biology, Department of Dermatology, Indiana University Indianapolis, Indiana, United States of America
| | - Michael Conwell
- Glick Eye Institute, Department of Ophthalmology, Department of Biochemistry and Cell Biology, Department of Dermatology, Indiana University Indianapolis, Indiana, United States of America
| | - Robert N. Weinreb
- Department of Ophthalmology, University of California San Diego, San Diego, California, United States of America
| | - Ryan Anderson
- Department of Pediatrics, Indiana University Indianapolis, Indiana,United States of America
| | - Yang Sun
- Glick Eye Institute, Department of Ophthalmology, Department of Biochemistry and Cell Biology, Department of Dermatology, Indiana University Indianapolis, Indiana, United States of America
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Saccà SC, Roszkowska AM, Izzotti A. Environmental light and endogenous antioxidants as the main determinants of non-cancer ocular diseases. Mutat Res 2013; 752:153-171. [PMID: 23337404 DOI: 10.1016/j.mrrev.2013.01.001] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 01/10/2013] [Accepted: 01/11/2013] [Indexed: 02/03/2023]
Abstract
The human eye is constantly exposed to sunlight and artificial lighting. Exogenous sources of reactive oxygen species (ROS) such as UV light, visible light, ionizing radiation, chemotherapeutics, and environmental toxins contribute to oxidative damage in ocular tissues. Long-term exposure to these insults places the aging eye at considerable risk for pathological consequences of oxidative stress. Furthermore, in eye tissues, mitochondria are an important endogenous source of ROS. Over time, all ocular structures, from the tear film to the retina, undergo oxidative stress, and therefore, the antioxidant defenses of each tissue assume the role of a safeguard against degenerative ocular pathologies. The ocular surface and cornea protect the other ocular tissues and are significantly exposed to oxidative stress of environmental origin. Overwhelming of antioxidant defenses in these tissues clinically manifests as pathologies including pterygium, corneal dystrophies, and endothelial Fuch's dystrophy. The crystalline lens is highly susceptible to oxidative damage in aging because its cells and their intracellular proteins are not turned over or replaced, thus providing the basis for cataractogenesis. The trabecular meshwork, which is the anterior chamber tissue devoted to aqueous humor drainage, has a particular susceptibility to mitochondrial oxidative injury that affects its endothelium and leads to an intraocular pressure increase that marks the beginning of glaucoma. Photo-oxidative stress can cause acute or chronic retinal damage. The pathogenesis of age-related macular degeneration involves oxidative stress and death of the retinal pigment epithelium followed by death of the overlying photoreceptors. Accordingly, converging evidence indicates that mutagenic mechanisms of environmental and endogenous sources play a fundamental pathogenic role in degenerative eye diseases.
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Affiliation(s)
- Sergio C Saccà
- Department of Head/Neck Pathologies, St Martino Hospital, Ophthalmology unit, Genoa, Italy
| | - Anna Maria Roszkowska
- Department of Specialized Surgery, University Hospital, Ophthalmology Unit, Messina, Italy
| | - Alberto Izzotti
- Department of Health Sciences, University of Genoa, Via A. Pastore 1, I-16132, Genoa, Italy.
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Abstract
This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, Flushing, NY 11367, United States.
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Kaufman PL, Rasmussen CA. Advances in glaucoma treatment and management: outflow drugs. Invest Ophthalmol Vis Sci 2012; 53:2495-500. [PMID: 22562850 DOI: 10.1167/iovs.12-9483m] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Affiliation(s)
- Paul L Kaufman
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin 53705-2135, USA.
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Ellis DZ. Guanylate cyclase activators, cell volume changes and IOP reduction. Cell Physiol Biochem 2011; 28:1145-54. [PMID: 22179003 DOI: 10.1159/000335866] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/06/2011] [Indexed: 11/19/2022] Open
Abstract
Glaucoma afflicts millions of people worldwide and is a major cause of blindness. The risk to develop glaucoma is enhanced by increases in IOP, which result from deranged flow of aqueous humor. Aqueous humor is a fluid located in the front of the eye that gives the eye its buoyancy and supplies nutrients to other eye tissues. Aqueous humor is secreted by a tissue called ciliary processes and exits the eye via two tissues; the trabecular meshwork (TM) and Schlemm's canal. Because the spaces through which the fluid flows get smaller as the TM joins the area of the Schlemm's canal, there is resistance to aqueous humor outflow and this resistance creates IOP. There is a correlation between changes in TM and Schlemm's canal cell volume and rates of aqueous humor outflow; agents that decrease TM and Schlemm's canal cell volume, increase the rate of aqueous humor outflow, thus decreasing IOP. IOP is regulated by guanylate cyclase activators as shown in humans, rabbits and monkeys. There are two distinct groups of guanylate cyclases, membrane guanylate cyclase and soluble guanylate cyclase (sGC); activation of both have been shown to decrease IOP. Members of the membrane guanylate cyclase family of receptors bind to peptide ligands, while the sGC responds to gases (such as NO and CO(2)) and compounds (such as YC1, [3-(5'-hydroxymethyl-2'furyl)-1-benzyl indazole), a benzyl indazole derivative, and BAY-58-2667); activation of either results in formation of cyclic GMP (cGMP) and activation of protein kinase G (PKG) and subsequent phosphorylation of target proteins, including the high conductance calcium activated potassium channel (BKca channel). While activators of both membrane guanylate cyclase and sGC have the ability to lower IOP, the IOP lowering effects of sGC are noteworthy because sGC activators can be topically applied to the eye to achieve an effect. We have demonstrated that activators of sGC increase the rate at which aqueous humor exits the eye in a time course that correlates with the time course for sGC-induced decreases in TM and Schlemm's canal cell volume. Additionally, sGC-induced decrease in cell volume is accompanied by both K(+) and Cl(-) efflux induced by activation of K(+) and Cl(-) channels, including the BKca channel and/or K(+)Cl(-) symport. This suggests that parallel K(+)Cl(-) efflux, and resultant H(2)O efflux result in decreases in cell volume. These observations suggest a functional role for sGC activators, and suggest that the sGC/cGMP/PKG systems are potential therapeutic targets in the treatment of glaucoma.
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Affiliation(s)
- Dorette Z Ellis
- Department of Pharmacodynamics, University of Florida, Gainesville, FL 32610, USA.
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